Lecture_8

Lecture_8 - Earth and the Terrestrial Worlds Earth as a...

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1 Earth and the Terrestrial Worlds Mercury craters smooth plains, cliffs Venus volcanoes few craters Mars some craters volcanoes riverbeds? Earth volcanoes craters mountains riverbeds Our Goals for Learning • Why is Earth geologically active? • What processes shape Earth’s surface? • How does Earth’s atmosphere affect the planet? Earth as a Planet Earth as a Planet Why is Earth geologically active? Why is Earth geologically active? Short answer : the Earth is big enough to still have a hot interior. So what do we know about the interior of the Earth and why is it hot? Internal Structure, by density Internal Structure, by density LITHOSPHERE
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2 Internal structure, by rock strength Internal structure, by rock strength The lithosphere is the cool rigid rock that forms a planet’s outer layer: the crust and some of the mantle . The lithosphere “floats” on the lower layers which are soft and molten. Internal Structure of the Terrestrial Planets Sources of Internal Heat Sources of Internal Heat 1) Gravitational potential energy of accreting planetesimals 2) Differentiation Heavier elements sink 3) Radioactivity Emitted particles carry energy Differentiation Differentiation • Layers ordered by density • Highest density on the bottom – Earth’s core is very dense • Gravity sorts materials by density. – e.g. oil and water don’t mix because of very different densities • Differentiation converts gravitational potential energy to heat .
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3 Heat Drives Geological Activity Heat Drives Geological Activity Convection: hot molten rock rises, cooler molten rock falls. One cycle takes 100 million years on Earth. A large planet… • Is still warm inside • Has a convecting mantle • Has a thinner, weaker lithosphere • Has molten rock nearer the surface All of which makes it more geologically active Examples: Earth and Venus, but not Mars (too small) Planetary magnetic fields are important Compare a bar magnet, a coil of wire with a current flowing through it, and the Earth’s magnetic field – all similar. Moving charged particles create magnetic fields,
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This note was uploaded on 02/20/2012 for the course ASTRO 3 taught by Professor Mclean during the Spring '11 term at UCLA.

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Lecture_8 - Earth and the Terrestrial Worlds Earth as a...

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