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Table of Contents


The Effects of Physical Geography

Atmospheric Features

Hydrospheric Features

Biospheric Features

Lithospheric Features

Human Impact on the Environment

Cyclone Phailin, 11 October 2013




Taken at the beginning of March 2008 during the windstorm called "Emma" near Rostock / Northern Germany – Emma Watson



The Effects of Physical Geography


Many of earth’s physical features affect at least to some degree a region’s culture, demographics, politics and economics. And the culture, demographics, politics and economics within a region can very definitely affect that region's physical features.

Since there is a separate 3-hour course on Physical Geography, we spend very little time on it in a human geography course, focusing mainly on those ways in which physical geography has an impact on human populations and vice versa. So let's start with the basics.

The earth is a closed system that we divide into 4 sub-systems: the atmosphere, the hydrosphere, the biosphere and the lithosphere (or geosphere).

The Four Spheres of Earth (5:49)

Earth's sub-systems















Atmospheric Features


CharacteristicsImage showing the temperature of the atmosphere throughout different layers

o   The atmosphere (air) is an important part of what makes earth livable. It blocks some of the sun's dangerous rays from reaching earth. It traps heat, making earth a comfortable temperature. And the oxygen within our atmosphere is essential for life.

o   The atmosphere is a mixture of nitrogen (78%), oxygen (21%), and other gases (1%) that surrounds earth.

o   The atmosphere is divided into five layers. It is thickest near the surface and thins out with height until it eventually merges with space. The troposphere is the first layer above the surface and contains half of the earth's atmosphere. Weather occurs in this layer. Many jet aircrafts fly in the stratosphere because it is very stable. Also, the ozone layer absorbs harmful rays from the sun. Meteors or rock fragments burn up in the mesosphere. The thermosphere is a layer with auroras. It is also where the space shuttle orbits. The atmosphere merges into space in the extremely thin exosphere. This is the upper limit of our atmosphere.

o   Weather is the state of the atmosphere at a given time and place. Most weather takes place in the troposphere, the lowest layer of the atmosphere. There are a lot of components to weather. Weather includes sunshine, rain, cloud cover, winds, hail, snow, sleet, freezing rain, flooding, blizzards, ice storms, thunderstorms, steady rains from a cold front or warm front, excessive heat, heat waves and more. Air temperature and pressure, the amount and type of precipitation, the strength and direction of wind, and the types of clouds are all described in a weather report. Weather changes each day because the air in our atmosphere is always moving, redistributing energy from the sun. In most places in the world, the type of weather events expected vary through the year as seasons change. While weather can change rapidly, climate changes slowly, over decades or more, in response to changes in the factors that determine our climate. The difference between weather and climate is a measure of time. Weather is what conditions of the atmosphere are over a short period of time, and climate is how the atmosphere "behaves" over relatively long periods of time.

o   The climate where you live is called regional climate. It is the average weather in a place over more than thirty years. To describe the regional climate of a place, people often tell what the temperatures are like over the seasons, how windy it is, and how much rain or snow falls. The climate of a region depends on many factors including the amount of sunlight it receives, its height above sea level, the shape of the land, and how close it is to oceans. Since the equator receives more sunlight than the poles, climate varies depending on distance from the equator.The Köppen Climate Classification System

o   The Köppen Climate Classification System (Click on map to the right.)

  1. Moist Tropical Climates are known for year round high temperatures and large amounts of rain, tropical rainforest climates (Af), tropical monsoon climates (Am) and savanna climates (Aw).

  2. Dry Climates are characterized by little rain and a huge daily temperature range.

    Two subgroups, semiarid/steppe (BWh, BWk) and arid/desert (BSh, BSk) are used with this climate.mountain river and water dam

  3. In Humid Middle Latitude (Temperate) Climates land and water differences play a large part. They create warm, dry summers and cool, wet winters. This includes Mediterranean climates (Csa, Csb), warm temperate climates (Cfa, Cwa) and oceanic climates (Cfb, Cfc, Cwb, Cwc).

  4. Continental Climates (low precipitation, varied seasonal temperatures): including hot summer continental climates (Dfa, Dwa, Dsa), warm summer continental climates (Dfb, Dwb, Dsb), continental subarctic climates (Dfc, Dwc, Dsc) and continental subarctic with extremely severe winters (Dfd, Dwd, Dsd): can be found in the interior regions of large land masses.

  5. Polar or Alpine Climates have permanent ice and tundra and have above freezing temperatures only about four months of the year. This includes tundra climates (ET) and ice cap climates (EF).

o   When we talk about climate change, we talk about changes in long-term averages of daily weather. Today, children always hear stories from their parents and grandparents about how snow was always piled up to their waists as they trudged off to school. Children today in most areas of the country haven't experienced those kinds of dreadful snow-packed winters, except for the Northeastern US in January 2005. The change in recent winter snows indicate that the climate has changed since their parents were young. In addition to long-term climate change, there are shorter term climate variations. This so-called climate variability can be represented by periodic or intermittent changes related to El Niño, La Niña, volcanic eruptions, or other changes in the earth system.

o   The National Academy of Sciences, a lead scientific body in the US, has determined that the earth's surface temperature has risen by about 1 degree Fahrenheit in the past century, with accelerated warming during the past two decades. There is new and stronger evidence that most of the warming over the last 50 years is attributable to human activities. Yet, there is still some debate about the role of natural cycles and processes.

o   Human activities have altered the chemical composition of the atmosphere through the buildup of greenhouse gases: primarily carbon dioxide, methane, and nitrous oxide. The heat-trapping property of these gases is undisputed although uncertainties exist about exactly how earth's climate responds to them. According to the US Climate Change Science Program, factors such as aerosols, land use change and others may play important roles in climate change but their influence is highly uncertain at the present time.


Atmospheric Hazards



freezing rain


high winds


excessive cold





El Niño, La Niña


ice storms


global warming



excessive heat

climate change



heat waves



Optional Resources:

NASA’s Exploring Ozone: a short and very good You Tube video

NASA’s Ozone Hole Site: updated daily

Ozzy Ozone: for kids but really good

Coastal Storms and Tsunamis

Climate and Land Use Change

Climate Variability and Change

USGS Global Change Science

USGS Tracks Acid Rain

Natural Hazards: Hurricanes

National Climate Change and Wildlife Science Center

Impacts and Predictions of Coastal Change during Hurricanes

Climate Change and Wildlife Health: Direct and Indirect Effects

A ‘Hyperactive’ Hurricane Season Is About to Strike

Hurricanes growing stronger, more intense; climate change may be a factor, study says

Tropical cyclones are already getting stronger, new dataset shows

Carbon Dioxide Emissions Have Dropped 17 Percent During the Pandemic

There’s a New Definition of ‘Normal’ for Weather

OK, you fix the climate.

An "Extreme Heat Belt" will soon emerge in the US, study warns

Much of the planet will endure climate-related extreme weather by 2040. This New York Times interactive shows the biggest threats that each country will face.

Extreme Heat Will Change Us

Where We'll End Up Living as the Planet Burns

The Enhanced Fujita scale measures how strong tornadoes can get.

Global warming to cause a US "Extreme Heat Belt," study warns

Scientists say the world is at risk of triggering multiple climate "tipping points.”

How hot will your city be in 2050? Check with these graphics from The Washington Post.

New research has found that Middle America could soon be too hot for humans to live in.

Temperatures in the Arctic are rising four times as fast as in the rest of the world.

Climate Change from A to Z

Have climate questions? Get answers here.

What Is the Wind Chill Index?

What is an atmospheric river?

Why do we still have brutal cold snaps even as the planet warms to record levels?

Weather West blog

Weather West channel

Can we engineer our way out of the climate crisis?

Have climate questions? Get answers here.

What to Know About Heat Waves














Hydrospheric Features



o   The hydrosphere is the water component of the earth. It includes the oceans, seas, lakes, ponds, rivers and streams. The hydrosphere covers about 70% of the surface of the earth and is home for many plants and animals.

o   The total amount of water has not changed since geological times. What we had then we still have. Water can be polluted, used and misused but not created or destroyed. Water in liquid and frozen forms exists in groundwater, glaciers, oceans, the atmosphere, lakes and streams. Saline water accounts for 97.5% of this amount. Fresh water accounts for only 2.5%. Of this fresh water 68.7% is in the form of ice and permanent snow cover in the Arctic, the Antarctic and mountainous regions. Groundwater (which is underground) accounts for 29.9% of fresh water. Only 0.26% of the total amount of fresh water on the earth is concentrated in lakes, reservoirs and river systems where it is most easily accessible.

o   The hydrologic cycle transfers water from one state or reservoir to another. Reservoirs include atmospheric moisture (snow, rain and clouds) oceans, rivers, lakes, groundwater, subterranean aquifers, polar icecaps and saturated soil. Solar energy -- in the form of heat and light (insolation) -- and gravity cause the transfer from one state to another taking hours to thousands of years. Most evaporation comes from the oceans and is returned to the earth as snow or rain. Sublimation refers to evaporation from snow and ice. Transpiration refers to the expiration of water through the minute pores or stomata of trees. Evapotranspiration is the term used by hydrologists in reference to the three processes together, transpiration, sublimation and evaporation. Water also moves through the cycle by  condensation,hydrological cycle precipitation, infiltration, springs, runoff, and subsurface flow. (Click on diagram to the right.)

o   The hydrologic cycle involves the exchange of energy, which leads to temperature changes. For instance, when water evaporates, it takes up energy from its surroundings and cools the environment. When it condenses, it releases energy and warms the environment. These heat exchanges influence climate.

o   The evaporative phase of the hydrologic cycle purifies water which then replenishes the land with freshwater. It takes around 2500 years for the complete recharge and replenishment of oceanic waters, 10,000 years for permafrost and ice, 1500 years for deep groundwater and mountainous glaciers, 17 years for lakes and 16 days for rivers.

o   The flow of liquid water and ice transports minerals across the globe. It is also involved in reshaping geological features of the earth, through processes including erosion and sedimentation.

o   The hydrosphere, like the atmosphere, is always in motion. The motion of rivers and streams can be easily seen, while the motion of the water within lakes and ponds is less obvious. Some of the motion of the oceans and seas can be easily seen while the large scale motions that move water great distances -- such as between the tropics and poles or between continents -- are more difficult to see. These types of motions are in the form of currents that move the warm waters in the tropics toward the poles, and colder water from the polar regions toward the tropics. These currents exist on the surface of the ocean and at great depths in the ocean.

o   The characteristics of the ocean which affects its motion are its temperature and salinity. Warm water is less dense or lighter and therefore tends to move up toward the surface, while colder water is more dense or heavier and therefore tends to sink toward the bottom. Salty water is also more dense or heavier and thus tends to sink, while fresh or less salty water is less dense or lighter and thus tends to rise toward the surface. The combination of the water's temperature and salinity determines whether it rises to the surface, sinks to the bottom or stays at some intermediate depth. The oceans currents are also affected by the motion of the atmosphere, or winds, above it. The energy in the wind gets transferred to the ocean at the ocean surface affecting the motion of the water there. The effect of wind is largest at the ocean surface.

o   The ocean serves two main purposes in the climate system. First, it is a large reservoir of chemicals that can contribute to the greenhouse effect in the atmosphere and energy absorbing 90% of the solar radiation which hits the surface. This reservoir changes very slowly limiting how fast the climate can change. Second, it works with the atmosphere to redistribute the energy received from the sun such that the heat in the topics, where a lot of energy is received from the sun, is transferred toward the poles, where heat is generally lost to space.

o   The ocean, which covers about 70% of the world’s surface, has absorbed more than 90% of the heat unleashed by the burning of fossil fuels, deforestation and other human activity.

o   Proximity to ocean or surface water stabilizes temperature extremes and provides transportation.

o   Presence and Distribution of Potable Water: Specific water availability is the residual (after use) per capita quantity of fresh water. Fresh water resources are unevenly distributed in terms of space and time and can go from floods to water shortages within months in the same area.

o   UN experts predict that most of the Earth's population will be living under conditions of a low or catastrophically low water supply by 2025.

o   Just as the global climate can change, so the global hydrologic cycle can change. Changes in salinity patterns is one change seen in recent years. Glacial retreat is also an example of a changing hydrologic cycle, where the supply of water to glaciers from precipitation cannot keep up with the loss of water from melting and sublimation. Glacial retreat since 1850 has been extensive. Human activities that alter the water cycle include agriculture, industry, alteration of the chemical composition of the atmosphere, construction of dams, deforestation and afforestation, removal of groundwater from wells, water abstraction from rivers and urbanization.

The World Water Crisis (4:03)


Hydrologic Hazards



lack of potable water

sea-level rise



lack of separated sewage / waste disposal systems


Optional Resources:

Human Impact on Coral Reefs (PDF)

Stream flow of 2011: Water Year Summary

Earth's Water: Surface Water

Fifty-Year Record of Glacier Change

Coastal Erosion

Ground Water Atlas of the US

Glaciers and Icecaps, Storehouses of Fresh Water

Texas Coastal Erosion

Benchmark Glaciers' Shrinking at Faster Rate

Ground-Water Data for the Nation

Coastal Change Hazards

Climate Change Indicators: Glaciers

Watershed Modeling Applications in South Texas

Surface Water Information Pages

Aquifer Basics

Edwards Aquifer Online Resources

Water-Quality Information

Science In Your Watershed

Ground Water Information Pages

30-Day Animations of US Daily Stream flow Maps

Wastewater Indicators Shown to Degrade in Streams

Earth's Water: Ground Water

Stream flow Statistics for US States

How Does a US Geological Survey Stream Gage Work?

Earth's Water: Runoff

USGS Activities in Texas

Images of Melt: Earth's Vanishing Ice

Effects of Brush Management on the Hydrologic Budget and Water Quality

Water Resources of Texas

Earthshots: Satellite Images of Environmental Change

Water Watch: Current Water Resources Conditions

Sediment and Nutrient Loading from Riverine Systems into Texas Estuaries and Bays

Primer on Water Quality

How glacier-fueled floods gouged out Greenland’s hidden canyons

Microplastics in the Ocean May Be Vastly Underestimated

Even the South Pole Is Warming, and Quickly, Scientists Say

See how climate change is weakening the Gulf Stream.

Old photos could reveal the future of these Arctic glaciers.

The iceberg A68a was one of the biggest ever seen when it broke off an ice shelf in 2017. Now it has completely melted.

How Bad Is the Western Drought? (02/2022)

Arctic Warming Is Happening Faster Than Described, Analysis Shows (08/11/2022)

Antarctica’s collapse could begin even sooner than anticipated.

Arctic summer could be practically sea-ice-free by the 2030s.

‘Doomsday glacier,’ which could raise sea level by several feet, is holding on ‘by its fingernails,’ scientists say.

‘Headed off the charts’: world’s ocean surface temperature hits record high

The Ocean’s Dire Message: Temperatures are the hottest they have been in recorded history, by a wide margin.

Drought saps the Panama Canal, disrupting global trade.

As groundwater dwindles, powerful players block change.

Great Pacific Garbage Patch

Glacial Longings

What This Year’s ‘Astonishing’ Ocean Heat Means for the Planet
















Biospheric Features




o   the life sphere

o   presence and distribution of valuable resources: forests, food resources, fur, leather, biodiversity

o   an open system with cycling and recycling in different forms

o   negative and positive feedback loops

o   self-regulating

o   Made atmosphere what it is today and appear to stabilize some perturbations such as CO2 production.

o   Primarily powered by energy from the sun. Light from the sun is transformed into plant matter. Animals get their energy ultimately from plants and the sun.

o   Interactions involve complex cycling of substances, biogeochemical cycles ... nutrient cycling: CHONSP (carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorous).

o   four essential properties of all living organisms

metabolize: chemical reactions by which energy is provided for life processes

grow: ordering of atoms and molecules to make bigger molecules

reproduce: single-celled organisms divide, multi-celled organisms use sexual or asexual reproduction

evolve: change over time as certain individuals in a population reproduce more than others



Plants and animals don't live in isolation ... they live together with other plants and animals in an interdependent group called an ecosystem. If you think about it for a moment, you will realize that all of the plants and animals in a particular ecosystem must be adapted to the same climate since they all live in the same location.

Any group of living and nonliving things interacting with each other can be considered an ecosystem. Ecosystems can be simple or complex, terrestrial or aquatic, large or small. Every ecosystem includes abiotic elements (air, water, rocks, energy) and biotic elements (plants, animals, microorganisms). The abiotic elements of an ecosystem can be listed as SWATS.






A change in any of the elements (for example: nutrient availability, temperature, light intensity, grazing intensity) results in changes in the nature of the ecosystem.



Biomes are the various areas of our planet which can best be distinguished by their climate, fauna and flora. A biome consists of a group of ecosystems that have the same general climate, and contain a particular group of plant and animal species.  Where ecosystems focus on the relationships among their various elements, biomes -- each consisting of a group of ecosystems adapted to similar conditions -- focus on geographic area.


Introduction to Biomes (3:10)


A biome is characterized by certain soil and climate conditions. An organism cannot live in just any biome. Each species of organism has a set of particular adaptations that make it well suited for a particular biome. Each plant and animal species has a different tolerance level. Tolerance is the ability to survive and reproduce in conditions that are less  than optimum for that organism. For example, an animal adapted to living in a desert has a high tolerance if it can tolerate blistering hot temperatures during the day and freezing temperatures at night. An insect that lives in a rain forest, however, would die quickly if the temperature became too cold.

SUCCESSION RESULTING IN A CLIMAX COMMUNITYA biome has climax communities with little or no succession taking place. The climax community is itself the result of succession. In succession, the ecosystem goes through a series of stages until it reaches a stable end point. At each stage of succession, the organisms present alter the physical environment in ways that make it less favorable for their own survival, but more favorable to the survival of the species that follow them. The plant and animal species of this ecosystem are stable populations that will remain constant over a long period of time.

Events called disturbances may change the face of a particular ecosystem. Examples of disturbances include forest fires, floods and volcanic eruptions. These events have drastic effects on the organisms living in the ecosystem. When disturbances happen, nature starts over (succession) in restoring living organisms to the area.

WORLD BIOMESScientists have divided the broad spectrum of climates and ecosystems found on earth into biomes in different ways. Similar biomes often exhibit unique qualities which set them apart but not necessarily enough to distinguish them completely from others. Because of this, scientists argue about the exact number and types of biomes.

However, we divide them, the importance of biomes cannot be overestimated. Biomes have changed and moved many times during the history of life on earth. More recently, human activities have drastically altered these communities.

Biomes and Biodiversity (PDF)

Decade of Destruction (1990): Part of PBS’ Frontline series, it chronicles the destruction of the Amazon rainforest - perhaps the 20th century's worst environmental disaster. (If PBS isn’t streaming the series when you wish to see it, you can catch the entire series on Hulu.)


Biogeochemical Cycles


Biogeochemical Cycles

The Food Chain


Water Cycle

Carbon Cycle

Nitrogen Cycle

Phosphorus Cycle

Sulfur Cycle

Chart Combining All Cycles



The Effects of Human Activities on the Biosphere

  1. human population growth leading to resource depletion: water, fossil fuels, food, habitat depletion

    1. Humans currently use approximately 40% of the sun's energy that is captured by organisms on land. Use of such an inordinately large proportion of the earth's productivity by a single animal species is unique in the history of the planet.

    2. The use by humans of a large percentage of earth's natural resources has decreased the natural resources other species need to survive -- land, water, food sources and available mates to reproduce. The use or destruction by humans of so much of those resources threatens the ability of other species to survive.

    3. Roads are often built through forests for industrial purposes, such as mining or mineral exploration, oil and gas interests. Uncontrolled development results in deforestation, with subsequent erosion and loss in biodiversity.

  2. human population growth leading to pollution: air, land, water

    1. the use of pesticides/herbicides to kill pests and unwanted plants: The problem is that chemicals accumulate in groundwater, thus affecting almost every element of any ecosystem in that area.

    2. biomagnification: The concentration of a pollutant is multiplied as it passes up the food chain. For example, each herring eats many zooplanktons, each porpoise eats many herring, and so on up the food chain. Top level consumers end up with the highest concentration of the pollutant.

    3. acid rain: Nitrogen and sulfur emissions (from human activity) enter the atmosphere, collect with water vapor and fall as acid rain ... inevitably killing the plants in that ecosystem and potentially starving the herbivores that depend on them. Acid rain also:

      leaches away valuable minerals in the soil

      increases toxic materials taken up by plant roots

      contributes to the discharge of aluminum, mercury and zinc from surrounding watersheds into lakes and rivers (Aluminum and low pH are toxic to rainbow trout.)

      results in a break in the food chain leading to the loss of aquatic species in lakes

      creates wet deserts: aquatic environments that no longer have living vegetation, fish or other organisms

      causes acid shock events: occur in the spring when snow and ice melt release stored acid deposits all at once (Occurs at the same time amphibians (i.e. frogs, toads, salamanders) are being born.)

  3. Invasive species can be in the form of a plant, animal, disease or insect.

    1. Humans move many species from their native ranges to places all over the earth, both deliberately and accidentally. Where those species establish new, self-maintaining populations, they constitute a biological invasion.

    2. The majority of species introductions fail. Plant and animal specie success rates over 50% are rare. Usually only 10-40%. of game fish, birds or mammals can survive as an invader in a new community due to an inability to adapt to the area.

    3. The species most likely to be successful invaders have high reproductive rates, short generation times, high genetic variability and broad diets. Further, they are long-lived, habitat generalists and introduced by humans.

  4. Climate changes affect each biome and each species individually. Different species and populations migrate, begin and become extinct at different rates.

    1. Climate changes can cause the extinction of existing ecosystems and the formation of new ecosystems.

    2. Ecological changes in climate (temperatures, flooding, warming, freezing) eliminate some species, and the loss of these species can cause the elimination of entire ecosystems. For example we could lose cold-adapted systems such as arctic and alpine communities to global warming, and low-laying areas or islands to flooding caused by a rise in sea level. Such changes could have a significant effect on earth's current biosphere and its ecosystems. All climate changes affect each specie's way of life -- the way each eats, survives and interacts with each other. Plastic and the Biosphere


Biospheric Hazards


loss of species diversity





invasive species




Optional Resources:

You Tube: Biodiversity Begins with a B

Human Impact on Forests (PDF)

Get Smart: Smart Growth/Sustainable Development

Map of Texas Ecosystem Regions (PDF)

Stages of Plant Succession and Associated Wildlife Species (PDF)

The Ecology of Ponds and Lakes (PDF)

Climate Change and Wildlife Health: Direct and Indirect Effects

Vertical Layering in a Typical South Plains Habitat (PDF)

Northern Gulf of Mexico Ecosystem Change and Hazard Susceptibility

The State of Amphibians in the US

Status and Trends of the Nation's Biological Resources

Farm Ponds as Critical Habitats for Native Amphibians

National Land Cover Characterization

BioData: Aquatic Bioassessment Data

Butterflies and Moths of North America

Our Dynamic Desert Landscape

Drought Monitoring with VegDRI

Unearthing Secrets of the Forest

Corals as Climate Recorders

Climate-Driven Ocean Changes Affect Estuaries

Land-Cover Change Research at the US Geological Survey

The Fragile Fringe: A Guide for Teaching about Coastal Wetlands

Introduction to Biogeochemical Cycles

American trees are moving west, and no one knows why

Dying coral reefs turn vibrant neon colors in apparent last-ditch effort to survive

Why some animals are more important to ecosystems than others (Keystone species)

Pollution: Birds 'ingesting hundreds of bits of plastic a day'

Crown Shyness: When Trees Need Personal Space

A whopping 91% of plastic isn't recycled.

A visual story on how human development is wreaking havoc on the Amazon rainforest and on Earth’s climate

The Social Life of Forests

The insect apocalypse is here.

This Map Shows Where Biodiversity Is Most at Risk in America

Amazon Is Less Able to Recover From Droughts and Logging, Study Finds

Even the Cactus May Not Be Safe From Climate Change

Researchers report a staggering decline in wildlife. Here’s how to understand it.

Out of Sight

Florida has become a zoo. A literal zoo.

Hawaii, dubbed the extinction capital of the world, has lost more species than any other state.

Hydrilla, a rapidly spreading invasive plant, is choking New England’s longest river. Government scientists are fighting back.

Scientists make stunning discovery in remote forest: ‘There are no others that have had the opportunity to live so long.’

Does success spell doom for Homo sapiens?

Beyond the Horizon

Time to a Pin Oak

The Extraordinary Lives of Coast Redwoods












Bryce Canyon National Park



Lithospheric Features


o   The lithosphere (rock) is the ground you are standing on and the whole inside of the earth. The earth's lithosphere includes the crust and the uppermost mantle, which constitute the hard and rigid outer layer of the Earth. The lithosphere is subdivided into lithospheric plates and is believed to "float" on top of the warmer, non-rigid and partially melted material directly below.

o   The thickness of the crust varies. Under the oceans, the crust is only about 3–5 miles thick. Under the continents, however, the crust thickens to about 22 miles and reaches depths of up to 37 miles under some mountain ranges.

o   The motion of the lithospheric plates is known as plate tectonics and is responsible for many of the movements seen on earth's surface, including earthquakes, certain types of volcanic activity and continental drift.

o   The theory of plate tectonics explains how and why crustal plates move around the earth. It also explains why the Pacific Ocean has so many volcanoes, large earthquakes and tsunamis. It gives us a basic understanding of how our planet is changing. It explains how mountains form, why crustal plates move and where great earthquakes are likely to strike. It explains the presence or absence of landforms, which can unify/fragment a nation, can protect/expose a nation and can facilitate/hinder trade, access, communication, etc. Finally, it explains the presence and distribution of valuable resources – oil, coal, natural gas, precious metals/gems, etc.

o   Plate boundaries:

o   divergent boundary: two plates separate

Along these boundaries, lava spews from long fissures and geysers spurt superheated water. Frequent earthquakes strike along the rift. Beneath the rift, magma — molten rock — rises from the mantle. It oozes up into the gap and hardens into solid rock, forming new crust on the torn edges of the plates. Magma from the mantle solidifies into basalt, a dark, dense rock that underlies the ocean floor. Thus at divergent boundaries, oceanic crust, made of basalt, is created.

Examples include the East Africa rift in Kenya and Ethiopia, and the Rio Grande rift in New Mexico. Where a divergent boundary crosses the ocean floor, the rift valley is much narrower, only a kilometer or less across, and it runs along the top of a mid-oceanic ridge. Oceanic ridges rise a kilometer or so above the ocean floor and form a global network tens of thousands of miles long. Examples include the Mid-Atlantic ridge and the East Pacific Rise.

o   convergent boundary: two plates come together

The impact of the two colliding plates buckles the edge of one or both plates up into a rugged mountain range, and sometimes bends the other down into a deep seafloor trench. A chain of volcanoes often forms parallel to the boundary, to the mountain range, and to the trench. Powerful earthquakes shake a wide area on both sides of the boundary.

If one of the colliding plates is topped with oceanic crust, it is forced down into the mantle where it begins to melt. Magma rises into and through the other plate, solidifying into new crust. Magma formed from melting plates solidifies into granite, a light colored, low-density rock that makes up the continents. Thus at convergent boundaries, continental crust, made of granite, is created, and oceanic crust is destroyed.

An example of this type of collision is found on the west coast of South America where the oceanic Nazca Plate is crashing into the continent of South America. The crash formed the Andes Mountains, the long string of volcanoes along the mountain crest, and the deep trench off the coast in the Pacific Ocean. The Rockies in North America, the Alps in Europe, the Pontic Mountains in Turkey, the Zagros Mountains in Iran, and the Himalayas in central Asia were formed by plate collisions.

o   transform boundary: two plates slide past each other

Natural or human-made structures that cross a transform boundary are offset, split into pieces and carried in opposite directions. Rocks that line the boundary are pulverized as the plates grind along, creating a linear fault valley or undersea canyon. As the plates alternately jam and jump against each other, earthquakes rattle through a wide boundary zone. In contrast to convergent and divergent boundaries, no magma is formed. Thus, crust is cracked and broken at transform margins, but is not created or destroyed.

Transform boundaries are marked in some places by linear valleys along the boundary where rock has been ground up by the sliding. In other places, transform boundaries are marked by features like stream beds that have been split in half and the two halves have moved in opposite directions. Perhaps the most famous transform boundary in the world is the San Andreas fault. The slice of California to the west of the fault is slowly moving north relative to the rest of California. Since motion along the fault is sideways and not vertical, Los Angeles will not crack off and fall into the ocean as popularly thought, but it will simply creep towards San Francisco at about 6 centimeters per year. In about ten million years, the two cities will be side by side!


o   The above processes also create the rocks we find on earth.

o   Igneous rocks are formed from melted rock that has cooled and solidified. When rocks are buried deep within the Earth, they melt because of the high pressure and temperature; the molten rock (called magma) can then flow upward or even be erupted from a volcano onto the Earth's surface. When magma cools slowly, usually at depths of thousands of feet, crystals grow from the molten liquid, and a coarse-grained rock forms. When magma cools rapidly, usually at or near the Earth's surface, the crystals are extremely small, and a fine-grained rock results. A wide variety of rocks are formed by different cooling rates and different chemical compositions of the original magma. Obsidian (volcanic glass), granite, basalt, and andesite porphyry are four of the many types of igneous rock.

o   Sedimentary rocks are formed at the surface of the Earth, either in water or on land. They are layered accumulations of sediments -- fragments of rocks, minerals, animal or plant material. Temperatures and pressures are low at the Earth's surface and sedimentary rocks show this fact by their appearance and the minerals they contain. Most sedimentary rocks become cemented together by minerals and chemicals or are held together by electrical attraction; some, however, remain loose and unconsolidated. The layers are normally parallel or nearly parallel to the Earth's surface; if they are at high angles to the surface or are twisted or broken, some kind of Earth movement has occurred since the rock was formed. Sedimentary rocks are forming around us all the time. Sand and gravel on beaches or in river bars look like the sandstone and conglomerate they will become. Compacted and dried mud flats harden into shale. Scuba divers who have seen mud and shells settling on the floors of lagoons find it easy to understand how sedimentary rocks form.

o   Sometimes sedimentary and igneous rocks are subjected to pressures so intense or heat so high that they are completely changed. They become metamorphic rocks, which form while deeply buried within the Earth's crust. The process of metamorphism does not melt the rocks, but instead transforms them into denser, more compact rocks. New minerals are created either by rearrangement of mineral components or by reactions with fluids that enter the rocks. Some kinds of metamorphic rocks -- granite gneiss and biotite schist are two examples -- are strongly banded or foliated. (Foliated means the parallel arrangement of certain mineral grains that gives the rock a striped appearance.) Pressure or temperature can even change previously metamorphosed rocks into new types.

o   One of the most important natural resources we have is soil. An important factor influencing the productivity of oursoil materials planet's various ecosystems is the nature of their soils. Soils are vital for the existence of many forms of life that have evolved on our planet. Soil is very complex. It would be wrong to think of soils as just a collection of fine mineral particles. Soil also contains air, water, dead organic matter and various types of living organisms. (See diagram to right.) The formation of a soil is influenced by organisms, climate, topography, parent material, and time. The presence and distribution of arable soil through out the globe is important.

o   The quality of soil affects energy budgets, nutrient cycling, water exchange, ecosystem productivity and etc. Most life on earth depends on soil as a direct or indirect source of food. Examples: plants (producers), animals, microbes, seeds, spores, insects, worms.

o   Soil pollution is defined as the build-up in soils of persistent toxic compounds, chemicals, salts, radioactive materials or disease causing agents, which have adverse effects on plant growth and animal health. Three factors determine the severity of a pollutant: its chemical nature, the concentration and the persistence. Causes of soil pollution:

o   war: Wars are probably the immediate cause of soil pollution.

o   burning fossil fuels: Burning fossil fuels, especially coal, produces sulfur dioxides and nitrogen oxides which rise into the atmosphere and react chemically with water vapor to form sulfuric acid and nitric acid. These return to earth as acid rain.

o   mining and extraction activities

o   recycling industrial byproducts into fertilizers

o   chemicals causing soil pollution: chlorinated hydrocarbons (CFH), heavy metals (such as chromium, cadmium in rechargeable batteries and lead found in paint, aviation fuel and gasoline), MTBE, zinc, arsenic and benzene

o   Ordinary municipal landfills are the source of many chemical substances entering the soil environment (and often groundwater).

o   There have also been some unusual releases of polychlorinated dibenzodioxins, commonly called dioxins for simplicity, such as TCDD.

o   Pollution can also be the consequence of a natural disaster ... for example: hurricanes resulting in water contamination from sewage, petrochemical spills from ruptured boats or automobiles, nuclear power plants or oil tankers.

o   Lithosphere Processes and Products

Lithospheric Processes and Products



Lithospheric Hazards

irregular and indented coastlines

shatter belt fragmentation

sinkholes/blue holes



soil degradation





lava flow

mud flow




Optional Resources:

This Dynamic Planet: World Map of Volcanoes, Earthquakes, Impact Craters and Plate Tectonics

An Estimate of Undiscovered Conventional Oil and Gas Resources of the World, 2012

Integrated Geologic, Geochemical and Geophysical Studies of Big Bend National Park, TX

Fault and Fold Database of the US

Earthquake Glossary

Precambrian Time: The Story of the Early Earth

The Geologic Time Spiral: A Path to the Past

What on Earth is Plate Tectonics?

US Gulf of Mexico Shoreline Change

Kilauea -- An Explosive Volcano in Hawaii

Erosion of a Sea Stack Over 100 Years

Deserts, Geology and Resources

The Great Ice Age

Interior of the Earth

The Earth's Crust

Divisions of Geologic Time

Geologic Time Online Edition

Landsat Data Continuity Mission

Mass Wasting Presentation

Geologic Hazards at Volcanoes

Coastal Erosion

Topographic Science



Earthquake Information by Topic

Fossils, Rocks and Time


The Raspberry Shake Network: the largest real-time seismic network in the world

Land Subsidence in the US

A massive blue hole just showed up near Mexico. New life forms may be inside.

There is a ‘gravity hole’ in the Indian Ocean, and scientists now think they know why.

Earth's hidden eighth continent is no longer lost.

Earth’s next supercontinent could wipe out mammals in 250 million years.

A strange plastic rock has ominously invaded 5 continents


Dwelling on Earth: Soil is what turns the Earth’s barren rock into the riotous life we know.

We know where the next big earthquakes will happen - but not when.

The Mysterious, Deep-Dwelling Microbes That Sculpt Our Planet















Human Impacts on the Environment


The human population continues to expand at the rate of approximately 80 million persons per year and may reach 10 billion sometime in the 21st century. Changes to the atmosphere caused by complex technology and the increasing population threaten to cause major disruptions to ecosystems. Among the most important changes are global warming and the release of greenhouse gases — including carbon dioxide, methane, and chlorofluorocarbons — into the atmosphere.Antarctic ice shelf

Environmental Philosophy

Human Impact on the Environment Part I

Human Impact on the Environment Part II

Human Impact on the Environment Part III

Human Impact on the Environment Part IV


Shall we pursue mitigation or adaptation?

  1. mitigation: pursue actions that reduce greenhouse gas emissions to stop or lessen severity of future climate change

examples: renewable energy, efficiency, farm practices to protect soil integrity, preventing deforestation, etc

  1. adaptation: accept that climate change is happening and pursue strategies to minimize its impacts

examples: use technology and engineering, adjust farming to cope with droughts, etc

often criticized as sidestepping


Market mechanisms could address climate change.Top Solutions to Climate Change

  1. replace income taxes with carbon taxes

  2. a cap and trade emissions trading program

Each state decides who needs to participate.

Each sets a cap on allowable carbon emissions.

Each emissions source gets one permit.

Each emissions source can buy or sell permits.

Any emissions source emitting more than its permitted amount will face penalties.

  1. emissions trading programs allow participants to buy carbon offsets

  2. carbon offset: a voluntary payment to enable another entity to reduce emissions that one is unable to reduce oneself

popular among utilities, businesses, universities, governments and individuals trying to achieve carbon-neutrality: no net carbon is emitted

simple, convenient (but expensive) way to reduce emissions without changing habits

  1. Carbon offsets fall short.

need oversight to make sure that the offset money accomplishes what it is intended for


Human-Induced Hazards

global warming

use of CFC's and impacts on the ozone layer

overuse of pesticides

use of PCB's


destruction of wetlands

urban encroachment

endangered species

acid rain

water contamination

use of fossil fuels

dams for hydro electricity

disposal of radioactive wastes

oil spills

smog and air pollution

soil erosion

introduction of invasive species

heavy metals

fragmentation of habitats

spread of diseases

salting Roads

crop irrigation

irrigation, land erosion and pesticide run off

abandoned mines and quarries

contamination and pollution


industrial pollution

land use change

mine drainage

mining hazards

nonpoint-source pollution

oil spills


pesticides and herbicides


toxic radionuclides

toxic trace elements

waste treatment and disposal

climate change

species extinction








Maplecroft Climate Change Vulnerability Index 2022




Optional Resources:The Production Gap

Wall Street firms are flip-flopping on climate amid Republican attacks.

Supreme Court seems ready to block a Biden plan on air pollution.

Carbon-free electricity - from wind, solar and hydroelectric sources - has never been more plentiful. But the use of fossil fuels is still rising globally, as these charts show.

Burning fossil fuels almost ended all life on earth.

How Silent Spring Ignited the Environmental Movement

Which food is better for the planet?

The Last 8 Years (2015-2022) Were the Hottest on Record

Exxon Scientists Predicted Global Warming, Even as Company Cast Doubts, Study Finds

The Encyclopedia of Earth



Beyond Catastrophe: A New Climate Reality Is Coming Into View

World at risk of triggering multiple climate "tipping points"

Much of the planet will endure climate-related extreme weather by 2040. This New York Times interactive shows the biggest threats that each country will face.

The Living Planet Report

24 Charts Every Leader Should See

9 Environmental Boundaries We Don’t Want to Cross

Maps: How Mankind Remade Nature

6 Ways We’re Already GeoEngineering Earth

Mass Species Loss Stunts Evolution for Millions of Years

Two Billion Years Ago, Up To 99% of Life on Earth Died In an Event More Catastrophic Than Mass Extinction of Dinosaurs

Sixth Mass Extinction "That Will Eradicate 75% of Life on Earth is Drawing Closer"


Portland Now Generates Electricity from Turbines Installed In City Water Pipes

Infographic: Lack of Clean Water Access Worldwide

Germanwatch Global Climate Risk Index 2016           

Climate Change Threatens Emerging Superpowers, While Large Regions Could Be Drought-Stricken by 2030.

Watch: Climate Change, Explained by a Kid (2:11)

Massive fracture in Antarctic ice shelf

Massive fracture in Antarctic ice shelf

Map Reveals Stark Divide in Who Caused Climate Change and Who's Being Hit.

Cool Climate Network

A Student's Guide to Global Climate Change

The WWF’s Footprint Calculator

The Nature Conservancy’s Carbon Footprint Calculator

Earthshots: Satellite Images of Environmental Change

The link between climate change and violence

Both poles are having a weird, bad year for sea ice so far.

Sea Ice Maximum Extent 2018

The giant garbage vortex in the Pacific Ocean is over twice the size of Texas. Here's what it looks like.

75% of Earth's land areas are degraded.

The Internet of Wild Things: Technology and the battle against biodiversity loss and climate change

These 10 technologies are most likely to help save planet Earth

Microsoft's ambitious plan to remove its entire carbon footprint

How Severe Is the Western Drought? See For Yourself. (06/11/2021)

New Yorkers got record rain, and a warning: Storms are packing more punch. (2022)

The Future of Mass Transit

The climate crisis is reshaping the planet. Here’s what it looks like in 193 countries.

Here’s how climate change affects every country.

We looked at 1,200 possibilities for the planet’s future. These are our best hope.

Here are 3 dangerous climate tipping points the world is on track for.





Copyright © 1996 Amy S Glenn
Last updated:   07/10/2024 0430

Creative Commons License