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PHYSICAL PROCESSES AND WORLD REGIONS

Chapter 2

Objectives

This chapter will enable you to:

Understand the tectonic forces behind some of the world’s major landforms and natural hazards

Recognize consistent global patterns in the distribution of vegetation types and climates

Identify the natural areas most threatened by human activity and explain how natural habitat loss may endanger human welfare

Objectives (cont’d.)

Appreciate the important roles of the world’s oceans

Describe the potential impacts of global climate change and international efforts to prevent them

Four Spheres of Earth’s Habitable Environment

Lithosphere

Hydrosphere

Atmosphere

Biosphere – “ecosphere”

Geologic PrPlate Tectonics

Continental drift

Idea proposed by Alfred Wegener, 1912

Continents once joined as supercontinent called “Pangaea” but they “drifted apart” over time

Earth’s lithosphere is made up of several plates that move in various directions

Plate Tectonics (cont’d.)

Seafloor spreading

Process of two plates moving away from each other

Few impacts on people where plates diverge

Huge consequences where they converge

Converging plates

Trigger some of the planet’s greatest natural hazards

Subduction (one plate “dives” below another)

Plate Tectonics (cont’d.)

Seismic activity

Refers to Earth vibrations when plates move past one another

Earthquakes

Strength measured on the Richter Scale

Tsunamis

Volcanism

Movement of molten earth material

Generally occurs along or near subduction zones

Tectonic Plates

Figure 2.1 Major tectonic plates and their general direction of 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 (well below sea level at the Dead Sea of Israel and Jordan, for example) or the emergence of new crust on the ocean floor (in the middle of the Atlantic Ocean, for example). The yellow ring points to the rough outline of the “Ring of Fire.”

Source: Adapted from NASA, “Global Tectonic Activity Map of the Earth,” DTAM-1, 2002

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

Earth’s Interior and Its Forces

Figure 2.2 The Earth is composed of core, mantle, and crust. Dynamic forces within the core and mantle have major effects on what happens in the crust and on the surface, including impressive but dangerous events like earthquakes and volcanoes. These forces create many of Earth’s landforms. The yellow arrows illustrate how the lithosphere is “recycled.”

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

Precipitation

Precipitation and temperature

Key variables in weather and climate

Water is essential for life on Earth

Precipitation – results from processes that cool the air to release moisture

Types include:

Rain

Snow

Sleet

Hail

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

World Precipitation

Figure 2.3 World precipitation map. Is this, as some authorities say, the most important of all world maps?

Climate

Climates – product of precipitation, temperature, latitude, and elevation

Major Köppen climate types

Ice Cap, tundra & subarctic

Desert & semiarid / steppe

Tropical rain forest & tropical savanna

Marine west cast

Mediterranean

Humid subtropical & humid continental

Undifferentiated highland climate

World Climate Types

Figure 2.4 World climates.

World Biomes

Figure 2.5 World biomes (natural vegetation) map.

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.

Ice Cap

Figure 2.6o Ice cap, western Svalbard (Spitsbergen), Norway.

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

Tundra

Figure 2.6n Tundra, northern Norway.

Desert shrub vegetation is often found only in dry riverbeds in arid climates.

Desert Shrubland

Figure 2.6h Desert shrubland annuals in full glory following winter rains, Anza Borrego Desert State Park, southern California.

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

Tropical Moist Broadleaf Forest

Figure 2.6a Tropical moist broadleaf forest (tropical rain forest) at the ancient Maya site of Tikal, northern Guatemala.

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

Tropical Grassland (Savanna)

Figure 2.6i Tropical grassland (savanna), southern Kenya.

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

Mediterranean Scrub

Figure 2.6g Mediterranean scrub and woodland of California’s coastal range. The Calaveras Fault lies at the boundary of San Jose’s eastern suburbs with the hills beyond.

Temperate Mixed Forest

Figure 2.6b Temperate broadleaf and mixed forest, northwest Florida.

Undifferentiated Highland Vegetation

Figure 2.6p Undifferentiated highland vegetation, San Juan Mountains, Colorado, United States. Note the timberline above which trees do not grow. Here, biomes change with elevation, and so the vegetation climate types have to be characterized as “undifferentiated” on small-scale maps.

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

The Importance of Biodiversity (cont’d.)

Struggling to protect biodiversity

Human removal of rain forests and natural ecosystems deplete biodiversity

Controversy of the green revolution

Establishment of national parks and protected areas

Conservation International’s “Biodiversity Hot Spots”

34 Priority Regions Identified by Conservation International

World Biodiversity Hotspots

Figure 2.8 World biodiversity hotspots as recognized by Conservation International.

Why Should We Care About Oceans?

70% of the world’s surface is water

Oceans: largest role in hydrologic cycle

Seawater is converted into usable freshwater through evaporation and 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

Why Should We Care About Oceans? (cont’d.)

The oceans provide energy & raw materials for human use

The oceans play important roles in trade and commerce

90% of global trade is seaborne

Commercial Shipping Routes

Figure 2.11 World commercial shipping routes, as mapped by the National Center for Ecological Analysis and Synthesis. Over thirty-three hundred commercial and research vessels were tracked for a year to develop this map showing where human activity on the oceans is highest.

Global Climate Change

Human activities are responsible for a documented warming of Earth’s surface

Intergovernmental Panel on Climate Change (IPCC)

United Nations-sponsored panel

Made up of 2,500 atmospheric scientists from 130+ countries

2014 report concluded that global warming is “unequivocal”

Global Climate Change (cont’d.)

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 Concentration

Figure 2.12 Industrialization, the burning of tropical forests and other factors have produced a steady increase in carbon dioxide emissions. Most scientists believe that these increased emissions explain the corresponding steady increase in the global mean temperature.

The Greenhouse Effect

Concept established in 1827 by French mathematician Jean-Baptiste Fourier

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

The Greenhouse Effect (cont’d.)

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

Greatest source of concern is the release human-induced carbon dioxide into atmosphere

Other problematic human-produced greenhouse gases are methane, nitrous-oxide, and chlorofluorocarbons (CFCs)

The Greenhouse Effect (cont’d.)

Figure 2.13 The greenhouse effect. Some of the solar energy radiated as heat (infrared radiation) from the Earth’s surface escapes into space, while greenhouse gases trap the rest. Naturally occurring greenhouse gases make the Earth habitable, but carbon dioxide and greenhouse gases emitted by human activities accentuate the greenhouse effect, making the planet unnaturally warmer.

The Effects of Global Warming

Increase in global temperatures by 2°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

Global Patterns of Impacts

Figure 2.14 Global patterns of impacts in recent decades attributed to climate change. Impacts are shown at a range of geographic scales. Symbols indicate categories of attributed impacts, the relative contribution of climate change (major or minor) to the observed impact, and confidence in attribution.

What Can We Do About Global Climate Change?

Approaches to confronting climate change

Mitigation

Montreal Protocol – reduce CFCs

Cut emissions through market-based incentives

Clean development mechanism

Joint implementation

Cap and trade

Increase Carbon Sequestration

Natural capture and long-term storage

Forests, farmlands, oceans

Reducing Emissions from Deforestation and Forest Degradation (REDD)

The Kyoto Protocol and Beyond

1992 treaty: United Nations Framework Convention on Climate Change

1997 Kyoto Protocol

Emission reduction targets

Extended until 2020