Chapter 1

Introduction to Physical Geology

Index

Geology

• Geology – The scientific study of the earth.

• Physical Geology

• Physical Geology – A large division of geology concerned with earth materials, changes of

the surface and interior of the earth, and the forces that cause those changes.

The Earth’s Interior

• Crust – The outer layer of rock, forming a thin skin over the earth’s surface.

• Mantle – A thick shell of rock that separates the earth’s crust above from the core

below.

• Core – The central zone of the earth.

More Layers

• Lithosphere – The rigid outer shell of the earth, 70 to 125 or more kilometers thick.

• Asthenosphere – A region of the earth’s outer shell beneath the lithosphere. The asthenosphere is of indeterminate thickness and behaves plastically.

• Fig 1.8

Why understand geology?

• Helps us:

• Avoid Geologic Hazards• Supplies Things We Need• To Protect the Environment• To Understand Our Surroundings

The Theory of Plate Tectonics

• Plate Tectonics – A theory that the earth’s surface is divided into a few large, thick plates that are slowly moving and changing in size.

Geologic activities occur at the plate boundaries

• Tectonic Forces – Forces generated from within the earth that result in uplift, movement, or

deformation of part of the earth’s crust.• Fig. 1.10

Plate Boundaries

• Divergent Boundaries

• Transform Boundaries

• Convergent Boundaries

Divergent Boundaries

~ Boundary separating two plates moving away from each other.

• Most divergent boundaries coincide with the crests of submarine mountain ranges, called mid-oceanic ridges.

• Fig. 1.11

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Fig. 1.11

• Pg. 17

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Transform Boundary

~ Boundary between two plates that are sliding past each other.

• An example is the San Andreas fault in California.

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Convergent Boundary

• ~Boundary between two plates that are moving toward each other.

• If one plate is capped by oceanic crust and the other by continental crust, the less dense, more buoyant continental plate will override the denser, oceanic plate. The oceanic plate sinks along what is known as a subduction zone, a zone where an oceanic plate descends into the mantle beneath an overriding plate.

• Fig. 1.12

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Fig. 1.12

• Pg. 18

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Vocabulary

• Magma – Molten rock, usually mostly silica. The liquid may contain dissolved gases as well as some solid minerals.

• Erosion – The physical removal of rock by an agent such as running water, glacial ice, or wind.

• Equilibrium – Material is in equilibrium if it is adjusted to the physical and chemical conditions of its environment so that it does not change or alter with time.

• Sediment – Loose, solid particles that can originate by (1) weathering and erosion of preexisting rocks, (2) chemical precipitation from solution, usually in water, and (3) secretion by organisms

• Fig. 1.13

Geologic Time

• (put picture of Table 1.1 on pg. 22)

Put picture of page 19-20

Back to the Beginning

Fig. 1.8

• Fig. 1.8 on pg. 15

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Fig. 1.10

• Pg. 16

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Fig. 1.13

• Pg. 21

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