Earthquakes, Volcanoes, and Tsunamis: Projects and Principles for Beginning Geologists
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The Secrets of the Earth e all live on the surface of the earth but did you ever wonder what goes on beneath the surface deep inside the earth deeper than the deep est mine No human being has ever been down there but earth scientists have been able to learn a lot about what it's made of and what goes on inside the big sphere on which we live And at the same time their discoveries have helped to explain much of the mystery of how earthquakes happen and volca noes erupt Imagine that the earth is like an apple or a peach
and consists of a skin a meaty part and a core or pit The core of the earth is solid metal iron and nick el surrounded by hot liquid metals The meat of the earth the mantle is a hot somewhat soupy mass of melted rock called magma The skin of the planet is its crust the hard surface of the earth on which we live Crust Mantle Liquid core Solid core 1 250 km 775 mi 2 200 km 2 900 km 1 364 mi 1798 mi The crust is not equally thick all around the earth It is as deep as 40 kilometers 25 miles under the surface of the continents and as thin as 5 kilometers 3 miles under the ocean
Until recently the crust was assumed to be solid rock but discoveries have shown instead that it is cracked into separate sections called tectonic plates Some of them are so large that they determine the boundaries of entire continents or oceans one of the plates supports all of the United States and the whole Pacific Ocean sits on another Other sections are smaller supporting only part of a continent or a small group of islands like the plate under the Car
