critical thinking questions about earth

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4: How does Earth's interior work, and how does it affect the surface? Scientists want to figure out more about the past and future of the constant convective motion of Earth's mantle and core, which triggers volcanism, mountain building and seafloor formation.

5: Why does Earth have plate tectonics and continents? Scientists wonder why Earth has plates, constantly on the move, and how closely tectonics are related to the abundance of water, continents, oceans and life.

6: How are Earth processes controlled by material properties? The big movers and shakers on Earth, including plate tectonics , arise from the atomic structure and other properties of Earth materials, so scientists want to know more about these properties.

7: What causes climate to change – and how much can it change? Deeper study of the history of Earth's climate could help scientists predict the magnitude and consequences of today's climate change .

8: How has life shaped Earth – and how has Earth shaped life? The interactions between geology and biology are key to understanding life's role in injecting oxygen into the atmosphere, mass extinctions and the course of evolution.

9: Can earthquakes, volcanic eruptions and their consequences be predicted? Scientists still don't know how fault ruptures start and stop, and how magma moves beneath Earth's surface.

10: How do fluid flow and transport affect the human environment? Scientists are unclear about how fluids move underground. More knowledge about this will help with management of natural resources and the environment.

The report was requested by the U.S. Department of Energy, National Science Foundation, U.S. Geological Survey, and NASA .

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Earth Systems Interacting - Critical Thinking Activity

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Scientists break down Earth’s major systems into four; the geosphere, hydrosphere, atmosphere, and biosphere . These systems interact in multiple ways to affect Earth’s surface materials and processes.

In this activity, choose the systems that are working together to create the following phenomenon.

Earth Systems Interacting - Critical Thinking Activity

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Fulfillment of next generation science standards (ngss), grade 5 - 5-ess2 earth’s systems ngss disciplinary core ideas.

ESS2.A: Earth Materials and Systems • Earth’s major systems are the geosphere (solid and molten rock, soil, and sediments), the hydrosphere (water and ice), the atmosphere (air), and the biosphere (living things, including humans). These systems interact in multiple ways to affect Earth’s surface materials and processes. The ocean supports a variety of ecosystems and organisms, shapes landforms, and influences climate. Winds and clouds in the atmosphere interact with the landforms to determine patterns of weather. (5-ESS2-1)

ESS2.C: The Roles of Water in Earth’s Surface Processes • Nearly all of Earth’s available water is in the ocean. Most fresh water is in glaciers or underground; only a tiny fraction is in streams, lakes, wetlands, and the atmosphere. (5-ESS2-2)

Performance Expectations Students who demonstrate understanding can: 5-ESS2-1. Develop a model using an example to describe ways the geosphere, biosphere, hydrosphere, and/or atmosphere interact. [Clarification Statement: Examples could include the influence of the ocean on ecosystems, landform shape, and climate; the influence of the atmosphere on landforms and ecosystems through weather and climate; and the influence of mountain ranges on winds and clouds in the atmosphere. The geosphere, hydrosphere, atmosphere, and biosphere are each a system.] [Assessment Boundary: Assessment is limited to the interactions of two systems at a time.] 5-ESS2-2. Describe and graph the amounts and percentages of water and fresh water in various reservoirs to provide evidence about the distribution of water on Earth. [Assessment Boundary: Assessment is limited to oceans, lakes, rivers, glaciers, ground water, and polar ice caps, and does not include the atmosphere.]

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Critical Thinking Questions

Explain the relationship between Earth’s ancient atmosphere and the evolution of some of the first life forms on Earth. Use the terms anaerobicandphototrophic, and explain the effect of cyanobacteria on the atmosphere.

Phototrophic organisms appeared during the first two billion years of Earth’s existence. Anaerobic organisms appeared within one billion years of Earth’s formation. From these organisms evolved the cyanobacteria which that produce oxygen as a by-product of photosynthesis, leading to the oxygenation of the atmosphere.
For the first two billion years of Earth’s existence, the atmosphere had no molecular oxygen. Thus, the first organisms were anaerobic. Cyanobacteria appeared within one billion years of Earth’s formation. From these evolved the phototrophic organisms that produce oxygen as a by-product of photosynthesis, leading to the oxygenation of the atmosphere.
For the first two billion years of Earth’s existence, the atmosphere had no molecular oxygen. Thus, the first organisms were anaerobic. Phototrophic organisms appeared within one billion years of Earth’s formation. From these organisms evolved the cyanobacteria, which produce oxygen as a by-product of photosynthesis, leading to the oxygenation of the atmosphere.
For the first two billion years of Earth’s existence, the atmosphere had no molecular oxygen. Thus, the first organisms were anaerobic. Cyanobacteria that produce oxygen as a by-product of photosynthesis, leading to the oxygenation of the atmosphere, appeared within one billion years of Earth’s formation. From these organisms evolved phototrophic organisms.

Describe briefly how you would detect the presence of a non culturable prokaryote in an environmental sample.

Recombinant DNA techniques are used to detect the presence of a nonculturable prokaryote in an environmental sample. Polymerase chain reaction is used to amplify selected portions of prokaryotic DNA.
Molecular biology techniques are used to detect the presence of a nonculturable prokaryote in an environmental sample. Electrophoresis is used to amplify selected portions of prokaryotic DNA.
Molecular biology techniques are used to detect the presence of a nonculturable prokaryote in an environmental sample. Polymerase chain reaction is used to amplify selected portions of prokaryotic DNA.
Recombinant DNA techniques are used to detect the presence of a nonculturable prokaryote in an environmental sample. Electrophoresis is used to amplify selected portions of prokaryotic DNA.

Why do scientists believe that the first organisms on Earth were extremophiles?

Earth’s early environment was full of extreme places with much oxygen in the atmosphere, no ozone to shield Earth’s surface from mutagenic radiation, much geologic upheaval, and volcanic activity. Extremophiles are bacteria and archaea that are adapted to grow in extreme environments.
Earth’s early environment was full of extreme places with little oxygen in the atmosphere, no ozone to shield Earth’s surface from mutagenic radiation, much geologic upheaval, and volcanic activity. Extremophiles are bacteria and archaea that are adapted to grow in extreme environments.
Earth’s early environment was full of extreme places with little oxygen in the atmosphere, no ozone to shield Earth’s surface from mutagenic radiation, less geologic upheaval, and volcanic activity. Extremophiles are bacteria and archaea that are adapted to grow in extreme environments.
For the first two billion years of Earth’s existence, the atmosphere had no molecular oxygen.

Describe a typical prokaryotic cell.

It has a cell wall enclosing cell membrane, cytoplasm, ribosomes, and nucleoid region with genetic material. It may have a protective capsule, flagellum, pili, and plasmids.
It has a cell wall enclosing cell membrane, cytoplasm, ribosomes, and nucleus containing genetic material. It may have a protective capsule, flagellum, pili, and plasmids.
It has a cell wall enclosing nuclear membrane, cytoplasm, ribosomes, and nucleoid region with genetic material. It may have a protective capsule, flagellum, pili, and plasmids.
It has a cell wall enclosing nuclear membrane, cytoplasm, mitochondria, vacuoles, and nucleoid region with genetic material. It may have a protective capsule, flagellum, pili, and plasmids.

Explain the statement that both Archaea and Bacteria have the same basic structures, but these structures are built from different chemical components.

Typical cells in Archaea and Bacteria contain a cell wall, cell membrane, nucleoid region, ribosomes, and often a capsule, flagellum, and pili. However, these are sometimes made from different chemical compounds make them. Cell walls of Bacteria contain peptidoglycan while Archaea do not. Plasma membrane lipids of Bacteria are fatty acids while those of Archaea are phytanyl groups.
Typical cells in Archaea and Bacteria contain a cell wall, cell membrane, nucleoid region, and often a capsule, flagellum, and pili, but in some instances, different chemical compounds make them. Cell walls of Bacteria contain peptidoglycan while Archaea do not. Bacteria contain 70S ribosomes while Archaea contain 80S ribosomes.
Typical cells in Archaea and Bacteria contain a cell wall, nuclear membranes, nucleoid region, and often a capsule, flagellum, and pili, but in some instances, different chemical compounds make them. Cell walls of Bacteria contain peptidoglycan while Archaea do not. Plasma membrane lipids of bacteria are fatty acids, while the plasma membrane lipids of Archaea are phytanyl groups.
Typical cells in Archaea and Bacteria contain a cell wall, cell membrane, nucleoid region, and often a capsule, flagellum, and pili, but in some instances, different chemical compounds make them. Cell walls of Bacteria contain peptidoglycan while Archaea do not. Plasma membrane lipids of Bacteria are phytanyl groups, while the plasma membrane lipids of Archaea are fatty acids.

Three basic prokaryotic categories are cocci, spirilli, and bacilli. Describe the basic structural features of each category.

These three prokaryote groups have similar basic structural features. They typically have cell walls enclosing nuclear membranes, cytoplasm, ribosomes, mitochondria, and nucleoid region with genetic material. They may have a protective capsule, flagellum, pili, and plasmids.
Cocci and spirilli have similar basic structural features. They typically have cell walls enclosing cell membranes, a flagellum for locomotion, and pili for attachment. Bacilli are rod shaped which contain ribosomes and a nucleoid region with genetic material.
These three prokaryote groups have similar basic structural features. They typically have cell walls enclosing cell membranes, cytoplasm, ribosomes, and a nucleoid region with chromosomes. They may have a protective capsule, flagellum, pili, and plasmids.
Bacilli and spirilli have similar basic structural features. They typically have cell walls enclosing nuclear membranes, a flagellum for locomotion, and pili for attachment. Cocci are spherical containing ribosomes and a nucleoid region with genetic material.

Which macronutrient do you think is most important? What evidence can you offer to support your choice?

Carbon because it represents 12 percent of the total dry weight of a typical cell and is a component of all macromolecules.
Oxygen because it is necessary and is a major component for all macromolecules. It also accounts for 50 percent of the total composition of a cell.
Carbon because it is necessary and is a major component for all macromolecules. It also accounts for 50 percent of the total composition of a cell.
Nitrogen because it is necessary and is a major component for all macromolecules. It also accounts for 50 percent of the total composition of a cell.

A bacterium requires only a particular amino acid as an organic nutrient and lives in a completely lightless environment. What mode of nutrition—free energy and carbon—does it use? Justify your response.

Chemoheterotroph, as it must rely on chemical sources of energy living in a lightless environment and a heterotroph if it uses organic compounds for its carbon source.
Chemoorganotroph, as it must rely on chemical sources of energy living in a lightless environment and an organotroph if it uses organic compounds other than carbon dioxide for its carbon source.
Chemolitoautotroph, as it must rely on chemical sources of energy living in a lightless environment and an autotroph if it uses organic compounds other than carbon dioxide for its carbon source.
Chemoheterotroph, as it must rely on chemical sources of energy living in a lightless environment and a heterotroph if it uses organic compounds other than carbon dioxide for its carbon source.

Assuming that you could synthesize all of the nitrogen-containing compounds needed if you had nitrogen, what might you eat for a typical meal if you could fix nitrogen like some prokaryotes?

My meal might be fruits or vegetables, bread, and water as nitrogen is present in the highest amount in water.
My meal might be fruits or vegetables, water, bread, and air as atmospheric nitrogen could be simply absorbed.
My meal might be fruits or vegetables, cheese, meat, water, bread, and air as atmospheric nitrogen could be simply absorbed.
My meal might be cheese or meat, water, bread, and air as atmospheric nitrogen could be simply absorbed.

Identify and discuss a bacterial disease that caused a historically important plague or epidemic. What is the modern distribution of this disease?

Bubonic plague caused by Yersinia pestis was a pandemic that occurred in the fourteenth century. In modern times, there are only about 100 cases of bubonic plague each year. The bacterium responds well to modern antibiotics.
Bubonic plague caused by Yersinia enterocolitica was a pandemic that occurred in the fourteenth century. In modern times, there are about 1,000 to 3,000 cases of bubonic plague each year. The bacterium responds well to modern antibiotics.
Pneumonic plague caused by Yersinia pestis was a pandemic that occurred in the fourteenth century. In modern times, there are about 1,000 to 3,000 cases of pneumonic plague each year. The bacterium responds well to modern antibiotics.
Bubonic plague caused by Yersinia pestis was a pandemic that occurred in the fourteenth century. In modern times, there are about 1,000 to 3,000 cases of bubonic plague each year. The bacterium responds well to modern antibiotics.
Yes, better sterilization and canning procedures have reduced the incidence of botulism. Most cases of foodborne illness now are related to small-scale food production.
No, better sterilization and canning procedures have reduced the incidence of botulism. Most cases of foodborne illness now are related to small-scale food production.
No, better sterilization and canning procedures have increased the incidence of botulism. Most cases of foodborne illnesses now are related to large-scale food production.
Yes, better sterilization and canning procedures have reduced the incidence of botulism. Most cases of foodborne illnesses now are related to large-scale food production.

What was the Plague of Athens? What is the modern distribution of this disease?

The Plague of Athens was a disease caused by Yersinia pestis that killed one-quarter of Athenian troops in 430 B.C. Between 10 and 15 million cases of typhoid fever occur today, resulting in over 10, 000 deaths annually.
The Plague of Athens was a disease caused by Salmonella entericaserovar typhi that killed one-quarter of Athenian troops in 430 B.C. Between 5 and 10 million cases of typhoid fever occur today, resulting in over 20,000 deaths annually.
The Plague of Athens was a disease caused by Yersinia pestis that killed one-quarter of Athenian troops in 430 B.C. Between 16 and 33 million cases of typhoid fever occur today, resulting in over 200,000 deaths annually.
The Plague of Athens was a disease caused by Salmonella entericaserovar typhi that killed one-quarter of Athenian troops in 430 B.C. Between 16 and 33 million cases of typhoid fever occur today, resulting in over 200,000 deaths annually.

Why is the processing of foods with prokaryotes considered an example of early biotechnology?

Prokaryotes have been used to only make specific food products like cheese, wine, bread, beer, and yogurt since before the term biotechnology was coined.
Prokaryotes have been used to make and alter specific food products like cheese, wine, single cell proteins, beer, and yogurt since before the term biotechnology was coined.
As prokaryotes have been used to make and alter specific food products like cheese, wine, bread, beer, and yogurt since before the term biotechnology was coined.
As prokaryotes have been used to alter specific food products like cheese, wine, bread, beer, and yogurt since before the term biotechnology was coined.

On what does the success of bioremediation of oil spills depend?

Success depends on the presence of only aromatic and highly branched hydrocarbon chain compounds and the temperature.
Success depends on the presence of less nonvolatile and more aromatic and highly branched hydrocarbon chain compounds and the temperature.
Success depends on the type of oil compounds, the presence of naturally occurring oil-solubilizing prokaryotes in the ocean, and the type of water body.
Success depends on the type of oil compounds, the presence of naturally occurring oil-solubilizing prokaryotes in the ocean and the temperature.

Why is the relationship between sustainable agriculture and nitrogen fixers called a mutualism?

Due to agrobacterium, which are nitrogen fixers, plants benefit from an endless supply of nitrogen; soils benefit from being naturally fertilized; and bacteria benefit from using photosynthates from plants.
Due to rhizobia, which are nitrogen fixers, plants benefit from an endless supply of nitrogen; soils benefit from being naturally fertilized; and bacteria benefit from using photosynthates from plants.
Due to rhizobia, which are nitrogen fixers, plants benefit from an endless supply of nitrogen; soils benefit from being naturally fertilized; and bacteria benefit from using potassium from plants.
Due to rhizobia, which are nitrogen fixers, plants benefit from a limited supply of nitrogen; soils benefit from being naturally fertilized; and bacteria benefit from using potassium from plants.

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Critical Thinking Questions

Phototrophic organisms appeared during the first two billion years of Earth’s existence. Anaerobic organisms appeared within one billion years of Earth’s formation. From these organisms evolved the cyanobacteria, which produce oxygen as a by-product of photosynthesis, leading to the oxygenation of the atmosphere.
For the first two billion years of Earth’s existence, the atmosphere had no molecular oxygen. Thus, the first organisms were anaerobic. Cyanobacteria appeared within one billion years of Earth’s formation. From these evolved the phototrophic organisms, which produce oxygen as a by-product of photosynthesis, leading to the oxygenation of the atmosphere.
For the first two billion years of Earth’s existence, the atmosphere had no molecular oxygen. Thus, the first organisms were anaerobic. Phototrophic organisms appeared within one billion years of Earth’s formation. From these organisms evolved the cyanobacteria, which produce oxygen as a by-product of photosynthesis, leading to the oxygenation of the atmosphere.
For the first two billion years of Earth’s existence, the atmosphere had no molecular oxygen. Thus, the first organisms were anaerobic. Within one billion years of Earth's formation, cyanobacteria appeared, which produce oxygen as a by-product of photosynthesis, leading to the oxygenation of the atmosphere. From these organisms evolved phototrophic organisms.
Extremophiles can be altered genetically in vitro to allow them to live in extreme conditions and this capability of alteration can be used to help humans. For example, some water-resistant prokaryotes have developed DNA repair mechanisms. Also, they could be developed and used in the treatment of human disease.
Extremophiles have specialized adaptations that allow them to live in extreme conditions. These adaptations can be mobilized to help humans. For example, some water-resistant prokaryotes have developed DNA repair mechanisms. Also, they could be developed and used in the treatment of human disease.
Extremophiles can be altered genetically in vitro to allow them to live in extreme conditions and this capability of alteration can be used to help humans. For example, some radiation-resistant prokaryotes have developed DNA repair mechanisms. Also, they could be developed and used in the treatment of human disease.
Extremophiles have specialized adaptations that allow them to live in extreme conditions. These adaptations can be mobilized to help humans. For example, some radiation-resistant prokaryotes have developed DNA repair mechanisms. Also, they could be developed and used in the treatment of human disease.
Recombinant DNA techniques are used to detect the presence of a non-culturable prokaryote in an environmental sample. Polymerase chain reaction is used to amplify selected portions of prokaryotic DNA.
Molecular biology techniques are used to detect the presence of a non-culturable prokaryote in an environmental sample. Electrophoresis is used to amplify selected portions of prokaryotic DNA.
Molecular biology techniques are used to detect the presence of a non-culturable prokaryote in an environmental sample. Polymerase chain reaction is used to amplify selected portions of prokaryotic DNA.
Recombinant DNA techniques are used to detect the presence of a non-culturable prokaryote in an environmental sample. Electrophoresis is used to amplify selected portions of prokaryotic DNA.
Earth’s early environment was full of extreme places with high levels of oxygen in the atmosphere, no ozone to shield Earth’s surface from mutagenic radiation, much geologic upheaval, and volcanic activity. Extremophiles are bacteria and archaea that are adapted to grow in extreme environments.
Earth’s early environment was full of extreme places with little oxygen in the atmosphere, no ozone to shield Earth’s surface from mutagenic radiation, much geologic upheaval and volcanic activity. Extremophiles are bacteria and archaea that are adapted to grow in extreme environments.
Earth’s early environment was full of extreme places with little oxygen in the atmosphere and excessive concentrations of ozone that contributed to mutagenic radiation. Extremophiles are phototrophic bacteria and cyanobacteria that are adapted to grow in extreme environments.
For the first two billion years of Earth’s existence, the atmosphere had no molecular oxygen.
It has a cell wall enclosing cell membrane, cytoplasm, ribosomes and nucleoid region with genetic material. It may have a protective capsule, flagellum, pili and plasmids.
It has a cell wall enclosing cell membrane, cytoplasm, ribosomes and nucleus containing genetic material. It may have a protective capsule, flagellum, pili and plasmids.
It has a cell wall enclosing nuclear membrane, cytoplasm, ribosomes and nucleoid region with genetic material. It may have a protective capsule, flagellum, pili and plasmids.
It has a cell wall enclosing nuclear membrane, cytoplasm, mitochondria, vacuoles and nucleoid region with genetic material. It may have a protective capsule, flagellum, pili and plasmids.
Typical cells in Archaea and Bacteria contain a cell wall, cell membrane, nucleoid region, ribosomes, and often a capsule, flagellum, and pili. However, these are sometimes made from different chemical compounds. Cell walls of Bacteria contain peptidoglycan while Archaea do not. Plasma membrane lipids of Bacteria are fatty acids while those of Archaea are phytanyl groups.
Typical cells in Archaea and Bacteria contain a cell wall, cell membrane, nucleoid region and often a capsule, flagellum, and pili but in some instances different chemical compounds make them. Cell walls of Bacteria contain peptidoglycan while Archaea do not. Bacteria contain 70S ribosomes while Archaea contain 80S ribosomes.
Typical cells in Archaea and Bacteria contain a cell wall, nuclear membranes, nucleoid region and often a capsule, flagellum, and pili but in some instances different chemical compounds make them. Cell walls of Bacteria contain peptidoglycan while Archaea do not. Plasma membrane lipids of bacteria are fatty acids, while the plasma membrane lipids of Archaea are phytanyl groups.
Typical cells in Archaea and Bacteria contain a cell wall, cell membrane, nucleoid region and often a capsule, flagellum, and pili but in some instances different chemical compounds make them. Cell walls of Bacteria contain peptidoglycan while Archaea do not. Plasma membrane lipids of Bacteria are phytanyl groups, while the plasma membrane lipids of Archaea are fatty acids.
These three prokaryote groups have similar basic structural features. They typically have cell walls enclosing nuclear membranes, cytoplasm, ribosomes, mitochondria, and a nucleoid region with genetic material. They may have a protective capsule, flagellum, pili, and plasmids.
Cocci and spirilli have similar basic structural features. They typically have cell walls enclosing cell membranes, a flagellum for locomotion, and pili for attachment. Bacilli are rod shaped and contain ribosomes and a nucleoid region with genetic material.
These three prokaryote groups have similar basic structural features. They typically have cell walls enclosing cell membranes, cytoplasm, ribosomes, and a nucleoid region with chromosomes. They may have a protective capsule, flagellum, pili, and plasmids.
Bacilli and spirilli have similar basic structural features. They typically have cell walls enclosing nuclear membranes, a flagellum for locomotion, and pili for attachment. Cocci are spherical and contain ribosomes and a nucleoid region with genetic material.
Carbon, because it represents 12% of the total dry weight of a typical cell and is a component of all macromolecules.
Oxygen, because it is necessary and is a major component for all macromolecules. It also accounts for 50% of the total composition of a cell.
Carbon, because it is necessary and is a major component for all macromolecules. It also accounts for 50% of the total composition of a cell.
Nitrogen, because it is necessary and is a major component for all macromolecules. It also accounts for 50% of the total composition of a cell.
Chemoheterotroph, as it must rely on chemical sources of energy living in a lightless environment and a heterotroph if it uses organic compounds for its carbon source.
Chemoorganotroph, as it must rely on chemical sources of energy living in a lightless environment and an organotroph if it uses organic compounds for its carbon source.
Chemolitoautotroph, as it must rely on chemical sources of energy living in a lightless environment and an autotroph if it uses organic compounds for its carbon source.
My diet might include fruits or vegetables and water as nitrogen is present in the highest amount in water.
My diet might include fruits or vegetables, water and air as atmospheric nitrogen could be simply absorbed.
My diet might include fruits or vegetables, cheese, meat, water, and air as atmospheric nitrogen could be simply absorbed.
My diet might include cheese or meat, water, and air as atmospheric nitrogen could be simply absorbed.
Neither are important, as cells can survive as well as carry out essential functions without either types of nutrients.
Micronutrients, even though they are required in lesser amounts; without them cells cannot survive and carry out functional processes.
Macronutrients, as they are required in larger amounts by cells and thus are more essential than micronutrients.
Neither is more important as both types of nutrients are absolutely necessary for prokaryotic cell structure and function.

Botulism is a potentially fatal food-borne disease. It is caused by toxins from the bacteria Clostridium botulinum ( C. botulinum ). This bacteria produces spores, which are difficult to destroy. The graph shows the amount of time a sample needs to be heated based on temperature. Note the time scale is a log scale: Log 1 is 10 minutes, log 2 is 100 minutes and log 3 is 1,000 minutes.

Which treatment would effectively kill the spores and be safe?

Heating for 120 minutes at 70 °C.
Heating for 100 minutes at 75 °C.
Heating for 300 minutes at 85°C.
Heating for 30 minutes at 90°C.
Yes, better sterilization and canning procedures have reduced the incidence of botulism. Most cases of foodborne illness now are related to small-scale food production.
No, better sterilization and canning procedures have reduced the incidence of botulism. Most cases of foodborne illness now are related to small-scale food production.
No, better sterilization and canning procedures have increased the incidence of botulism. Most cases of foodborne illnesses now are related to large-scale food production.
Yes, better sterilization and canning procedures have reduced the incidence of botulism. Most cases of foodborne illnesses now are related to large-scale food production.

Botulism is a potentially fatal food-borne disease. It is caused by toxins from the bacteria Clostridium botulinum ( C. botulinum ). This bacteria produces spores, which are difficult to destroy. The graph shows how heating affects C. botulinum spores. The spores are heated to 75°C and kept at that temperature.

Make a claim based on this graph.

Heating to 75°C kill C. botulinum spores almost instantly.
Keeping the spores at 75°C for 10 minutes kills most of the spores.
For most spores to die, the 75°C temperature must be kept for more than two hours.
Heating to 75°C has very little effect on C. botulinum spores.
The Plague of Athens was a disease believed caused by Yersinia pestis that killed one-quarter of Athenian troops in 430 BC. The bacterium causes between 10 and 15 million cases of typhoid fever today, resulting in over 10,000 deaths annually.
The Plague of Athens was a disease believed caused by Salmonella entericaserovar typhi that killed one-quarter of Athenian troops in 430 BC. The bacterium causes between 5 and 10 million cases of typhoid fever today, resulting in over 20,000 deaths annually.
The Plague of Athens was a disease believed caused by Yersinia pestis that killed one-quarter of Athenian troops in 430 BC. The bacterium causes between 16 and 33 million cases of typhoid fever today, resulting in over 200,000 deaths annually.
The Plague of Athens was a disease believed caused by Salmonella entericaserovar typhi that killed one-quarter of Athenian troops in 430 BC. The bacterium causes between 16 and 33 million cases of typhoid fever today, resulting in over 200,000 deaths annually.
Plants benefit from an endless supply of nitrogen; soils benefit from being naturally fertilized; and bacteria benefit from using potassium from plants.
Plants benefit from a limited supply of nitrogen; soils benefit from being naturally fertilized, and bacteria benefit from using photosynthates from plants.
Plants benefit from an endless supply of carbon; soils benefit from being naturally fertilized; and bacteria benefit from using photosynthates from plants.
Plants benefit from an endless supply of nitrogen; soils benefit from being naturally fertilized; and bacteria benefit from using photosynthates from plants.

The image shows the results of a research that studied various bacteria for their ability to remove mercury, cadmium and lead from an environment over time.

Make a claim about removal of mercury by these bacteria?

All the bacteria shown here can remove mercury from the environment.
The bacteria that remove the mercury complete the process in 3-4 days.
The bacteria that remove the mercury complete the process in 7-8 days.
Only a few bacteria shown here can remove the mercury from the environment.
Success depends on the presence of only aromatic and highly branched hydrocarbon chain compounds, and the temperature.
Success depends on the presence of less nonvolatile and more aromatic and highly branched hydrocarbon chain compounds, and the temperature.
Success depends on the type of oil compounds, the presence of naturally-occurring oil-solubilizing prokaryotes in the ocean, and the type of water body.
Success depends on the type of oil compounds, the presence of naturally-occurring oil-solubilizing prokaryotes in the ocean, and the temperature.
Due to agrobacterium which are nitrogen fixers, plants benefit from an endless supply of nitrogen; soils benefit from being naturally fertilized and bacteria benefit from using photosynthates from plants.
Due to rhizobia, which are nitrogen fixers, plants benefit from an endless supply of nitrogen; soils benefit from being naturally fertilized and bacteria benefit from using photosynthates from plants.
Due to rhizobia, which are nitrogen fixers, plants benefit from an endless supply of nitrogen; soils benefit from being naturally fertilized and bacteria benefit from using potassium from plants.
Due to rhizobia, which are nitrogen fixers, plants benefit from a limited supply of nitrogen; soils benefit from being naturally fertilized and bacteria benefit from using potassium from plants.

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Chapter 9: Earthquakes

Seismic Waves, Hazards, and their Distribution

Learning Objectives

The goals of this chapter are to:

Understand earthquakes and their associated hazards
Use seismic waves to locate earthquakes
Evaluate earthquakes related to induced seismicity

9.1 What are Earthquakes?

An earthquake is the shaking caused by breaking and movement of rocks beneath Earth’s surface. Why does the Earth move? When it is under stress, it deforms, then breaks and two sides slide past each other. Because most rock is strong (unlike loose sand), it can withstand a significant amount of stress without breaking. But every rock will rupture (break) once that limit is reached. For the case of rocks within the Earth, the rock breaks at depth and there is displacement along the rupture surface. This release of built-up elastic energy radiates away as seismic waves. The magnitude of the earthquake depends on the extent of the area that breaks (the area of the rupture surface) and the average amount of displacement (sliding).

In Chapter 2 you discovered that earthquakes occur near plate boundaries. Both divergent and transform boundaries have shallow earthquakes, whereas subduction zones can have deep earthquakes. But not all earthquakes occur along plate boundaries (Figure 9.1).

Exercise 9.1 – Observing Earthquake Hazard

Earthquakes pose a significant risk to the destruction of infrastructure and buildings and loss of life. Figure 9.1 is an earthquake hazard map of the U.S. Answer the questions below.

Map of seismic hazards for the United States

Explain what the colors on Figure 9.1 mean.
Which parts of the U.S. have a high earthquake hazard?
Which parts of the U.S. have a low earthquake hazard?
Why are earthquake hazards high on the west coast of the U.S.?
Do any locations of high earthquake-shaking hazards not correspond to any plate boundaries? Can you come up with an explanation for these areas?
Critical Thinking: Will places on the map that have the same color have the same level of damage if an earthquake occurs?

Exercise 9.2 – Comparing Earthquakes at Divergent Plate Boundaries

Divergent plate boundaries occur in both oceanic and continental crust. In oceanic plate boundaries (mid-ocean ridges), numerous transform faults offset these ridges. The location of earthquakes along these divergent boundaries is controlled by whether or not the divergent boundary and/or transform breaks due to brittle deformation. The brittle behavior of rocks is partly a function of temperature and pressure. Typically, only shallow and cool rocks will break. So, you can look at the patterns of earthquakes to determine if a mid-ocean ridge is hot or cool. Why is this important? Well, life and mineral resources are both sensitive to the thermal conditions at ridge crests.

Continental
For images A-C, are most earthquakes located on the spreading ridges, transforms, or both? Also, note if there are earthquakes located off the spreading ridge. Describe where the earthquakes are in images A-C.
Is there a relationship between the spreading rate and earthquake distribution? Discuss this as a class to explain what you observe.
An important feature of mid-ocean ridges is black smokers (hydrothermal vents). These form near or on spreading ridges in response to the thermal structure of a ridge, sea water interaction, and fracturing. They are sites for both mineral deposition and deep sea life. Which of these spreading ridges would you predict to have more black smokers? Why?
Look at the distribution of earthquakes and volcanos in the East African rift zone. Do these occur in the same region? Explain your observations.
Continental rifts occur in thick continental crust that is hard to break. Would you predict that there would be deeper earthquakes in continental rift zones? Do your observations support or disprove your hypothesis?
Critical Thinking: The East African rift valley is home to most of the African large mammals as well as where hominid evolution began. What features of this rift are important for biologic and evolutionary activity?

Four images of earthquake locations on divergent spreading centers

9.2 Seismic Waves

As you can imagine, technology does not exist to travel into all of Earth’s layers. Geoscientists learn a great deal about Earth’s structure through seismic waves. Seismic waves are vibrations in the Earth that transmit energy and occur during earthquakes, volcanic eruptions, and even man-made explosions and nuclear blasts.

Exercise 9.3 – Analogs for Seismic Wave Motion

When an earthquake occurs, seismic waves are released outward from the hypocenter (the location inside the Earth where the earthquake occurred). These waves have different characteristics, including their motion and velocity.

Using a slinky (can be either metal or plastic), hold one end and have a partner hold the other. Stretch the slinky to at least 8″. If you have a super slinky, you can go even further. Quickly push the slinky forward on your end and immediately pull back. Describe what happens.
With the same setup, quickly move your end of the slinky up, down, and back to the middle. Describe what you see.
Discuss with your instructor what these models represent.
If you shorten or lengthen the slinky, what is the result?
Does it make a difference if the slinky is metal or plastic? Why? ___________________
Seismologists like to know the relationship between wavelength, frequency and amplitude of waves. Set up an experiment to demonstrate these with your slinky or with several slinkies.

You can picture seismic waves moving through the Earth as circular waves similar to what happens when a stone is thrown into a pond, but more complex. Seismic waves can be distinguished by a number of properties including the speed the waves travel, the direction that the waves move particles as they pass by, and where they don’t propagate. In the previous exercise with a slinky, could you measure the wave speed? Typical seismic wave speeds are 330 m/s in air, 1450 m/s in water and about 5000 m/s in granite. The precise speed that a seismic wave travels through the Earth depends on several factors, most important is the composition of the rock.

Exercise 9.4 – Seismic Wave Velocity

When an earthquake occurs, seismic waves are released outward from the hypocenter (the location inside the earth where the earthquake occurred). These waves have different characteristics, including their motion and velocity.

Imagine two cars on a highway are driving right next to each other. Car 1 is traveling at 60 mph, and Car 2 is traveling at 70 mph. Both will maintain their speed. How far apart are the cars after 1 hour? ____________________
After 2 hours? ____________________
After 5 hours? ____________________
How many hours must pass for the cars to be 100 miles apart? ____________________
If the time is 5:30 p.m. and the cars are 75 miles apart, at what time did they start moving? ____________________
Seismic waves work the same way. P-waves and S-waves travel at different velocities away from the earthquake focus (Figure 9.3). Which wave travels faster? ____________________
How long does it take a P-wave to travel 1,000 km? ____________________
How long does it take an S-wave to travel 1,000 km? ____________________
You can use the difference in travel time to determine how far away an earthquake occurred. If the travel time difference between a P-wave and S-wave is 1 minute, how far away was the earthquake? ____________________
Critical Thinking: Does this tell you the exact location of the earthquake? Why or why not?

Graph of seismic wave travel time versus distance

The measurement for how powerful an earthquake is is called its magnitude. The magnitude can vary from place to place based on distance, type of surface material, and other factors. You may have heard about the Richter scale (M R ) for measuring magnitude, which is based on the amplitude of the seismic waves, but in practice it’s not commonly used anymore. The Moment Magnitude (M W ) is more accurate, especially with more power earthquakes. It’s based on the strength of the rock along the fault, the area of the fault that slipped, and the distance the fault moved. Thus, stronger rock material, or a larger area, or more movement in an earthquake will all contribute to produce a larger magnitude.

9.3 Locating Earthquakes

Since earthquakes all over the world, how do we determine where they occur? Sometimes they occur in the middle of the ocean or in remote areas where no one lives. Is this like the age old question that if a tree falls in the woods, does it make a sound? Even if there’s no person or other animal around to hear the tree falling and crashing, a recorder with a microphone could certainly record those vibrations—as sound. The same is true for earthquakes. Geoscientists have set up earthquake monitoring stations using seismometers around the world to record earthquake waves. These are set-up on global, national and regional scales. For example, the San Francisco Bay region has over 550 local monitoring stations while the Global Seismographic Network only has 152.

Do you want to set up your own earthquake monitoring station? You can with your smart phone as these have motion sensors to determine whether your phone is stationary or falling out of your hand. These include Seismograph, iSeismo, and VibrationMeter. In addition, there are now apps to help alert you if you live in an earthquake prone area, such as MyShake and Earthquake.

Exercise 9.5 – Locating an Earthquake

The location of earthquakes can be found by triangulating the origin of seismic waves. Figures 9.4 – 9.6 contain three-component seismograms for three different locations. The three components represent different directions of motion: Up-Down (vertical), North-South, and East-West.

On Figures, mark the arrival of the first P waves, S waves, and surface waves.

Table 9.1 – Seismic wave data to locate an earthquake
Seismic Station Location	P wave arrival time	S wave arrival time	S-P time (mm:ss)	Distance (km)
Tuscon, AZ
Corvallis, OR
Cathedral Caves, MO

Determine the amount of time between the arrival of P and S waves at each station. Record the time difference in Table 9.1.
Now that you know the difference in arrival times, you can tell how far away the earthquake was from each station. Use Figure 9.3 and find the chunk of time between the two curves. Record the distance in Table 9.1.
Head to the Iris triangulation webpage . Click “+ Station” and input the latitude and longitude of each station and the distance of the epicenter you determined. Look at the bottom of the page to edit this data. This will create a colored circle around each station that has a radius equal to the distance you entered. If you select this, show your instructor the map you made on the Iris webpage, then mark the earthquake’s epicenter on Figure 9.7.
Plot the three circles of your measured distance for each station using a compass on Figure 9.7. For both ways, where the three circles intersect (or come close to intersecting) is the location of the earthquake.
Is this earthquake located near a plate boundary? If so, what type of plate boundary is nearby?
How could you determine a more precise location?

Seismogram of an earthquake recorded in Tuscon, Arizona

This exercise is adapted from IRIS/SAGE .

9.4 Induced Seismicity

Induced seismicity is typically earthquakes and tremors that are caused by human activity that alters the stresses and strains on Earth’s crust. The first case of induced seismicity occurred in 1932 in Algeria’s Oued Fodda Dam. Most induced seismicity is of a low magnitude. Injecting fluid underground can induce earthquakes, a fact that was established decades ago. Injection increases the fluid pressure within the Earth, creating an area more likely to fail in an earthquake. When injected with fluids, even faults that have not moved in historical times can be made to slip and cause an earthquake.

Why inject fluid underground? Several reasons are wastewater disposal, hydraulic fracturing and enhanced oil recovery. Within the United States, each of these activities has induced earthquakes in the past few years. These are regulated under the Safe Drinking Water Act with standards set by the U.S. Environmental Protection Agency. Other purposes for injecting fluid underground include enhanced geothermal systems and geologic carbon sequestration.

Exercise 9.6 – Fracking and Earthquakes

Since 2001, oil and gas have been extracted from shale, but shale is not a permeable rock, so fluids can’t pass through it. Geologists can increase the permeability of shale so that oil and gas can flow and be extracted. This is done by hydraulic fracturing (“fracking”). During fracking, fluids are pumped into a well at high pressure to open and widen cracks in the shale, allowing the oil and gas to flow easier. This process causes small earthquakes (magnitudes smaller than 1), but large ones do occur with the largest induced earthquake being a M4 in Texas.

In addition, wastewater (a by-product of fracking) is frequently disposed of by injection into deep wells. The injection of wastewater into the subsurface can also cause earthquakes that are large enough to be damaging. Wastewater is injected deep underground, far below groundwater or drinking water aquifers. The largest earthquake known to be induced by wastewater disposal was a M5.8 earthquake that occurred near Pawnee, Oklahoma, in 2016.

Both fracking and wastewater disposal processes have affected Texas, Oklahoma, and New Mexico. Figure 9.8 shows the distribution of all earthquakes for two five-year periods 1997-2001 and 2019-2023, and Figure 9.8 shows the frequency of earthquake magnitude from 2019-2023.

Map of Texas and Oklahoma showing earthquake locations for 1997 to 2001 (orange circles) and 2019-2023 (green circles)

Use the 1997-2001 data from Figure 9.8 to determine the natural seismicity and where it occurred in this region. Do the earthquakes cluster in distinct areas? If so, where are these located?
Look at Texas in Figure 9.8, are the orange-colored earthquakes associated with any specific rocks? Open the interactive map of the geology of Texas and look at the regional trends and rock types; look to see what type of sedimentary rocks are there.
Use the 2019-2023 data from Figure 9.8 to understand where induced seismicity occurred in this region. Do the earthquakes cluster in distinct areas? If so, where are these located?
Do you think there are any natural earthquakes in in the 2019-2023 data?
Look at Texas in Figure 9.8, are the clusters of green-colored earthquakes associated with any specific rocks? Open the interactive map of the geology of Texas and look at the regional trends and rock types; look to see what type of sedimentary rocks are there.
Are these induced earthquakes hazardous? You can start to feel earthquakes with a magnitude of about 2.5, and you generally need above magnitude 4 to see damage, especially to poorly constructed buildings. Use Figure 9.9 to determine if there are any damaging earthquakes from 2019-2023.

9.5 Earthquake Hazards

Many movies and news reports depict death and destruction caused by earthquakes. Some of the natural hazards are landslides, fissures, avalanches, and tsunamis. Most of the hazards to people come from man-made structures themselves and the shaking they receive from the earthquake. The real dangers to people are being crushed in a collapsing building, drowning in a flood caused by a broken dam or levee, getting buried under a landslide, or being burned in a fire. In order to reduce risk in populated area as well as develop policies for land-use, insurance needs, and earthquake resistant design, knowledge of the types of hazards in any area need to be mapped. Some of these hazards are related to the types of rocks as well as how steep the terrain is. In the next exercise you will integrate information from a hazards map, geologic map as well as satellite image showing topography.

Exercise 9.7 – Earthquake Hazards

There are many other earthquake hazards besides the shaking from seismic waves. Liquefaction and landslides are two common hazards. Liquefaction occurs when loose, water-logged sediment loses its strength due to intense shaking from earthquakes, basically turning into quicksand. A landslide is a mass of earth or rock sliding down a mountain or cliff. Figure 9.10 is a map of the San Francisco Bay area in California that shows these hazards.

Natural hazard map for the San Francisco Bay region

What areas are prone to liquefaction?
What areas are prone to landslides?
Compare the Google Earth image (Figure 9.11) and the geologic map (Figure 9.12) to the hazards map (Figure 9.10). Describe some of the relationships between the type of hazard, geologic units, and topography for liquefaction and landslides.
Choose one of the bridges across San Francisco Bay and determine the geologic hazards associated with both sides of the bridge.
Your best friend is getting a job in San Ramon CA as a geologist in the headquarters of Chevron. She knows that earthquake hazards abound in CA. The hazard map, however, doesn’t indicate the hazards in this region located on the NE of Figure 9.10. Using the topography and geologic maps (Figures 9.11 and 9.12), let her know what the potential hazards are and where they occur around San Ramon CA.
1906 M7.9 San Francisco earthquake _________________________
1911 M6.0 Calaveras fault Morgan Hill earthquake ________________________
1980 M6.0 Livermore earthquake ________________________
1984 M6.3 Calaveras fault Morgan Hill earthquake ________________________
1989 M7.1 Loma Prieta earthquake__________________________
2001 M5.1 Napa earthquake ________________________
2007 M5.7 Calaveras fault ________________________

Additional Information

Exercise contributions.

Daniel Hauptvogel, Virginia Sisson, and Kaitlin Thomas

Investigating the Earth: Exercises for Physical Geology Copyright © 2024 by Daniel Hauptvogel, Virginia Sisson, and Michael Comas is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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News from the Columbia Climate School

The 12 Questions Earth Scientists Should Ask in the Next 10 Years

Earth Institute

“Geologic understanding of the earth has profound implications for people all across the globe,” said James A. Yoder, dean emeritus of Woods Hole Oceanographic Institution and chair of the committee that authored the report.

Some of the recommended questions go to enhancing our basic understanding of the planet, such as when and how plate tectonics developed; how geologic processes influence biodiversity; and how critical chemical elements are distributed and cycled. But all aim to advance understanding of how the earth impacts society. Other questions: What is an earthquake? What drives volcanism? What does the past reveal about the dynamics of the climate system? How is the Earth’s water cycle changing? How can earth science reduce the toll of geohazards?

The NSF’s Division of Earth Science (EAR) is the primary federal group for funding and providing essential infrastructure capabilities to the earth science community. The report recommends that EAR undertake initiatives to address gaps between existing and needed infrastructure. Several of these initiatives, such as funding a national consortium for geochronology, focus on supporting collaborative research. EAR should also fund facilities that provide new access to technical capabilities, such as a giant press to study rock and mineral behavior under pressure , and a near-surface geophysics center, says the report. These initiatives should not be developed at the expense of EAR’s core disciplinary research programs, and will require new funding, it says.

Highly trained STEM professionals will be central to future breakthroughs, but the field faces challenges in recruiting and retaining an inclusive workforce. The report recommends that EAR enhance its existing efforts to provide investment and centralized guidance to improve diversity and equity. EAR should also fund technical staff for grantees on a long-term basis, the authors say.

All the priority questions will require advances in high-performance computing, improved modeling capabilities, and enhanced data curation. EAR should initiate a standing committee to advise on cyber infrastructure needs, and implement a strategy to support data standards across the research community, the report says.

The authors say that joining with other federal agencies and NSF divisions, and international partners will allow for more efficient leveraging of facilities and infrastructure.

The study was undertaken by the Committee on Catalyzing Opportunities for Research in the Earth Sciences , comprised of scientists from 19 universities and scientific institutions. It was sponsored by the National Science Foundation.

Adapted from a press release by the National Academies of Sciences, Engineering, and Medicine.

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9 questions about climate change you were too embarrassed to ask

Basic answers to basic questions about global warming and the future climate.

by Brad Plumer , Umair Irfan , and Brian Resnick

This explainer was updated by Umair Irfan in December 2018 and draws heavily from a card stack written by Brad Plumer in 2015. Brian Resnick contributed the section on the Paris climate accord in 2017.

There’s a vast and growing gap between the urgency to fight climate change and the policies needed to combat it.

In 2018, the United Nations’ Intergovernmental Panel on Climate Change found that it is possible to limit global warming to 1.5 degrees Celsius this century, but the world may have as little as 12 years left to act. The US government’s National Climate Assessment , with input from NASA, the Environmental Protection Agency, and the Pentagon, also reported that the consequences of climate change are already here, ranging from nuisance flooding to the spread of mosquito-borne viruses into what were once colder climates. Left unchecked, warming will cost the US economy hundreds of billions of dollars.

However, these facts have failed to register with the Trump administration, which is actively pushing policies that will increase the emissions of heat-trapping gases.

Ever since he took office, President Donald Trump has rejected or undermined President Barack Obama’s signature climate achievements: the Paris climate agreement; the Clean Power Plan , the main domestic policy for limiting greenhouse gas emissions; and fuel economy standards , which target transportation, the largest US source of greenhouse gases.

At the same time, the Trump administration has aggressively boosted fossil fuels: opening unprecedented swaths of public lands to mining and drilling , attempting to bail out foundering coal power plants , and promoting hydrocarbon exploitation at climate change conferences .

Trump has also appointed climate change skeptics to key positions. Quietly, officials at these and other science agencies have been removing the words “climate change” from government websites and press releases.

Yet the evidence for humanity’s role in changing the climate continues to mount, and its consequences are increasingly difficult to ignore. Atmospheric carbon dioxide concentrations now top 408 parts per million, a threshold the planet hasn’t seen in millions of years . Greenhouse gas emissions reached a record high in 2018. Disasters worsened by climate change have taken hundreds of lives, destroyed thousands of homes, and cost billions of dollars.

The big questions now are how these ongoing changes in the climate will reverberate throughout the rest of the world, and what we should do about them. The answers bridge decades of research across geology, economics, and social science, which have been confounded by uncertainty and obscured by jargon. That’s why it can be a bit daunting to join the discussion for the first time, or to revisit the conversation after a hiatus.

To help, we’ve provided answers to some fundamental questions about climate change you may have been afraid to ask.

1) What is global warming?

In short: The world is getting hotter, and humans are responsible.

Yes, the planet’s temperature has changed before, but it’s the rise in average temperature of the Earth’s climate system since the late 19th century, the dawn of the Industrial Revolution, that’s important here. Temperatures over land and ocean have gone up 0.8° to 1° Celsius (1.4° to 1.8° Fahrenheit), on average, in that span:

Many people use the term “climate change” to describe this rise in temperatures and the associated effects on the Earth’s climate. (The shift from the term “global warming” to “climate change” was also part of a deliberate messaging effort by a Republican pollster to undermine support for environmental regulations.)

Like detectives solving a murder, climate scientists have found humanity’s fingerprints all over the planet’s warming, with the overwhelming majority of the evidence pointing to the extra greenhouse gases humans have put into the atmosphere by burning fossil fuels. Greenhouse gases like carbon dioxide trap heat at the Earth’s surface, preventing that heat from escaping back out into space too quickly. When we burn coal, natural gas, or oil for energy, or when we cut down forests that usually soak up greenhouse gases, we add even more carbon dioxide to the atmosphere, so the planet warms up.

Global warming also refers to what scientists think will happen in the future if humans keep adding greenhouse gases to the atmosphere.

Though there is a steady stream of new studies on climate change, one of the most robust aggregations of the science remains the Intergovernmental Panel on Climate Change’s fifth assessment report from 2013. The IPCC is convened by the United Nations, and the report draws on more than 800 expert authors. It projects that temperatures could rise at least 2°C (3.6°F) by the end of the century under many plausible scenarios — and possibly 4°C or more. A more recent study by scientists in the United Kingdom found a narrower range of expected temperatures if atmospheric carbon dioxide doubled, rising between 2.2°C and 3.4°C.

Many experts consider 2°C of warming to be unacceptably high , increasing the risk of deadly heat waves, droughts, flooding, and extinctions. Rising temperatures will drive up global sea levels as the world’s glaciers and ice sheets melt. Further global warming could affect everything from our ability to grow food to the spread of disease.

That’s why the IPCC put out another report in 2018 comparing 2°C of warming to a scenario with 1.5°C of warming . The researchers found that this half-degree difference is actually pretty important, since every bit of warming matters. Between the two outlooks, less warming means fewer people will have to move from coastal areas, natural weather events will be less severe, and economies will take a smaller hit.

However, limiting warming would likely require a complete overhaul of our energy system. Fossil fuels currently provide just over 80 percent of the world’s energy. To zero out emissions this century, we’d have to replace most of that with low-carbon sources like wind, solar, nuclear, geothermal, or carbon capture.

Beyond that, we may have to electrify everything that uses energy and start pulling greenhouse gases straight from the air. And to get on track for 1.5°C of warming, the world would have to halve greenhouse gas emissions from current levels by 2030.

That’s a staggering task, and there are huge technological and political hurdles standing in the way. As such, the world’s nations have been slow to act on global warming — many of the existing targets for curbing greenhouse gas emissions are too weak , yet many countries are falling short of even these modest goals.

2) How do we know global warming is real?

The simplest way is through temperature measurements. Agencies in the United States, Europe, and Japan have independently analyzed historical temperature data and reached the same conclusion: The Earth’s average surface temperature has risen roughly 0.8° Celsius (1.4° Fahrenheit) since the early 20th century.

But that’s not the only clue. Scientists have also noted that glaciers and ice sheets around the world are melting. Satellite observations since the 1970s have shown warming in the lower atmosphere. There’s more heat in the ocean, causing water to expand and sea levels to rise. Plants are flowering earlier in many parts of the world. There’s more humidity in the atmosphere. Here’s a summary from the National Oceanic and Atmospheric Administration:

These are all signs that the Earth really is getting warmer — and that it’s not just a glitch in the thermometers. That explains why climate scientists say things like , “Warming in the climate system is unequivocal.” They’re really confident about this one.

3) How do we know humans are causing global warming?

Climate scientists say they are more than 95 percent certain that human influence has been the dominant cause of global warming since 1950. They’re about as sure of this as they are that cigarette smoke causes cancer.

Why are they so confident? In part because they have a good grasp of how greenhouse gases can warm the planet, in part because the theory fits the available evidence, and in part because alternate theories have been ruled out. Let’s break it down in six steps:

1) Scientists have long known that greenhouse gases in the atmosphere — such as carbon dioxide, methane, or water vapor — absorb certain frequencies of infrared radiation and scatter them back toward the Earth. These gases essentially prevent heat from escaping too quickly back into space, trapping that radiation at the surface and keeping the planet warm.

2) Climate scientists also know that concentrations of greenhouse gases in the atmosphere have grown significantly since the Industrial Revolution. Carbon dioxide has risen 45 percent . Methane has risen more than 200 percent . Through some relatively straightforward chemistry and physics , scientists can trace these increases to human activities like burning oil, gas, and coal.

3) So it stands to reason that more greenhouse gases would lead to more heat. And indeed, satellite measurements have shown that less infrared radiation is escaping out into space over time and instead returning to the Earth’s surface. That’s strong evidence that the greenhouse effect is increasing.

4) There are other human fingerprints that suggest increased greenhouse gases are warming the planet. For instance, back in the 1960s, simple climate models predicted that global warming caused by more carbon dioxide would lead to cooling in the upper atmosphere (because the heat is getting trapped at the surface). Later satellite measurements confirmed exactly that . Here are a few other similar predictions that have also been confirmed.

5) Meanwhile, climate scientists have ruled out other explanations for the rise in average temperatures over the past century. To take one example: Solar activity can shift from year to year, affecting the Earth’s climate. But satellite data shows that total solar irradiance has declined slightly in the past 35 years, even as the Earth has warmed.

6) More recent calculations have shown that it’s impossible to explain the temperature rise we’ve seen in the past century without taking the increase in carbon dioxide and other greenhouse gases into account. Natural causes, like the sun or volcanoes, have an influence, but they’re not sufficient by themselves.

Ultimately, the Intergovernmental Panel on Climate Change concluded that most of the warming since 1951 has been due to human activities. The Earth’s climate can certainly fluctuate from year to year due to natural forces (including oscillations in the Pacific Ocean, such as El Niño ). But greenhouse gases are driving the larger upward trend in temperatures.

And as the Climate Science Special Report , released by 13 US federal agencies in November 2017, put it, “For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence.”

More: This chart breaks down all the different factors affecting the Earth’s average temperature. And there’s much more detail in the IPCC’s report , particularly this section and this one .

4) How has global warming affected the world so far?

Here’s a list of ongoing changes that climate scientists have concluded are likely linked to global warming, as detailed by the IPCC here and here .

Higher temperatures: Every continent has warmed substantially since the 1950s. There are more hot days and fewer cold days, on average, and the hot days are hotter.

Heavier storms and floods: The world’s atmosphere can hold more moisture as it warms. As a result, the overall number of heavier storms has increased since the mid-20th century, particularly in North America and Europe (though there’s plenty of regional variation). Scientists reported in December that at least 18 percent of Hurricane Harvey’s record-setting rainfall over Houston in August was due to climate change.

Heat waves: Heat waves have become longer and more frequent around the world over the past 50 years, particularly in Europe, Asia, and Australia.

Shrinking sea ice: The extent of sea ice in the Arctic, always at its maximum in winter, has shrunk since 1979, by 3.3 percent per decade. Summer sea ice has dwindled even more rapidly, by 13.2 percent per decade. Antarctica has seen recent years with record growth in sea ice, but it’s a very different environment than the Arctic, and the losses in the north far exceed any gains at the South Pole, so total global sea ice is on the decline:

Shrinking glaciers and ice sheets: Glaciers around the world have, on average, been losing ice since the 1970s. In some areas, that is reducing the amount of available freshwater. The ice sheet on Greenland, which would raise global sea levels by 25 feet if it all melted, is declining, with some sections experiencing a sudden surge in the melt rate. The Antarctic ice sheet is also getting smaller, but at a much slower rate .

Sea level rise: Global sea levels rose 9.8 inches (25 centimeters) in the 19th and 20th centuries, after 2,000 years of relatively little change , and the pace is speeding up . Sea level rise is caused by both the thermal expansion of the oceans — as water warms up, it expands — and the melting of glaciers and ice sheets (but not sea ice).

Food supply: A hotter climate can be both good for crops (it lengthens the growing season, and more carbon dioxide can increase photosynthesis) and bad for crops (excess heat can damage plants). The IPCC found that global warming was currently benefiting crops in some high-latitude areas but that negative effects are becoming increasingly common worldwide. In areas like California, crop yields are estimated to decline 40 percent by 2050.

Shifting species: Many land and marine species have had to shift their geographic ranges in response to warmer temperatures. So far, several extinctions have been linked to global warming, such as certain frog species in Central America.

Warmer winters: In general, winters are warming faster than summers . Average low temperatures are rising all over the world. In some cases, these temperatures are climbing above the freezing point of water. We’re already seeing massive declines in snow accumulation in the United States, which can paradoxically increase flood, drought, and wildfire risk — as water that would ordinarily dispatch slowly over the course of a season instead flows through a region all at once.

Debated impacts

Here are a few other ways the Earth’s climate has been changing — but scientists are still debating whether and how they’re linked to global warming:

Droughts have become more frequent and more intense in some parts of the world — such as the American Southwest, Mediterranean Europe, and West Africa — though it’s hard to identify a clear global trend. In other parts of the world, such as the Midwestern United States and Northwestern Australia, droughts appear to have become less frequent. A recent study shows that, globally, the time between droughts is shrinking and more areas are affected by drought and taking longer to recover from them.

Hurricanes have clearly become more intense in the North Atlantic Ocean since 1970, the IPCC says. But it’s less clear whether global warming is driving this. 2017 was an exceptionally bad year for Atlantic hurricanes in terms of strength and damage. And while scientists are still uncertain whether they were a fluke or part of a trend, they are warning we should treat it as a baseline year. There doesn’t yet seem to be any clear trajectory for tropical cyclones worldwide.

5) What impacts will global warming have in the future?

It depends on how much the planet actually heats up. The changes associated with 4° Celsius (or 7.2° Fahrenheit) of warming are expected to be more dramatic than the changes associated with 2°C of warming.

Here’s a basic rundown of big impacts we can expect if global warming continues, via the IPCC ( here and here ).

Hotter temperatures: If emissions keep rising unchecked, then global average surface temperatures will be at least 2°C higher (3.6°F) than preindustrial levels by 2100 — and possibly 3°C or 4°C or more.

Higher sea level rise: The expert consensus is that global sea levels will rise somewhere between 0.2 and 2 meters by the end of the century if global warming continues unchecked (that’s between 0.6 and 6.6 feet). That’s a wide range, reflecting some of the uncertainties scientists have in how ice will melt. In specific regions like the Eastern United States, sea level rise could be even higher, and around the world, the rate of rise is accelerating .

Heat waves: A hotter planet will mean more frequent and severe heat waves .

Droughts and floods: Across the globe, wet seasons are expected to become wetter, and dry seasons drier. As the IPCC puts it , the world will see “more intense downpours, leading to more floods, yet longer dry periods between rain events, leading to more drought.”

Hurricanes: It’s not yet clear what impact global warming will have on tropical cyclones. The IPCC said it was likely that tropical cyclones would get stronger as the oceans heat up, with faster winds and heavier rainfall. But the overall number of hurricanes in many regions was likely to “either decrease or remain essentially unchanged.”

Heavier storm surges: Higher sea levels will increase the risk of storm surges and flooding when storms do hit.

Agriculture: In many parts of the world, the mix of increased heat and drought is expected to make food production more difficult. The IPCC concluded that global warming of 1°C or more could start hurting crop yields for wheat, corn, and rice by the 2030s, especially in the tropics. (This wouldn’t be uniform, however; some crops may benefit from mild warming, such as winter wheat in the United States.)

Extinctions: As the world warms, many plant and animal species will need to shift habitats at a rapid rate to maintain their current conditions. Some species will be able to keep up; others likely won’t. The Great Barrier Reef, for instance, may not be able to recover from major recent bleaching events linked to climate change. The National Research Council has estimated that a mass extinction event “could conceivably occur before the year 2100.”

Long-term changes: Most of the projected changes above will occur in the 21st century. But temperatures will keep rising after that if greenhouse gas levels aren’t stabilized. That increases the risk of more drastic longer-term shifts. One example: If West Antarctica’s ice sheet started crumbling, that could push sea levels up significantly. The National Research Council in 2013 deemed many of these rapid climate surprises unlikely this century but a real possibility further into the future.

6) What happens if the world heats up more drastically — say, 4°C?

The risks of climate change would rise considerably if temperatures rose 4° Celsius (7.2° Fahrenheit) above preindustrial levels — something that’s possible if greenhouse gas emissions keep rising at their current rate.

The IPCC says 4°C of global warming could lead to “substantial species extinctions,” “large risks to global and regional food security,” and the risk of irreversibly destabilizing Greenland’s massive ice sheet.

One huge concern is food production: A growing number of studies suggest it would become significantly more difficult for the world to grow food with 3°C or 4°C of global warming. Countries like Bangladesh, Egypt, Vietnam, and parts of Africa could see large tracts of farmland turn unusable due to rising seas. Scientists are also concerned about crops getting less nutritious due to rising CO2.

Humans could struggle to adapt to these conditions. Many people might think the impacts of 4°C of warming will simply be twice as bad as those of 2°C. But as a 2013 World Bank report argued, that’s not necessarily true. Impacts may interact with each other in unpredictable ways. Current agriculture models, for instance, don’t have a good sense of what will happen to crops if increased heat waves, droughts, new pests and diseases, and other changes all start to combine.

“Given that uncertainty remains about the full nature and scale of impacts,” the World Bank report said, “there is also no certainty that adaptation to a 4°C world is possible.” Its conclusion was blunt: “The projected 4°C warming simply must not be allowed to occur.”

7) What do climate models say about the warming that could actually happen in the coming decades?

That depends on your faith in humanity.

Climate models depend on not only complicated physics but the intricacies of human behavior over the entire planet.

Generally, the more greenhouse gases humanity pumps into the atmosphere, the warmer it will get. But scientists aren’t certain how sensitive the global climate system is to increases in greenhouse gases. And just how much we might emit over the coming decades remains an open question, depending on advances in technology and international efforts to cut emissions.

The IPCC groups these scenarios into four categories of atmospheric greenhouse gas concentrations known as Representative Concentration Pathways . They serve as standard benchmarks for evaluating climate models, but they also have some assumptions baked in .

RCP 2.6, also called RCP 3PD, is the scenario with very low greenhouse gas concentrations in the atmosphere. It bets on declining oil use, a population of 9 billion by 2100, increasing energy efficiency, and emissions holding steady until 2020, at which point they’ll decline and even go negative by 2100. This is, to put it mildly, very optimistic.

The next tier up is RCP 4.5, which still banks on ambitious reductions in emissions but anticipates an inflection point in the emissions rate around 2040. RCP 6 expects emissions to increase 75 percent above today’s levels before peaking and declining around 2060 as the world continues to rely heavily on fossil fuels.

The highest tier, RCP 8.5, is the pessimistic business-as-usual scenario, anticipating no policy changes nor any technological advances. It expects a global population of 12 billion and triple the rate of carbon dioxide emissions compared to today by 2100.

Here’s how greenhouse gas emissions under each scenario stack up next to each other:

And here’s what that means for global average temperatures, assuming that a doubling of carbon dioxide concentrations in the atmosphere leads to 3°C of warming:

As you can see, RCP 3PD is the only trajectory that keeps the planet below 2°C of warming. Recall what it would take to keep emissions in line with this pathway and you’ll understand the enormity of the challenge of meeting this goal.

8) How do we stop global warming?

The world’s nations would need to cut their greenhouse gas emissions by a lot. And even that wouldn’t stop all global warming.

For example, let’s say we wanted to limit global warming to below 2°C. To do that, the IPCC has calculated that annual greenhouse gas emissions would need to drop at least 40 to 70 percent by midcentury.

Emissions would then have to keep falling until humans were hardly emitting any extra greenhouse gases by the end of the century. We’d also have to remove carbon dioxide from the atmosphere .

Cutting emissions that sharply is a daunting task. Right now, the world gets 87 percent of its primary energy from fossil fuels: oil, gas, and coal. By contrast, just 13 percent of the world’s primary energy is “low carbon”: a little bit of wind and solar power, some nuclear power plants, a bunch of hydroelectric dams. That’s one reason global emissions keep rising each year.

To stay below 2°C, that would all need to change radically. By 2050, the IPCC notes, the world would need to triple or even quadruple the share of clean energy it uses — and keep scaling it up thereafter. Second, we’d have to get dramatically more efficient at using energy in our homes, buildings, and cars. And stop cutting down forests. And reduce emissions from agriculture and from industrial processes like cement manufacturing.

The IPCC also notes that this task becomes even more difficult the longer we put it off, because carbon dioxide and other greenhouse gases will keep piling up in the atmosphere in the meantime, and the cuts necessary to stay below the 2°C limit become more severe.

9) What are we actually doing to fight climate change?

A global problem requires global action, but with climate change, there is a yawning gap between ambition and action.

The main international effort is the 2015 Paris climate accord, of which the United States is the only country in the world that wants out . The deal was hammered out over weeks of tense negotiations and weighs in at 31 pages . What it does is actually pretty simple.

The backbone is the global target of keeping global average temperatures from rising 2°C (compared to temperatures before the Industrial Revolution) by the end of the century. Beyond 2 degrees, we risk dramatically higher seas, changes in weather patterns, food and water crises, and an overall more hostile world.

Critics have argued that the 2-degree mark is arbitrary, or even too low , to make a difference. But it’s a starting point, a goal that, before Paris, the world was on track to wildly miss.

Paris is voluntary

To accomplish this 2-degree goal, the accord states that countries should strive to reach peak emissions “as soon as possible.” (Currently, we’re on track to hit peak emissions around 2030 or later , which will likely be too late.)

But the agreement doesn’t detail exactly how these countries should do that. Instead, it provides a framework for getting momentum going on greenhouse gas reduction, with some oversight and accountability. For the US, the pledge involves 26 to 28 percent reductions by 2025. (Under Trump’s current policies, that goal is impossible .)

There’s also no defined punishment for breaking it. The idea is to create a culture of accountability (and maybe some peer pressure) to get countries to step up their climate game.

In 2020, delegates are supposed to reconvene and provide updates about their emission pledges and report on how they’re becoming more aggressive on accomplishing the 2-degree goal.

However, many countries are already falling behind on their climate change commitments, and some, like Germany, are giving up on their near-term targets.

Paris asks richer countries to help out poorer countries

There’s a fundamental inequality when it comes to global emissions. Rich countries have plundered and burned huge amounts of fossil fuels and gotten rich from them. Poor countries seeking to grow their economies are now being admonished for using the same fuels. Many low-lying poor countries also will be among the first to bear the worst impacts of climate change.

The main vehicle for rectifying this is the Green Climate Fund , via which richer countries, like the US, are supposed to send $100 billion a year in aid and financing by 2020 to the poorer countries. The United States’ share was $3 billion , but with President Trump’s decision to withdraw from the Paris accord, this goal is unlikely to be met.

The agreement matters because we absolutely need momentum on this issue

The Paris agreement is largely symbolic, and it will live on even though Trump is aiming to pull the US out. But, as Jim Tankersley wrote for Vox , “the accord will be weakened, and, much more importantly, so will the fragile international coalition” around climate change.

We’re already seeing the Paris agreement lose steam. At a follow-up climate meeting this year in Katowice, Poland , negotiators forged an agreement on measuring and verifying their progress in cutting greenhouse gases, but left many critical questions of how to achieve these reductions unanswered.

But the Paris accord isn’t the only international climate policy game in town

There are regional international climate efforts like the European Union’s Emissions Trading System . However, the most effective global policy at keeping warming in check to date doesn’t have to do with climate change, at least on the surface.

The 1987 Montreal Protocol , which was convened by countries to halt the destruction of the ozone layer, had a major side effect of averting warming. In fact, it’s been the single most effective effort humanity has undertaken to fight climate change. Since many of the substances that eat away at the ozone layer are potent heat-trappers, limiting emissions of gases like chlorofluorocarbons has an outsize effect.

And the Trump administration doesn’t appear as hostile to Montreal as it does to Paris. The White House may send the 2016 Kigali Amendment to the Montreal Protocol to the Senate for ratification, giving the new regulations the force of law. If implemented, the amendment would avert 0.5°C of warming by 2100.

Regardless of what path we choose, the key thing to remember is that we are going to pay for climate change one way or another. We have the opportunity now to address warming on our own terms, with investments in clean energy, moving people away from disaster-prone areas, and regulating greenhouse gas emissions. Otherwise, we’ll pay through diminished crop harvests, inundated coastlines, destroyed homes, lost lives, and an increasingly unlivable planet. Ignoring or stalling on climate change chooses the latter option by default. Our choices do matter, but we’re running out of time to make them.

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Effective Critical-Thinking Questions to Use in Class

Jessica shaffer.

May 17, 2021

Teacher calling on students with their hands up in a classroom.

What is Critical Thinking?

Critical thinking does not have just one definition, but one way to explain it is that it is “thinking about one’s thinking.” A critical thinker does not always take things at face value and will question ideas to further understand them. Critical thinkers also have the ability to see past the surface of something, and they possess important skills such as the ability to analyze, interpret, make inferences, and problem-solve. Critical thinkers also tend to be inquisitive about many issues, have a concern to remain well-informed, and embrace and even seek out critical thinking opportunities. Simply stated, critical thinkers think deep thoughts.

What is the Importance of Critical Thinking for Students?

Back in the day, school was different! Honestly, even a year ago, school was far different than it is now, but there is currently so much more emphasis on the “why” and the “how” than just knowing what the answer is. Critical thinking skills are important for students because of the curricula they are exposed to. “Right there” questions are few and far between and students have to rely on their own ability to dig deeper and read between the lines. There is a lot of emphasis placed on college and career readiness, and part of that is to prepare students to problem solve when there is no apparent answer.

Critical thinking provides students opportunities to acquire the higher-level thinking skills that will be needed for career and beyond. It is important to teach students at a young age that you cannot find the answer to everything in a book or through Google. You have to look within yourself to find many answers and, most importantly, justify why that is your answer. There are many ways teachers can incorporate these types of questions throughout the day, you just have to change your mindset a bit!

Critical Thinking Questions to Use in Class

A teacher will ask questions that usually contain one of the following components: who, what, where, when, how, or why. Using good questioning techniques is important and not always as difficult as it seems. Just changing the way that you start a question can change the way students think about an answer or solution. For example, instead of asking students “Who stole the pizza?”, ask students, “Why would that character want to steal the pizza?”

A critical thinking question should aim to make you think. It should lead students to ponder the answer and discuss possible solutions. Critical thinking questions can even lead to disagreements and arguments that can turn into an impressive teachable moment.

One way to incorporate a solid critical thinking question into a math lesson is to have the students solve a problem, and then ask students how they solved the problem. You can have the students talk it out or have each student write down a written explanation and then share it out. Either of these techniques gives various perspectives on how to solve the same problems and can help students to develop math sense.

Another way to incorporate critical thinking questions into math is to present a problem that is solved incorrectly and have students analyze the mistake. Students will have to solve for the correct answer and determine where the mistake occurred. To make this even more challenging, present a word problem or a multi-step story problem to further present critical thinking challenges.

Making inferences is generally one of the most difficult skills for students to learn. This is where students must use their critical thinking skills to understand what is not written or observed. Students must use evidence and couple it with reasoning skills to form a conclusion. A basic example would be looking at a photograph of a dog holding a leash in its mouth and coming to the conclusion that the dog would like to go for a walk.

Morning journals for students can present the perfect opportunity to enhance critical thinking skills. Instead of asking basic questions with basic answers, create questions that force students to think outside the box. For example, ask the question, “Is creativity something that can be measured? Should it be?” Instead of asking what creativity is and giving an example, this question makes a student pause and think about the answer before beginning to respond. These are the types of questions that can frustrate students “in a good way.”

A great way to encourage critical thinking in ELA is to ask students to write an alternate ending to a story. This promotes creativity and deep thinking. Then, students can explain how changing the ending of the story could have an impact on not just the novel, but the world. Encouraging students to think on a more global level also encourages a higher-level of thinking as well as a better understanding of the culture of the world, not just the small bubble they reside in.

Science is a subject perfect for inquiry! Having students think as an engineer would is a critical thinking skill at it’s finest. Students have to design a solution, test it, and then design an even better solution in order to combat weaknesses in the original design. This can be applied at any grade level.

A terrific way to incorporate critical thinking in Social Studies is similar to ELA by changing the outcome of important events in history. For example, have students discuss how our lives would be different if the Civil War had been won by the South. How would it have changed subsequent events in our history and what would life be like today? The opportunities are endless.

Ending Thoughts

All in all, teachers can create many opportunities each and every day for students to use critical thinking skills. It is as simple as starting the day off with a critical thinking question and changing certain techniques. Even if you ask the students a basic question, follow it up with something that requires more depth of thought. As the great Albert Einstein once said, “Education is not the learning of facts, but the training of the mind to think.” Force students to think about their thinking, and get them ready for the real world!

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Critical Thinking Questions

Chapter 9: Earthquakes

Learning Objectives

9.1 What are Earthquakes?

Exercise 9.1 – Observing Earthquake Hazard

Exercise 9.2 – Comparing Earthquakes at Divergent Plate Boundaries

9.2 Seismic Waves

Exercise 9.3 – Analogs for Seismic Wave Motion

Exercise 9.4 – Seismic Wave Velocity

9.3 Locating Earthquakes

Exercise 9.5 – Locating an Earthquake

9.4 Induced Seismicity

Exercise 9.6 – Fracking and Earthquakes

9.5 Earthquake Hazards

Exercise 9.7 – Earthquake Hazards

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9 questions about climate change you were too embarrassed to ask

1) What is global warming?

2) How do we know global warming is real?

3) How do we know humans are causing global warming?

4) How has global warming affected the world so far?

Debated impacts

5) What impacts will global warming have in the future?

6) What happens if the world heats up more drastically — say, 4°C?

7) What do climate models say about the warming that could actually happen in the coming decades?

8) How do we stop global warming?

9) What are we actually doing to fight climate change?

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K-12 Resources By Teachers, For Teachers Provided by the K-12 Teachers Alliance

Effective Critical-Thinking Questions to Use in Class

What is Critical Thinking?

What is the Importance of Critical Thinking for Students?

Critical Thinking Questions to Use in Class

Ending Thoughts

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