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Bell Questions 9/8/11 1. List three things that make Earth Unique. 2. List the three Compositional Zones of the Earth. Earth: A Unique Planet Earth Basics • Earth is the third planet from the sun. • Earth formed about 4.6 billion years ago • Made mostly of rock. • Approximately 70% of Earth’s surface is covered by the global ocean. • Earth is an oblate sphere, or a slightly flattened sphere. • Earth’s average diameter is 12,756 km. Earth’s Interior • Scientists use seismic waves to find out about Earth’s interior. • Seismic waves caused by earthquakes and explosions near surface. • P waves – through solids and liquids • S waves – through solids only Page 298 Earth’s Interior The diagram below shows the layers of Earth’s interior. Page 28 Compositional Zones 1. Crust the thin and solid outermost layer 2. Mantle the layer of rock that lies between Earth’s crust and core. The mantle is nearly 2,900 km thick. 3. Core the central part of Earth, composed mainly of nickel and iron whose radius is about 3,500 km. Structural Zones 1. lithosphere the solid, outer layer of Earth that consists of the crust and the rigid upper part of the mantle 2. asthenosphere the solid, plastic layer of the mantle beneath the lithosphere; flows very slowly 3. mesosphere the “middle sphere”; the strong, lower part of the mantle between the asthenosphere and the outer core Structural Zones (cont.) 4. Liquid outer core - below the mesosphere 5. Solid inner core – surrounded by the outer core and begins at a depth of 5,150 km. Earth’s Interior 1. What three compositional zones make up Earth’s interior? 2. Which compositional zone of Earth makes up almost two-thirds of the planet’s mass? 3. The asthenosphere floats on which structural zone? 4. What structural zones make up Earth’s interior? 5. Where is the Moho found? 6. The mantle is made up of what structural zones? Bell Questions 9/9/11 1. What are the five structural zones? 2. How do we know the outer core of the Earth is liquid? Earth as a Magnet • Earth’s magnetic field extends beyond the atmosphere and affects a region of space called the magnetosphere. • Motions within the liquid iron of Earth’s outer core produce electric currents that in turn create Earth’s magnetic field. Earth’s Gravity • Gravity is the force of attraction that exists between all matter in the universe. • The force of attraction between any two objects depends on the masses of the objects and the distance between the objects. The force of gravity acts between all objects If mass increases, the force of gravity increases If distance increases, the force of gravity decreases Earth’s Gravity Weight and Mass • Weight is a measure of the strength of the pull of gravity on an object. (Newton) • An object’s weight depends on its mass and its distance from Earth’s center. Weight and Location • More distance between center and surface of the earth at the equator so an object’s weight is about 0.3% less than at the poles.