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Table of Contents
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)
Atmospheric Features
Characteristics 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. o The Köppen Climate Classification System (Click on map to the right.)
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
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Hydrospheric FeaturesCharacteristics 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, 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
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Biospheric Features
Characteristics 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
Ecosystems 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 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.
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.
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.)
The Effects of Human Activities on the Biosphere
Biospheric Hazards
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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 our 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 Hazards
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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. 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?
Market mechanisms could address climate change.
Human-Induced Hazards
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We can get the electricity we need without frying the planet (or our pocketbooks). Postcards from a World on Fire 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. 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 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 Map Reveals Stark Divide in Who Caused Climate Change and Who's Being Hit. 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.
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 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. Climate Disasters’ Cascading Effects
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A 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.
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.
