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Chapter 8:The Dynamic Planet

I. The Pace of ChangeA. The Geologic Time Scale

II. Earth’s Structure and Internal EnergyA. The Earth’s CoreB. The Earth’s MantleC. The Earth’s Crust

III. The Geologic CycleA. DefinedB. Types of Rock

IV. Plate Tectonics

I. Pace of ChangeA. Geologic Time Scale

Figure 8.1

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II. Earth’s Structure and Internal Energy

Earth is estimated to be around 4.6 billion years old.

Earth’s continental crust formed 4.0 billion years ago.

Earths’ interior is sorted into concentric layers, each one distinct in either chemical composition or temperature.

II. Earth’s Structure and Internal Energy

Figure 8.2

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II. Earth’s Structure and Internal Energy

A.Earth’s Core

Inner core: solid iron 5150 kmInner core: solid iron, 5150 km beneath the Earth’s surface

Outer core: molten metallic iron and lighter in density than the inner core, extends 2900 –5150 km beneath Earth’s surfacesurface.

Outer core generates 90% of Earth’s magnetic field that protects us from solar wind.

II. Earth’s Structure and Internal Energy

B. Earth’s MantleB i 2900 k (1800Begins 2900 km (1800 miles deep) up to 200 km beneath Earth’s surfaceRepresents about 80% of Earth’s total volumeDominated by iron, magnesium, and silicatesg ,670 km (415 miles) deep is where the upper and lower mantle separate.

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II. Earth’s Structure and Internal Energy

C. Earth’s CrustBegins about 200 km beneath Earth’s surface

Composed of the lithosphere (includes continental and oceanic crust)

The asthenosphere lies directly beneath the lithosphere

Continental crust is granite, very low density (2.7g/cm3).

Oceanic crust is basalt higher density (3 0g/cm3)Oceanic crust is basalt, higher density (3.0g/cm )

II. Earth’s Structure and Internal Energy

• Structure of the Earth's crust and top most layer of the upper mantle.

• Beneath the lithosphere is the asthenosphere. This layer, which is also part of the upper mantle, extends to a depth of about 200 kilometers.

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III. The Geologic Cycle

Geologic Cycle: Refers to the vast cycling of rocks d i l th t i th lith h Itand minerals that occurs in the lithosphere. It

encompasses the hydrologic cycle, the tectonic cycle, and the rock cycle.

Factors that fuel the geologic cycle:1. Earth’s internal heat2. Solar energy from space3. Earth’s gravity

III. The Geologic Cycle

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III. The Geologic Cycle

A. Rock CycleThe rock cycle is a general model that describes how various geological processes create, modify, and influence rocks

III. The Geologic Cycle

Rock types are identified by the processes that form them.

I R k f d b th lidifi ti f1. Igneous: Rocks formed by the solidification of magma. (granite, basalt, rhyolite)

2. Sedimentary: Rocks formed by the alteration and compression of old rock debris or organic sediments (sandstone, shale, limestone)

3. Metamorphic: Rocks formed by alteration of existing rocks by intense heat or pressure. (marble, quartz, slate)

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III. The Geologic CycleA. The Rock Cycle

Figure 11.6

III. The Geologic CycleIgneous Rock Types

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Sedimentary Rock Types

Sedimentary Rock Types

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Metamorphic Rock Types

IV. Plate Tectonics

Continental landmasses migrated to their current position and continue to move about 2 4 inches per yearand continue to move about 2.4 inches per year.

Continental drift: Idea that the Earth’s landmasses have migrated over the past 225 million years from a supercontinent called Pangaea to the present configuration. (essentially plate tectonics)

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IV. Plate Tectonics

Mid-ocean ridges are the result of upwelling flows of magma from hot areas in the upper mantle and asthenosphere (possibly the lower mantle too).

IV. Plate Tectonics

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IV. Plate TectonicsA. Crustal Movements

Sea floor spreading builds p gthe mid-ocean ridges.

* Note the subduction of oceanic crust underneath the continental crust.

Figure 8.13

IV. Plate TectonicsA. Crustal Movements

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IV. Plate TectonicsB. Relative Age of the Oceanic Crust

Figure 8.15

IV. Plate TectonicsOceanic Trenches

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IV. Plate TectonicsC. Continents Adrift

Figure 8.16

IV. Plate TectonicsD. Earth’s Major Plates

Boundary Types:1 Di t1. Divergent2. Convergent3. Transform

Figure 8.17

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Figure 8.20