Chapter 11:The Dynamic Planet • The Pace of Change A. The Geologic Time Scale II. Earth’s Structure and Internal Energy A. The Earth’s Core B. The Earth’s Mantle C. The Earth’s Crust III. The Geologic Cycle A. Defined B. Types of Rock IV. Plate Tectonics
Pace of Change A. Geologic Time Scale Figure 8.1
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
II. Earth’s Structure and Internal Energy • Earth’s Core • Inner 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 surface. • 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 Mantle • Begins 2900 km (1800 miles deep) up to 200 km beneath Earth’s surface • Represents about 80% of Earth’s total volume • Dominated by iron, magnesium, and silicates • 670 km (415 miles) deep is where the upper and lower mantle separate.
II. Earth’s Structure and Internal Energy C. Earth’s Crust • Begins 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)
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.
III. The Geologic Cycle Geologic Cycle: Refers to the vast cycling of rocks and minerals that occurs in the lithosphere. It encompasses the hydrologic cycle, the tectonic cycle, and the rock cycle. • Factors that fuel the geologic cycle: • Earth’s internal heat • Solar energy from space • Earth’s gravity
III. The Geologic Cycle A. Rock Cycle The 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. • Igneous: Rocks formed by the solidification of magma. (granite, basalt, rhyolite) • Sedimentary: Rocks formed by the alteration and compression of old rock debris or organic sediments (sandstone, shale, limestone) • Metamorphic: Rocks formed by alteration of existing rocks by intense heat or pressure. (marble, quartz, slate)
III. The Geologic Cycle A. The Rock Cycle Figure 11.6
III. The Geologic Cycle Igneous Rock Types
IV. Plate Tectonics Continental landmasses migrated to their current position and 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)
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 A. Crustal Movements Sea floor spreading builds the mid-ocean ridges. * Note the subduction of oceanic crust underneath the continental crust. Figure 8.13
IV. Plate Tectonics C. Continents Adrift Figure 8.16
IV. Plate Tectonics D. Earth’s Major Plates • Boundary Types: • Divergent • Convergent • Transform Figure 8.17