AP Enviormental Unit 4 Study Guide

Unit 4: Earth’s Systems and Resources

Unit 4 Exam Study Guide

4.1 Tectonic Plates

Convergent Boundaries

At a convergent boundary, two tectonic plates are moving towards each other ( -> <- ). Typically, at these boundaries, subduction takes place as the tectonic plate that is more dense moves under the plate that is less dense. An example of a convergent boundary is the Mariana Trench.

These converging plates can be between two oceanic plates or a continental and oceanic plate. Depending on the plates that are converging, different structures can form. Between oceanic plates, it is more likely for island arcs, oceanic trenches, and volcanoes to form. Between an oceanic plate and continental plate, it is likely for mountains and volcanoes to form.

Divergent Boundaries

At a divergent boundary, two tectonic plates are moving apart from each other ( <--> ). This can create visible fault lines, rift valleys, seafloor spreading, volcanoes, and earthquakes. A few examples of divergent boundaries are the East Africa Rift Valley, Mid-Atlantic Ridge, and the East Pacific Rise.

Seafloor spreading is a process that takes place at divergent boundaries on the ocean floor. As the two tectonic plates move apart from each other, magma is able to go up through the space between the plates. The cool ocean water cools it down and more rock forms.

Transform Boundaries

At a transform boundary, two tectonic plates slide past each other 🔼🔽. This often causes earthquakes. As the plates slide past each other, friction and energy build up. When this heat/energy is released quickly, an earthquake results. An example of a transform boundary is the San Andreas Fault in California.

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Plate Tectonics Map

By analyzing maps of tectonic plates and the landforms that occur there, geologists can better understand tectonic plate movements. For example, we can better understand the volcanoes and plate tectonics by looking at the Ring of Fire in the Pacific Ocean and the plate movements that cause it. We can also predict optimal ways for natural disaster prevention by understanding where and when a certain fault line event is possible.

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Key Terms to Review (7)

Convergent Boundary: A convergent boundary is where two tectonic plates collide or come together. This collision can result in various geological features such as mountains, volcanic activity, and earthquakes.

Divergent Boundary: A divergent boundary is where two tectonic plates move away from each other, resulting in the creation of new crust as magma rises to fill the gap.

Earthquakes: Earthquakes are sudden and violent shaking of the ground caused by the movement of tectonic plates. They occur when stress builds up along faults in the Earth's crust and is released in the form of seismic waves.

Rift Valleys: Rift valleys are long, narrow depressions on Earth's surface that form when tectonic plates move apart. They are characterized by steep walls and can be filled with water or contain fertile soils.

Subduction: Subduction is the process in which one tectonic plate moves beneath another plate at a convergent boundary, resulting in the recycling of old crust back into the Earth's mantle.

Transform Boundary: A transform boundary is a type of plate boundary where two tectonic plates slide past each other horizontally. This movement can cause earthquakes.

Volcanoes: Volcanoes are openings in the Earth's crust through which molten rock (magma), ash, gases, and other materials erupt onto its surface. They form due to plate tectonics or hotspots.

4.2 Soil Formation and Erosion

Soil formation is an important process in the environment that creates the ability of plants to grow. Through the formation of soil, different soil horizons are created that have different properties and nutrients. The soil itself is one of the most critical pieces of an environment so protecting it is crucial. 

Soil Formation

Soil formation starts with parent material. Over time, weathering occurs and the parent material is broken down into smaller and smaller particles. Also, particles from other places might be introduced through the deposition. 

Once a small layer of soil has been formed, moss and other small vegetation begin to grow. With the presence of small vegetation and organisms, more soil horizons form and nutrients are added to the soil. From here, the soil continues to develop as more plants and organisms interact with it.

Soil Horizons

| A Horizon (Topsoil) | Mixture of organic materials with minerals | | E Horizon (Eluviated) | Zone of Leaching, nutrients from upper horizons moves to lower horizons | | B Horizon (Subsoil) | Zone of Accumulation where minerals such as iron and other nutrients accumulate | | C Horizon (Parent Material) | The material that is broken down to create the soil | | Bedrock | Solid rock that lies beneath the parent material and soil |

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Soil Erosion and Water Quality

Due to soil’s importance to the environment, it is critical that it is protected. Often, soil can be washed away or eroded away by wind and water. This happens when no plants or vegetation are available to hold the soil in place. An example of this is the Dust Bowl that took place in the US.

Erosion can negatively impact water quality. One thing that soil does is filter water with the help of vegetation. No soil or vegetation means that water won’t be filtered which might result in unclean water with higher amounts of pollutants.

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Key Terms to Review (4)

C horizon: The C horizon is the layer of soil that consists of weathered parent material. It is located below the B horizon and above the unweathered bedrock.

Soil erosion: Soil erosion is the process by which soil is moved or displaced from one location to another, usually due to natural forces like wind and water. It can lead to the loss of fertile topsoil, making it difficult for plants to grow.

Soil Horizons: Soil horizons are distinct layers or zones within soil profiles that have different physical and chemical properties. These horizons form as a result of various processes such as weathering, organic matter accumulation, leaching, and mineral deposition.

Water Quality: Water quality refers to the chemical, physical, and biological characteristics of water, particularly in relation to its suitability for a specific purpose, such as drinking, recreation, or supporting aquatic life. Good water quality is crucial for maintaining ecosystems, human health, and overall environmental balance, while poor water quality can lead to serious ecological issues and public health concerns.

4.3 Soil Composition and Properties

Water-Holding Capacity and Retention

The water-holding capacity of the soil is the amount of water that soil can absorb given the effects of gravity upon the soil. Particle size and amount of organic matter present plays a big role in water-holding capacity. When talking about water retention in regards to farming, soil is desirable when it's able to keep water in its pores rather than allowing it to penetrate further and further into the crust.

When talking about particle size and water retention, smaller particles correlate with higher levels of water retention. Larger particles will allow for the water to more easily flow to lower layers. In addition to this, organic matter in soil tends to increase water retention, because organic matter tends to absorb water. The type of soil that has the most water retention is loam which has an equal amount of small, medium, and large particles.

Particle Sizes and Properties

Various particle sizes can impact the characteristics of soil in a big way. Some of the characteristics that are impacted by soil size include porosity, permeability, and fertility. 

Image Courtesy of Jesse Chippindale

Porosity describes how porous soil is. Larger particles have larger pore sizes, making soil more porous as the particle size increases. 

Permeability is the ability of nutrients and water to move down the soil horizons. Larger particles increase the permeability of soil because there is more space between the particles. Soil is more permeable the more space it has for water to move through.

The fertility of the soil considers its nutrient levels and to what extent it is able to support vegetation. These nutrients can include elements like phosphorus or nitrogen and can be impacted by how much biomatter is in the soil. Some soils also have a capacity at which their nutrient limit is reached.

Chemical, Physical, and Biological Properties of Soil

CHEMICAL PROPERTIES

Some of the chemical properties of soil include pH and cation exchange. Soil pH is how acidic or basic soil is. This can shift based on current environment or pollutants and it can have an impact on the plants that are able to grow. Often, acidic soil is caused by pollution and acid rain. Cation exchange is another chemical property of soil that can be complicated. In its simplest form, cation exchange occurs when soil particles attract cations (atoms with a positive charge). Cation exchange helps to regulate pH of soil; when a soil's cation exchange capacity is high, it is able to maintain stability in its nutrient levels and pH.

PHYSICAL PROPERTIES

Some of the physical properties of soil are aeration, soil compaction, permeability, and particle size. A few of these properties were discussed earlier.

Aeration is the ability of soil to take in essentials like nutrients, water, and oxygen. Soil with good aeration is able to take in needed amounts of sunlight and water which is key to fostering plant growth.

Soil compaction is how compacted the soil particles are. This can affect porosity, permeability, and aeration given space between individual particles. When soil is heavily compacted, there are few large pores and space is limited. Thus, there are fewer pockets of water, air, or other essential nutrients.

Permeability is also negatively impacted by this because tightly packed soil won't allow nutrients to get through.

BIOLOGICAL PROPERTIES

The biological properties of soil are determined by the organisms and plants that live in it. This means soil composition and consistency will vary depending on biome or climate. Species like fungi and bacteria can help develop a soil's composition in ways unlike other species'.

Soil Texture Triangle

Image Courtesy of Wikimedia

The soil texture triangle allows us to identify soil using the percentage of clay, silt, and sand. The angle of the numbers shows you the way the lines go for each type of particle. For example, clay lines go straight across, silt lines go down diagonally, and sand lines go up diagonally. To use a soil texture triangle, you follow the lines of each particle based on percent. The point where the lines intersect is the type of soil it is. For example, if we had a soil sample with 20% clay, 50% sand, and 30% silt, we would have loam.

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Key Terms to Review (9)

Aeration: Aeration refers to the process of increasing oxygen levels in something, such as soil or water. In the context of soil, aeration involves improving air circulation within the soil to enhance root respiration and nutrient uptake.

Cation Exchange Capacity (CEC): Cation Exchange Capacity (CEC) is a measure of how well a particular type of soil can retain and exchange cations (positively charged ions). It indicates the ability of the soil to hold onto essential nutrients for plant growth.

Fertility: Fertility refers to how well-suited soil or land is for supporting plant growth. It depends on the presence of essential nutrients, organic matter, and other factors that promote healthy plant development.

Permeability: Permeability refers to how easily fluids can flow through a material such as soil or rock. It measures how well interconnected the pores are within a substance.

Porosity: Porosity refers to the measure of how much empty space, or pores, there is in a material such as soil or rock. It indicates the ability of a substance to hold and transmit fluids.

Soil Compaction: Soil compaction refers to the process of soil particles being pressed together, reducing pore space and making it difficult for air, water, and plant roots to move through the soil.

Soil pH: Soil pH refers to the measurement of acidity or alkalinity in soil. It is a scale that ranges from 0 to 14, with values below 7 indicating acidic soil, values above 7 indicating alkaline soil, and a value of 7 being neutral.

Soil Texture Triangle: The soil texture triangle is a graphical tool used to classify different types of soils based on their proportions of sand, silt, and clay particles.

Water-Holding Capacity: Water-holding capacity refers to the ability of a soil to retain water for plant use. Soils with high water-holding capacity can hold more water, while soils with low water-holding capacity drain quickly.

4.4 Earth's Atmosphere

Major Gases

The Earth's atmosphere is mostly composed of oxygen and nitrogen. Nitrogen (N2) is released into the atmosphere through denitrification (recall the nitrogen cycle!). Oxygen (O2) is released through photosynthesis and plants.

Water vapor (H2O) can also be a major gas in the atmosphere. It is notably more concentrated around the equator than around the poles (where humidity and tropic-like conditions are common).

There are also many other gases that play important roles in the atmosphere including methane (CH4), carbon dioxide (CO2), nitric oxide (N2O), and ozone (O3). Carbon dioxide, methane, and nitric oxide are all greenhouse gases that trap heat in Earth’s atmosphere. All of these gases are released when fossil fuels are burned. Since humans have burned an abundance of fossil fuels, greenhouse gas emissions are high and our planet is warming.

Ozone (O3) absorbs harmful UV radiation given off by the sun. This layer reduces the amount of radiation that reaches the troposphere which is beneath the ozone layer. The ozone layer prevents a lot of negative side effects from the sun, but was significantly damaged by our use of CFCs (chlorofluorocarbons). 

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Layers of the Atmosphere

The atmosphere is composed of the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. 

The first layer of the atmosphere (closest to the earth) is the troposphere. The troposphere starts at ground level and goes up to around 10 kilometers in altitude, about the average height of a cruising airplane. This layer is the shallowest layer of the atmosphere. Within this layer, temperature decreases as altitude increases, as all weather occurs in this atmospheric layer. 

Above the troposphere is the stratosphere that goes from 10 kilometers in altitude to 50 kilometers in altitude. The stratosphere is mainly composed of Earth's ozone layer, which is used for protection from UV rays. Thanks to the ozone layer, the troposphere doesn’t receive 100% of the UV rays given off by the sun. This plays a big role in the temperature in the stratosphere, whose temperature increases with altitude unlike the troposphere,

Next is the mesosphere that goes from 50 kilometers to 80 kilometers in altitude. In this layer, the temperature decreases as you increase in altitude. This layer is very cold, and temperatures in the mesosphere can reach below -80 °C (-115 °F).

Then, the thermosphere goes from about 80 kilometers to 100 kilometers in altitude. Another name for the thermosphere is the ionosphere because this layer often traps protons, electrons, and other ions given off by the sun. As you increase in altitude in this layer, the temperature increases because this layer receives a lot of UV radiation and energy from the sun.

Finally, the exosphere is the highest layer of the Earth's atmosphere and is located around 700 and 10,000 km above Earth's surface. It is the upper limit of our atmosphere! At its top, it merges with the solar wind, and while no weather occurs here, the aurora borealis and aurora australis can be seen at its lowest point. Many satellites orbit this layer of the atmosphere and the molecules in this layer have extremely low density.

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Key Terms to Review (9)

Aurora Australis: The Aurora Australis, also known as the Southern Lights, is a natural light display similar to the Aurora Borealis but occurs in the southern hemisphere near Antarctica.

Aurora Borealis: The Aurora Borealis, also known as the Northern Lights, is a natural light display that occurs in the polar regions. It is caused by the interaction of charged particles from the sun with atoms in Earth's atmosphere.

Chlorofluorocarbons (CFCs): Chlorofluorocarbons (CFCs) are synthetic compounds made up of carbon, chlorine, and fluorine atoms. They were commonly used in aerosol propellants, refrigerants, and foam-blowing agents but have been phased out due to their harmful effects on the ozone layer.

Denitrification: Denitrification is a natural process in which certain bacteria convert nitrates (NO3-) into nitrogen gas (N2), releasing it back into the atmosphere. It occurs primarily in oxygen-depleted environments, such as wetlands and soil.

Fossil Fuels: Fossil fuels are energy-rich substances formed from ancient organic matter buried deep within the Earth's crust. They include coal, oil, and natural gas. Fossil fuels are burned to release energy but also release carbon dioxide and other pollutants into the atmosphere.

Greenhouse Gases: Greenhouse gases are gases in the Earth's atmosphere that trap heat and contribute to the greenhouse effect, leading to global warming. They include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and fluorinated gases.

Nitrogen Cycle: The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms in the environment. It involves nitrogen fixation, nitrification, assimilation, ammonification, and denitrification.

Ozone Layer: The ozone layer is a region in Earth's stratosphere that contains a high concentration of ozone (O3) molecules. It plays a crucial role in absorbing and filtering out most of the sun's harmful ultraviolet (UV) radiation before it reaches the Earth's surface.

Photosynthesis: Photosynthesis is the process through which green plants use sunlight, carbon dioxide, and water to produce glucose (sugar) and oxygen. It is vital for plant growth and releases oxygen into the atmosphere.

4.5 Global Wind Patterns

Solar Radiation

Due to the fact that the earth’s axis is tilted, heat and solar radiation is unevenly distributed. Because of our unique circumstances, heat accumulates at the equator naturally, thus leaving the poles without heat. The Earth uses various processes to circulate warm air towards the poles and move cooler air towards the equator.

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There are different kinds of convection cells found in the atmosphere that move air from the equator to the poles. These convection cells are polar cells, Ferrel cells, and Hadley cells. They are distinguished by where they are found.

• Hadley cells occur between 0° and 30° latitudes (directly north and directly south of the equator). At the equator, these cells start with warm, rising air. Then, as the air moves away from the equator, the air falls as cooler air.

• Ferrel cells occur between 30° and 60° latitudes. Around the 30° latitude line, the cold, dry air of a Hadley cell falls, pushing warm air up.

• Polar cells occur at latitudes greater than 60°. Polar cells start around the 60° latitude line where warm air from the Ferrel cells is pushed up. At higher latitudes, this air cools and falls as dry air on the poles.

Pressure and Wind Direction

Pressure in our atmosphere has a lot of effect on wind, which travels best from a high-pressure to a low-pressure environment. Think about a hill. One will go faster rolling downwards than attempting to roll up.

Looking at the image above, we can see the pressure created at a boundary between two convection currents. For example, between a Hadley and Ferrel cell, there is high pressure, but between two Hadley cells, there is low pressure. Thus, the wind will blow from the Ferrel-Hadley boundary (30° latitude) to the Hadley-Hadley boundary (0° latitude). This helps in keeping the convection cells separate, with different wind direction that allows Earth to redistribute its received heat energy.

Coriolis Effect

Imagine you are standing on a merry-go-round at the park. If you throw a ball straight ahead while the merry-go-round is spinning, the ball will appear to curve to the right (if you are in the Northern Hemisphere) or to the left (if you are in the Southern Hemisphere). This is because the ball is moving in a straight line relative to the ground, but the ground is moving in a circular path around the center of the merry-go-round.

The Coriolis effect works in a similar way. When an object is in motion relative to a rotating frame of reference, it appears to curve in a certain direction. This effect is most noticeable at long distances and at high latitudes, where the rotation of the Earth has the greatest influence.

It plays a role in the way that winds and ocean currents behave. As we established above, winds will go from the Ferrel-Hadley boundary (30° latitude) to the Hadley-Hadley boundary (0° latitude), or high to low pressure. These winds are called trade winds. If the earth wasn’t spinning, the winds would travel in a straight line; however, since the earth rotates, these winds do as well. If you look at the global circulation image, you will see that the lines representing wind currents are curved.

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Key Terms to Review (3)

Convection Cells: Convection cells are circular patterns of air or water movement caused by the uneven heating and cooling of a substance. Hot air or water rises, creating an area of low pressure, while cooler air or water sinks, creating an area of high pressure.

Coriolis effect: The Coriolis effect is the apparent deflection of moving objects, such as air or water currents, caused by the rotation of the Earth. It causes moving objects to be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

Trade winds: Trade winds are prevailing easterly winds that blow from east to west between 30 degrees latitude (both north and south) and the equator. They are named so because they were historically used by sailors for trade routes across oceans.

4.6 Watersheds

A watershed is a channel (stream, river) that concentrates runoff (water) to the main discharge point (a large body of water). Usually, the discharge point is at the lowest point in the watershed.

Headwaters are the beginning of a watershed. Watersheds are typically separated by ridges or mountains that form the highest part of the watershed. From here, runoff moves to lower elevations forming streams and rivers.

These streams and rivers can diverge and create sub-watersheds, but all of the runoff discharges into one point, a lake or ocean.

Image Courtesy of Pixabay

Characteristics of A Watershed

The characteristics of a watershed, like size, length, slope, rate, and present plant life, impact its production and efficiency.

• The size (area) of a watershed can be a reflection of the amount of runoff and what is created by the runoff, i.e. river, stream, or creek. It could also reflect how the runoff is discharged, i.e. the ocean or lake. It also plays a role in how much runoff can be held in the watershed.

• The length and slope of a watershed play a big factor in the runoff rate.

  • Runoff is increased by steeper slopes that allow water to flow downwards with the help of gravity.

  • The length of a watershed is the distance between the headwaters and the discharge point. This mainly impacts how long it takes for runoff to reach the discharge point. Hence, the longer the watershed, the longer it would take for runoff to be discharged.

• The type of soil found in watershed impacts the amount of runoff absorbed by soil as well as the vegetation. If the soil is very sandy or has large particles, the soil will take in more runoff water. In addition, if the soil is fertile, there will be more vegetation. Finally, soil can play a role in filtering water in a watershed.

  • Vegetation plays an important role in soil erosion. The more plants in a watershed, the lesser amount of erosion that will take place. Vegetation can also improve soil fertility and water filtration.

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Key Terms to Review (3)

Discharge Point: A discharge point is the location where water from a river or stream flows into another body of water, such as a lake, ocean, or another river. It is the endpoint of a watercourse.

Water Filtration: Water filtration is the process of removing impurities and contaminants from water to make it safe for consumption or other uses. It involves passing water through a physical barrier or using chemical processes to remove particles, bacteria, viruses, and other harmful substances.

Watershed: A watershed is an area of land where all the water that falls on it drains into a common outlet, such as a river, lake, or ocean. This term connects to various elements of hydrology and environmental science, highlighting how water systems interact with land use, pollution, and ecological health. Understanding watersheds is essential for managing water resources, protecting ecosystems, and mitigating the impacts of human activities on water quality.

4.7 Solar Radiation and Earth's Seasons

The main source of energy for our earth is from our sun; called solar radiation, it affects different biomes during any season in specific ways. In these four seasons, the length of a day's light/darkness changes, as does the angle of the Sun in comparison. In the winter, the sun's angle is not favorable, as night lengths are much longer and not as much solar radiation (heat, sunlight) is received. In summer, the opposite is true.

Latitude also plays an important factor in solar radiation reception since at the equator, or 0° latitude, solar radiation hits the surface straight on. Anyone on or near the equator will experience more solar radiation per unit of area. However, at higher and lower latitudes, the earth experiences curvature, so the same amount of solar radiation is spread over an area. That is to say, the equator at the horizontal center line of our planet receives more solar radiation because of its lack of curvature.

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Seasons and Earth’s Tilt

As the Earth orbits the sun, different parts of the Earth receive more or less direct sunlight, which causes the temperature differences also known as seasons. When the Earth tilts towards the sun, the daytimes are longer and the solar radiation hits the Earth's surface at a more direct angle, causing hotter temperatures. When the Earth tilts away from the sun, nights become longer and temperatures drop.

The transition periods between summer and winter occur when the Earth's tilt changes from pointing toward or away from the sun. These are the equinoxes, and they occur every spring and fall/autumn. These two days represent the closest margins of the year between the lengths of day and night. Don't confuse this with the solstices! The summer and winter solstices represent the highest and lowest points of the sun throughout the year, or the longest days and nights. The equinoxes mark the start of spring/fall where the day and night are approximately even in length.

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Key Terms to Review (4)

Biomes: Biomes are large-scale ecological communities characterized by distinct climate conditions, vegetation types, and animal species. They represent different regions across the globe with similar environmental characteristics.

Equinoxes: Equinoxes are two points in Earth's orbit around the Sun when day and night are approximately equal in length all over the world. They occur twice a year, marking the beginning of spring and autumn.

Solar Radiation: Solar radiation refers to the energy emitted by the Sun in the form of electromagnetic waves. It includes visible light, ultraviolet (UV) radiation, and infrared (IR) radiation.

Solstices: Solstices are the two points in the year when the Sun reaches its highest or lowest point in the sky at noon, resulting in the longest and shortest days of the year. The summer solstice occurs around June 21st and marks the beginning of summer, while the winter solstice occurs around December 21st and marks the beginning of winter.

4.8 Earth's Geography and Climate

Factors That Influence Climate

There are many factors that influence climate, but there are some geologic and geographic factors that can play a big role. 

The sun: The sun is the primary source of energy for the Earth's climate system. The intensity of the sun's radiation can vary slightly over time, which can have an effect on the Earth's climate. Additionally, variance in seasons and latitude (season intensity in the Arctic, versus the United States, versus Ecuador, versus the Antarctic...) as we discussed before clearly contributes to unique climates. Solar radiation and its dispersion can greatly influence a climate.

Earth's orbit: The shape of the Earth's orbit around the sun can affect the amount of solar energy that reaches the Earth's surface. The ellipse that our planet orbits on is not a circle, so climates can change depending on proximity.

Greenhouse gases: Greenhouse gases (like CO2 or methane gas) heat our atmosphere since it absorbs energy. Contributions like mass deforestations and burning of fossil fuels maintain that humans have contributed the most to climate change and global warming. While this does irreparable damage to our planet and community, it also creates hotter, more abrasive, and more dangerous climates worldwide. It can also increase the likelihood of natural disasters, which may change the climate of a certain region if not avoided.

Volcanoes: Large volcanic eruptions put out a lot of ashes and atmospheric gases, which cools the Earth's surface by blocking solar radiation. Be aware that this effect of the eruption will at most last several decades, and is not a permanent alteration to the climate. It also is not strong enough of a deterrent for our current situation regarding global warming.

Ocean currents: The movement of the Earth's oceans can have a significant influence on climate because of the ocean's large heat capacity, meaning that it can store heat energy present on Earth. For example, a stream could carry warmer water into a coastal region which in turn warms the climate.

Land masses: The shape and elevation of the Earth's land, like mountains can block the movement of air masses. This causes differences in temperature and precipitation on either side of the mountain range, and different conditions on the top of the mountain depending on its height (or altitude). The rain shadow effect results in one side of a mountain receiving more precipitation than the other side. On the windward side, warm, moist air rises up the mountain, cools, and falls as precipitation. However, on the leeward side, they don’t receive much precipitation because the air doesn’t have much moisture left.

Key Terms to Review (11)

Climate Change: Climate change refers to long-term shifts in temperature and weather patterns on a global scale. It is primarily caused by human activities, such as burning fossil fuels and deforestation, leading to an increase in greenhouse gas concentrations in the atmosphere.

CO2: CO2, or carbon dioxide, is a greenhouse gas that is released into the atmosphere through human activities such as burning fossil fuels and deforestation. It contributes to global warming by trapping heat in the Earth's atmosphere.

Earth's Orbit: Earth's orbit refers to the path or trajectory followed by our planet as it revolves around the Sun.

Global Warming: Global warming refers to the long-term increase in average global temperatures primarily caused by human activities, such as the burning of fossil fuels and deforestation. It leads to various environmental changes, including rising sea levels, melting glaciers, and more frequent extreme weather events.

Greenhouse Gases: Greenhouse gases are gases in the Earth's atmosphere that trap heat and contribute to the greenhouse effect, leading to global warming. They include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and fluorinated gases.

Land Masses: Land masses refer to large areas of land that are distinct and separate from bodies of water. They can include continents, islands, and peninsulas.

Methane Gas: Methane gas is another potent greenhouse gas that is released during natural processes (such as decomposition) and human activities (such as livestock farming and fossil fuel extraction). It has a much stronger warming effect than carbon dioxide but stays in the atmosphere for a shorter period of time.

Ocean Currents: Ocean currents are continuous, directed movements of seawater generated by various factors such as wind, temperature differences, and the Earth's rotation. They play a crucial role in distributing heat around the planet and influencing climate patterns.

Rain Shadow Effect: The rain shadow effect occurs when a mountain range blocks prevailing moisture-laden winds, causing one side of the mountain to be relatively dry while the other side receives abundant rainfall.

Solar Radiation: Solar radiation refers to the energy emitted by the Sun in the form of electromagnetic waves. It includes visible light, ultraviolet (UV) radiation, and infrared (IR) radiation.

Volcanic Eruptions: Volcanic eruptions are natural events where molten rock, ash, and gases are expelled from a volcano. They can cause significant damage to the surrounding environment and have long-lasting effects on climate.

4.9 El Niño and La Niña

El Niño

An El Niño is a warming of the Pacific Ocean between South America and Papua New Guinea (just north of Australia, an island in the Southwest Pacific). This occurs when the trade winds in that region weaken, which causes the west coast of South America to experience warmer waters. This effect also allows the thermocline to move deeper. This layer of the ocean represents a shallow depth at which a lot of heat is lost. By moving deeper, this demonstrates that the thermocline has receded into the depths and given rise to more warm ocean. This is shown in the image below. El Niño events cause higher precipitation in drier climates on the West Coast but create colder winters in the southeastern US.

La Niña

When a La Niña occurs, it is a cooling of the Pacific Ocean between Papua New Guinea and South America, essentially the opposite of an El Niño. The formation of a La Niña begins when the trade winds get stronger, which pushes warm coastal water further and further away from the South American coastline. Deeper and colder water from the ocean will rise, which is called upwelling. This means that the thermocline has instead moved up, creating less room for warm ocean. 

Instead of generally rising temperatures, we see cooler temperatures as well as wet conditions. However, in the southeastern US, we see the opposite, warmer and drier conditions.

Greater Environmental Impacts

An El Niño can have impacts that are shown around the world. The rapid change in climate may cause some species to suffer or require relocation due to their niche not allowing for extremely warm or cold environments. Additionally, migration seasons for birds may change entirely.

On a more global scale, the ocean heat capacity decreases and it is unable to absorb as much energy as needed, which in turn warms the planet. As for the weather, temperature changes will affect precipitations and contribute to either flooding or drought.

Key Terms to Review (9)

Climate Change: Climate change refers to long-term shifts in temperature and weather patterns on a global scale. It is primarily caused by human activities, such as burning fossil fuels and deforestation, leading to an increase in greenhouse gas concentrations in the atmosphere.

Drought: Drought is a prolonged period of abnormally low precipitation, resulting in water scarcity and dry conditions. It can have severe impacts on agriculture, ecosystems, water supplies, and human activities that depend on water.

El Niño: El Niño is a climate pattern characterized by warmer-than-normal ocean temperatures in the equatorial Pacific Ocean, which can cause significant changes in weather patterns worldwide.

Flooding: Flooding occurs when an area becomes submerged in water due to excessive rainfall, melting snow, dam failure, or other factors. It can lead to property damage, displacement of people and animals, contamination of water sources, and disruption of ecosystems.

La Niña: La Niña is a climate pattern that occurs when the surface waters of the Pacific Ocean become unusually cool, leading to changes in weather patterns around the world.

Migration: Migration refers to the movement of individuals or populations from one place to another, often driven by factors such as changes in environmental conditions, availability of resources, or the need for breeding grounds.

Ocean Heat Capacity: Ocean heat capacity refers to how much heat energy can be absorbed by seawater without significantly changing its temperature. The high heat capacity of oceans helps regulate Earth's climate by absorbing and storing large amounts of heat.

Thermocline: The thermocline is a layer within large bodies of water where there is a rapid change in temperature with depth. It acts as a barrier that separates warmer surface waters from colder deep waters.

Upwelling: Upwelling is the process in which cold, nutrient-rich water from the ocean depths rises to the surface. This brings nutrients to the surface, supporting the growth of phytoplankton and attracting marine life.