Exploring Geography

CHAPTER 1

Section 2

• Changes Within the Earth– Objectives:

• Describe both the internal and external structures of the Earth.

• Explain how forces inside the earth create and change landforms.

• Summarize the main ideas of plate tectonic theory.

Geology- the study of the earth’s physical

structure and history.

Vocabulary

• Key Terms:– Core– Mantle– Crust– Continents– Relief– Lava– Fold– Faults– Plate Tectonics– Continental Drift Theory– Ring of Fire

Changes Within the Earth

The Earth’s Structure

Internal Forces

Geologic History

Fig. 5.1

Plumbing System of a Volcano

Ejecta ash

• volcanic bombs

• volcanic tuff

• volcanic breccias

• pyroclastic flow (look out!)

Escaping a Pyroclastic Flow at

Mount Unzen, Japan, 1991

Shield Volcano

Fig. 5.10

Fig. 5.12

Cinder Cone

Fig. 5.14

Composite Volcano

Emil Muench/Photo Researchers

Before May, 1980

David Weintraub/Photo Researchers

After May, 1980

fissure eruption

1971 Fissure Eruption, Kilauea, Hawaii

Plate Tectonics:

the unifying theory

Plate Tectonics:The Unifying Theory

Peter W. Sloss, NOAA-NESDIS-NGDC

Fig. 20.1

“Fit” of the Continents

Pangaea 250 Million Years Ago

Fig.21.1

Relative Motion of the Plates

Relative Velocity and Direction of Plate Movement

Fig. 20.12Data from C. Demets, R.G> Gordon, D.F. Argus, and S. Sten, Model Nuvel-1, 1990

Fig. 20.11

Age of Seafloor Crust

R. Dietmar Muller, 1997

Types of plate Types of plate boundariesboundaries

• divergent: mid-ocean ridges

• convergent: collision zones

volcanic arcs

• strike-slip: San Andreas fault

Divergent Divergent boundariesboundaries

Two types: Examples:

Continent-Continent East African

Rift

Ocean–Ocean Mid-Atlantic

Ridge

Continental-Continental Divergent plate boundary

East African Rift Valley

Inception of Rifting Within a Continent

Fig. 20.4b

Cooling and subsidence of rifted margin allows sediments to be

deposited

Fig. 20.17b

Fig. 20.5a

Nile Delta

Gulf ofSuez

Gulf of‘Aqaba

Red Sea

Earth Satellite Corp.

Oceanic-Oceanic Divergent Plate Boundary

Mid-Atlantic Ridge

Fig. 20.4a

Rifting and Seafloor

Spreading Along the

Mid-Atlantic Ridge

Peter W. Sloss, NOAA-NESDIS-NGDC

Rifting and Seafloor Spreading

Fig. 20.4a

Convergent Convergent boundariesboundaries

Three types: Examples:

ocean–ocean Japan

ocean–continent Andes

continent–continent Himalaya

Oceanic-Oceanic Convergent Plate Boundary

Japan

Fig. 20.6b

Ocean–Ocean Subduction Zone

Fig. 20.18

Parts of an Ocean–Ocean Convergent Plate Boundary

Oceanic-Continental Convergent Plate Boundary

Andes Mountains

Fig. 20.6a

Ocean-ContinentSubduction Zone

Fig. 20.19

Parts of an Ocean–ContinentConvergent Plate Boundary

Continental-Continental Convergent Plate Boundary

India & Asia

Fig. 20.6c

Continent-Continent Collision

Fig. 20.20b

Continent– Continent Collision

Continent–Continent Convergent Boundary

Fig. 20.d

Indian plate subducts beneath Eurasian plate

Fig.21.6a

60 million years ago

Indian subcontinent collides with Tibet

Fig.21.6b

40–60 million years ago

Main boundary fault develops

Fig.21.6d10–20 million years ago

Transform Plate Boundary

San Andreas Fault

Fig. 20.5b

The Gulf of California Formed by

Rifting of Baja California

from Mainland Mexico

Worldsat International/Photo Researchers

Examples of Plate Boundaries

Fig. 20.8a,b

O-Oconvergent

O-Odivergent

O-Cconvergent

O-Cconvergent

O-Odivergent

C-Cdivergent

O-Odivergent