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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