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Transcript
Chapter 3 The Dynamic Earth The Earth as a System Earth is an integrated system that consists of 4 parts. – Rock, air, water, living things Four interactive parts – Geosphere (rock) – Atmosphere (air) – Hydrosphere (water) – Biosphere (living things) Geosphere Solid part of the earth (rock, soils, and sediments) Most of geosphere located in earth’s interior. The Atmosphere Mixture of gases that makes up all of the air we breathe. The Hydrosphere Makes up all of the water on or near the earth’s surface. Much of the water is in the oceans. Water is also found in atmosphere, on land, and in soil. The Biosphere Made up of parts of the geosphere, atmosphere and hydrosphere. Part of the earth where life exists. Extends from 9km above the earth’s surface down to the bottom of the ocean. Discovering Earth’s Interior Scientists use seismic waves to learn about Earth’s interior. Seismic Waves: same waves that travel through earth’s interior during an earthquake. The Composition of the Earth Earth: divided into 3 layers based on the composition on each layer – Crust, Mantle, Core Made of progressively denser materials toward the center of the earth. The Crust Made almost entirely of light elements. Makes up less than 1% of the planet’s mass. Thinnest layer. 5km to 70km thick The Mantle Layer beneath crust. Makes up 64% of the mass of earth. Approx. 2,900 km thick. (1,802 miles) Made of rocks of medium density. The Core Composed of the densest elements. Radius of approx. 3400 km. The Structure of the Earth Earth can be divided into five layers based on physical properties of each layer. 1. Lithosphere: outer layer; cool, rigid, 15km-300km thick. Includes crust and uppermost layer of mantle. Divided into tectonic plates. 2. Asthenosphere: beneath the lithosphere. Made of rock that flows very slowly and allows tectonic plates to move on top of it. 3. Mesosphere: lower part of the mantle. 4. Outer core: made of liquid nickel and iron. 5. Inner core: sphere of solid nickel and iron. Plate Tectonics Lithosphere is divided into tectonic plates. Plates glide across the underlying asthenosphere. Major tectonic plates: Pacific, North American, Cocos, Nazca, South American, Eurasian, Indian, Australian, Antarctic Plate Boundaries Much of the geologic activity at surface of earth takes place at boundaries between tectonic plates. Plate Tectonics and Mountain Building When tectonic plates collide, crust becomes thicker and eventually forms mountain ranges. Earthquakes Fault: break in earth’s crust along which blocks of the crust slide relative to one another. Majority of earthquakes take place at or near tectonic plate boundaries. When rocks that are under stress break along a fault, ground vibrations are set off. -Richter scale: used to quantify the amount of energy released by a earthquake. Volcanoes Mountain built from magma. Often located near tectonic boundaries where plates are either colliding or separating from one another. May occur on land or under sea. Local Effects of Volcanic Eruptions Volcanic ash can mix with water and cause mudflows. Entire cities can be engulfed. Global Effects of Volcanic Eruptions Can change earth’s climate. Can reduce sunlight exposure. Can reduce global temperature. Erosion Removal and transport of surface material. Can be either caused by water or wind