What Do Scientists Know About Earth’s Surface and Interior? Pages 71- 79, LS 2.4

1. What Do Scientists Know About Earth’s Surface and Interior?Pages 71- 79, LS 2.4

2. Earth’s Layers

3. What Are The Layers of the Earth? • Earth consists of three main layers – the crust, mantle and core. • Each layer has it’s own composition – the parts that make up the whole. • When a volcano erupts, material is ejected. Scientists examine these materials to learn about the materials that make up the layers of the Earth.

4. How Do Scientists Study Earth’s Interior? • The main tool scientists use to probe Earth’s interior is seismology. • Seismic waves change speed as they cross the boundary between two substances that differ in density. • Scientists learn about Earth’s interior by studying pieces of Earth’s interior that travel to the surface of the Earth during volcanic eruptions.

5. How Do Scientists Study Earth’s Interior? • Scientists also make inferences about Earth’s composition based upon what they know about the origin of our planet. • Analyzing the composition of meteorites provides evidence of Earth’s original composition. • Scientists can compare Earth’s original composition to the composition of the crust and upper mantle to see what is missing and then can make inferences about what is in the lower mantle and the core.

6. Earth’s Crust • Earth’s crust varies in thickness. • The thinnest parts of the crust are under the oceans. These parts are called oceanic crust. • The thickets parts of the crust are the continents. These parts are called continental crust. • For example, the crust under the ocean is only about 3 miles thick and the crust under the Himalayan Mountains is 47 miles thick. • Rocks making up the continental crust are less dense and oceanic crust is much more dense.

7. Earth’s Plates • The crust is broken into large pieces, called plates. • The edges of the plates are called plate boundaries. • Places where plates meet experience a lot of geological activity. • These plates move and shift, resulting in earthquakes volcanic eruptions, and changes in the topographic features of the Earth.

8. Earth’s Mantle • Mantle rock is made up of minerals that are denser, darker in color and have higher melting points than those in the curst. • The mantle is much hotter than the crust and is under tremendous pressure. • Compared to the crust, the mantle is huge-occupying about 70% of Earth’s volume compare to the 1% occupied by the crust.

9. Earth’s Layers • Earth’s outermost 62 miles of rock, which includes the crust and the uppermost part of the mantle, are rigid, brittle solids. This is called the lithosphere. (Litho = rock) • From 62 miles to about 217 miles, high temperatures and pressures make the rock more flexible. The rock is weak and easily deformed. This flexible part of earth, which includes the mantle, is called the asthenosphere. (astheno = weak/soft)

10. Earth’s Core • The core is metal, mostly consisting of iron and nickel. • The outer core is a layer of molten metal that flows very slowly • In the inner core, pressure and temperature act together to form a dense ball of solid metal. • Temperatures in the inner core reach 9032 degrees F. • Extreme pressure from the weight of the layers above squeezes the particle sof iron and nickel together so much that they cannot move.

11. Earth’s Layers Revisited