PHYSICAL PROCESSES AND WORLD REGIONS

Chapter 2

Four Spheres of Earth’s Habitable Environment

Lithosphere Earth’s outer “rind” of rock Varies in thickness from about 50 to 125 miles Made up of large sections of rock called plates A work in progress, providing opportunities and threats

Hydrosphere Comprised of the Earth’s water features

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

Biosphere (Ecosphere) Global ecological system where relationships play out

among the lithosphere, hydrosphere, and atmosphere

2.1.1 Plate Tectonics

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 2 plates moving away from each other Few impacts on people

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

2.1.1 Plate Tectonics (continued)

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

Earthquakes Strength 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 Magnitude 9.0 Japan, 2011

Tsunamis (Tidal Waves) Volcanism

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

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

Generalized cross section of the Earth, showing its main concentric layers and the process by which its lithosphere is recycled.

2.2 Patterns of Climate and Vegetation

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

2.2.1 Precipitation

Precipitation and Temperature are the key variables in weather and climate Water is essential for life on Earth

Precipitation Result of processes that cool the air to release

moisture Types of precipitation include:

Rain Snow Sleet Hail

World Precipitation Map

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

2.2.2 Climate and Vegetation Types

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

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.

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 in

areas 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 ForestCentral 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.

2.2.3 The Importance of Biodiversity

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”

World Biodiversity Hot Spots

34 Priority Regions Identified by Conservation International

2.4 The World’s Oceans

Water comprises about 71% of world’s surface Life on earth would not be possible without the

resources of the Hydrosphere: Oceans Freshwater Sources (e.g., lakes, rivers)

The World Commission on Water projects that by 2025, half of the world’s population will live under conditions of severe water stress

2.4.1 Why Should We Care About Oceans?

It’s a watery world 70% of the world’s surface is comprised of water Oceans have the largest role in the hydrologic cycle

Seawater is converted into usable freshwater precipitation

The oceans feed us 15% of the world’s population relies primarily on fish

as their source of protein Global demand for seafood has increased 40% since 1980

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

90% of global trade is seaborne

Pike Street Market Seattle, Washington

2.5 Global Environment Change

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

2.5.1 Climatic Change

Human activities are responsible for a documented warming of the earth’s surface Intergovernmental Panel on Climate Change (IPCC)

United Nations-sponsored panel Made up of 2,500 atmospheric scientists from 130+ countries 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

Carbon Dioxide vs. Mean Global Temperature

2.5.2 The Greenhouse Effect

Concept established in 1827 by French mathematicianJean-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)

The Greenhouse Effect

2.5.3 The Effects of Global Warming

Effects of Global Warming on the Earth Increase in global temperatures by 3°F to 7°F by 2100 More precipitation overall,

but also more pronounced drought Pronounced warming in the polar regions Shifting biomes, with species extinction and

agricultural changes Rising sea levels Geopolitical instability

Ice-Free North Pole

2.5.4 Global Climate Change:What Can Be Done?

China and the U.S. account for roughly 40% of the entire global emissions output

Approaches to confronting climate change Mitigation

Switching from coal to cleaner fossil fuels to produce electricity

Reducing energy consumption Removing greenhouses from the atmosphere by boosting

photosynthesis Adaptation

Cope with and reduce the unavoidable impacts of climate change

Building sea walls to prevent flooding due to rising sea levels Relocating people from flood-prone areas to higher ground Developing crop varieties that are more suited to expected

changes in temperature and precipitation

2.5.4 Global Climate Change:What Can Be Done? (continued)

Approaches to mitigating climate change Negotiate and implement international treaties to reduce

greenhouse gas emissions Montreal Protocol

Signed by 37 countries in the late 1980s Production of CFCs worldwide reduced in phases to zero by 2010 Resulted in reduction of stratospheric ozone “holes”

Cut emissions through market-based incentives Cap-and-Trade or Emission-Trading

Increase carbon sequestration Natural capture and long-term storage of carbon in so-called

carbon sinks (forests, farmlands, and oceans), so that the build-up of carbon dioxide in the atmosphere will reduce or slow.