Chapter2

World Regional GeographyChapter 2: Physical Processes That Shape World Regions

• Lithosphere– Earth’s outer “rind” of rock– Varies in thickness from about 50 to 125 miles– Subdivided into categories of continental and oceanic

• Hydrosphere– Comprised of oceans and other water features

• Atmosphere– Layer of gases, primarily nitrogen and oxygen– Surrounds the earth to roughly 60 miles out

Spheres Making Up Earth’s Habitable Environment

• Continental Drift– Theory by Alfred Wegener, 1912– Continents once joined as supercontinent of “Pangaea”

but they “drifted apart” over time– Earth’s lithosphere is made up of several plates that

move in various directions

• Seafloor Spreading– Process of two plates moving away from each other– Few impacts on people

• Converging Plates– Trigger some of the planet’s greatest natural hazards– Subduction (one plate “dives” below another)

2.1.1 Plate Tectonics

• Seismic Activity– Refers to the earth’s vibrations when plates collide– Can result in earthquakes, tsunamis, and volcanism

• Earthquakes– Measured on the Richter Scale– World’s Largest Recorded Earthquakes

• Magnitude 9.5 Chile, 1960• Magnitude 9.2 United States, 1964• Magnitude 9.1 Indonesia, 2004

• Tsunamis (Tidal Waves)• Volcanism

– Movement of molten earth material– Generally occurs along / near subduction zones

2.1.1 Plate Tectonics (continued)

Tectonic Plates & Their Movement

Earthquakes, volcanoes, and other geologic events are concentrated where plates separate, collide, or slide past one another. Where they separate, rifting produces very low land elevations or the emergence of new crust on the ocean floor.

Concentric Layers of the Earth

• Hill Lands and Mountains– High and steep features– No formal distinction between “hills” and “mountains”

• Usage of terms based on local perceptions

– Most mountain areas are sparsely populated– Tend to be near areas of tectonic plate convergence

• Plains– Relatively level areas of slight elevation– Most of the world’s population lives on plains

• Plateaus– Elevated plains at an elevation above 2,000 feet– Typically terminated on one side by an escarpment

that marks a sharp boundary with lower elevation

2.1.2 Major Landform Types

• Weather– Atmospheric conditions occurring at a given time & place

• Climate– Average weather of an area over a long period of time

• Forces shaping the environment and human interaction with it include:– Precipitation– Aridity– Seasons– Climate & Vegetation Types

2.2 Patterns of Climate and Vegetation

• Precipitation– Result of processes that cool the air to release moisture

– Types of precipitation include: Rain, Snow, Sleet & Hail

• Processes of Precipitation– Convectional

– Orographic Mountain-Associated

– Cyclonic Frontal• Cold Front• Warm Front

2.2.1 Precipitation

World Precipitation Map

Some geographers argue that this is perhaps themost important of all maps in understanding life on earth.

Supercell Thunderstorm Complex

Types of Precipitation

Cyclone in the Northern Hemisphere

Hurricane Fran September 1996

• Aridity– Refers to low precipitation

– Drought or any other significant shortages in rainfall

• High Pressure (Anticyclones)– Air descends, becomes warmer, can hold more water vapor

• Atmospheric Stability in Coastal Regions– Caused by cold ocean waters

– Examples: Atacama Desert (Chile), Namib Desert (Africa)

• Rain Shadow– Windward Side much wetter than Leeward Side

– Examples: Sierra Nevada, Atlas Mountains

2.2.2 Aridity

Wind and Pressure Systems(shading indicates wetter areas)

• Solstices (Tip of earth’s axis inclined toward the sun)

– On or Around June 22 – Northern Tip of Axis• Summer Solstice (Northern Hemisphere)• Winter Solstice (Southern Hemisphere)

– On or Around December 22 – Southern Tip of Axis• Winter Solstice (Northern Hemisphere)• Summer Solstice (Southern Hemisphere)

• Equinoxes (Earth’s axis doesn’t point toward or away from sun)

– Days and nights are of equal length– On or about September 23 and again on or about March 20

• Regional Differences in World’s Temperatures– Near the Equator High temperatures all year– Polar Areas Low temperatures most of year– Middle Latitudes Defined seasonal changes

2.2.3 Seasons

Earth vs. Sun at the Solstices

Summer SolsticeNorthern Hemisphere

Winter SolsticeSouthern Hemisphere

Winter Solstice Northern Hemisphere

Summer Solstice Southern Hemisphere

• Climates are a product of precipitation, temperature, latitude, and elevation

• Biomes– Terrestrial ecosystems categorized by dominant types of

natural vegetation

• Major Climate Types– Ice Cap, Tundra & Subarctic– Desert & Semiarid / Steppe– Tropical Rain Forest & Tropical Savanna– Marine West Coast– Mediterranean– Humid Subtropical & Humid Continental– Undifferentiated Highland Climate

2.2.4 Climate and Vegetation Types

World Climate Types

World Biomes

Ice Cap BiomeBritish Columbia, Canada

The ice cap biome is devoid of vegetation, except in very few spots where enough ice or snow melts in the summer to allow tundra vegetation to grow.

TundraNorthern Norway

Tundra vegetation is composed of mosses, lichens,shrubs, dwarfed trees, and some grasses.

Coniferous ForestBritish Columbia, Canada

Needleleaf evergreen coniferous trees can stand long periods when the ground is frozen, depriving them of moisture. Coniferous forests occupy large areas of subarctic climate.

Desert ShrubSinai Peninsula, Egypt

Desert shrub vegetation is often foundonly in dry riverbeds in arid climates.

SteppeEastern Turkey

The steppe biome is composed mainly of short grassesand is also referred to as temperate grassland.

Tropical Rain ForestDominica, West Indies

The tropical rain forest climate is rainy and occurs at low latitudes.Heat and moisture are almost always present in the biome.

Tropical Deciduous ForestWestern India

The tropical deciduous forest is found in tropical areas with a dry season that still has enough moisture for tree growth. Note the Asiatic lions in the photo.

Scrub and Thorn ForestNorthern Zimbabwe

The tropical deciduous forest thins out tolow, sparse scrub and thorn forest in drier areas.

SavannaSouthern Kenya

Savanna vegetation, which has taller grasses than the steppe, occurs inareas of greater overall rainfall and more pronounced wet and dry seasons.

Mediterranean Scrub ForestSouthern California, USA

The Mediterranean climate is characterized by rainless summerscontrasted with cyclonic or orographic precipitation in the winter.

Temperate Mixed ForestSouthern Missouri, USA

The mixed forest is a transitional area where both needleleafand broadleaf trees are present and compete with each other.

Undifferentiated Highland VegetationSan Juan Mountains, Colorado, USA

Undifferentiated highland climates have a range of conditions based on elevation and exposure to wind and sun. The numerous biomes are impossible to map on a small scale.

• Biological Diversity– Number of plant and animal species present and the

variety of genetic materials these organisms contain– Most diverse biome is the tropical rain forest

• Struggling to Protect Biodiversity– Human removal of rain forests and natural ecosystems

depletes biodiversity– Controversy of the Green Revolution

• On one hand, puts more food on the global table• But may render crops more vulnerable to pests and diseases

– Establishment of National Parks and Protected Areas– Conservation International’s “Biodiversity Hot Spots”

2.3.1 The Importance of Biodiversity

World Biodiversity Hot Spots

34 Priority Regions Identifiedby Conservation International

• Water comprises about 71% of world’s surface

• Life on earth would not be possible without the resources of the Hydrosphere:– Oceans– Freshwater Sources

2.4 The World’s Oceans

• Oceans have the largest role in the hydrologic cycle– Seawater is converted into usable freshwater precipitation

• Oceans are a large source of food for humans– 15 percent of world’s population relies primarily on fish

as their source of protein

• They provide energy & raw materials for human use• They play important roles in trade and commerce

2.4.1 Why Should We Care About Oceans?

Tsukuji Fish Market Tokyo, Japan

Percentage of Ocean Fish Species “Collapsed”

• Although governments have been doing more in recent years to protect the earth’s biodiversity, atmospheric changes have profound impacts on natural systems

• These atmospheric changes are largely attributable to human activities

2.5 Global Environmental Change

• Human activities are responsible for a documented warming of the earth’s surface– Intergovernmental Panel on Climate Change

• 2007 report concluded that global warming is “unequivocal”

• Global Warming– Global mean temperature has increased 1.4 degrees F

since late 19th century

– Result of human production of greenhouse gases, such as Carbon Dioxide

2.5.1 Climatic Change

Carbon Dioxide vs. Mean Global Temperature

• Concept established in 1827 by French mathematician Jean-Baptiste Fourier– Fourier noted that the earth’s atmosphere acts like the

transparent glass cover of a greenhouse, allowing visible sunlight to pass through, and trapping some of the heat

– In our atmosphere, naturally occurring greenhouse gases make earth habitable by trapping heat from sunlight

– Concern over global warming focuses on human-derived sources of greenhouse gases, which trap abnormalamounts of heat

– Particularly problematic are human-produced methane, nitrous-oxide, and chlorofluorocarbons (CFCs)

2.5.2 The Greenhouse Effect

The Greenhouse Effect

• Effects of Global Warming on the Earth– Increase in global temperatures– More precipitation overall,

but also more pronounced drought– Pronounced warming in the polar regions– Shifting biomes, with species extinction– Rising sea levels– Geopolitical instability

2.5.3 The Effects of Global Warming

Ice-Free North Pole

• Is the damage irreversible?

• Some scientists urge dramatic steps be taken to mitigate global warming:– Negotiate and implement international treaties to

reduce greenhouse gas emissions• Montreal Protocol

– Cut emissions through market-based incentives– Increase carbon sequestration

2.5.4 Global Climate Change: What Can Be Done?