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.

- the study of the earth’s physical structure and history. Geology - the study of the earth’s physical structure and history.

Vocabulary BEFORE AFTER Key Terms: Core Mantle Crust Continents Relief Lava Fold Faults Plate Tectonics Continental Drift Theory Ring of Fire BEFORE AFTER

Changes Within the Earth The Earth’s Structure Internal Forces Geologic History

Plumbing System of a Volcano Fig. 5.1

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

Cinder Cone Fig. 5.12

Composite Volcano Fig. 5.14

Before May, 1980 Emil Muench/Photo Researchers

After May, 1980 David Weintraub/Photo Researchers

fissure eruption

1971 Fissure Eruption, Kilauea, Hawaii

Plate Tectonics: the unifying theory

Plate Tectonics: The Unifying Theory Peter W. Sloss, NOAA-NESDIS-NGDC

“Fit” of the Continents Fig. 20.1

Pangaea 250 Million Years Ago Fig.21.1

Relative Motion of the Plates

Relative Velocity and Direction of Plate Movement Fig. 20.12 Data from C. Demets, R.G> Gordon, D.F. Argus, and S. Sten, Model Nuvel-1, 1990

Age of Seafloor Crust Fig. 20.11 R. Dietmar Muller, 1997

Types of plate boundaries • divergent: mid-ocean ridges • convergent: collision zones volcanic arcs • strike-slip: San Andreas fault

Divergent boundaries 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

Gulf of ‘Aqaba Gulf of Suez Nile Delta Gulf of ‘Aqaba Gulf of Suez Red Sea Fig. 20.5a Earth Satellite Corp.

Oceanic-Oceanic Divergent Plate Boundary Mid-Atlantic Ridge

Rifting and Seafloor Spreading Along the Mid-Atlantic Ridge Fig. 20.4a Peter W. Sloss, NOAA-NESDIS-NGDC

Rifting and Seafloor Spreading Fig. 20.4a

Convergent boundaries Three types: Examples: ocean–ocean Japan ocean–continent Andes continent–continent Himalaya

Oceanic-Oceanic Convergent Plate Boundary Japan

Ocean–Ocean Subduction Zone Fig. 20.6b

Parts of an Ocean–Ocean Convergent Plate Boundary Fig. 20.18

Oceanic-Continental Convergent Plate Boundary Andes Mountains

Ocean-Continent Subduction Zone Fig. 20.6a

Parts of an Ocean–Continent Convergent Plate Boundary Fig. 20.19

Continental-Continental Convergent Plate Boundary India & Asia

Continent-Continent Collision Fig. 20.6c

Continent– Continent Collision Fig. 20.20b

Continent–Continent Convergent Boundary Fig. 20.d

Indian plate subducts beneath Eurasian plate 60 million years ago Fig.21.6a

Indian subcontinent collides with Tibet 40–60 million years ago Fig.21.6b

Main boundary fault develops 10–20 million years ago Fig.21.6d

Transform Plate Boundary San Andreas Fault

The Gulf of California Formed by Rifting of Baja California from Mainland Mexico Fig. 20.5b Worldsat International/Photo Researchers

Examples of Plate Boundaries O-C convergent O-O divergent C-C divergent O-O divergent O-O convergent O-O divergent O-C convergent Fig. 20.8a,b