Ch. 7 Plate Tectonics This is a satellite image of the San Francisco Bay area. The row of lakes below marks the line of the San Andreas fault, a crack in Earth's crust.

7.1 Inside the Earth Discover Activity Canisters with different items What is inside?

Can you dig down to the center? The deepest mine in the world, a gold mine in South Africa, reaches a depth of 3.8 kilometers. But it only scratches the surface.

Finding Indirect Evidence Geologist use an indirect method of studying Earth’s interior. Hanging a picture on a wall Geologists use seismic waves.

Finding Indirect Evidence Seismic waves - A vibration that travels through Earth carrying the energy released during an earthquake.

Finding Indirect Evidence Geologists record the seismic waves and study how they travel through Earth. The speed of these seismic waves and the paths they take reveal how the planet is put together. Using data from seismic waves, geologists have learned that Earth's interior is made up of several layers. Each layer surrounds the layers beneath it, much like the layers of an onion. Geologists record the seismic waves and study how they travel through Earth. The speed of these seismic waves and the paths they take reveal how the planet is put together. Using data from seismic waves, geologists have learned that Earth's interior is made up of several layers. Each layer surrounds the layers beneath it, much like the layers of an onion.

A Journey to the Center of the Earth Book written in 1864 Scientists knew nothing. Was the Earth hot, cold, solid, or hollow?

A Journey to the Center of the Earth

You would need a vehicle that could travel through solid rock. The vehicle would carry scientific instruments to record changes in temperature and pressure as you descend toward the center of Earth. You would need a vehicle that could travel through solid rock. The vehicle would carry scientific instruments to record changes in temperature and pressure as you descend toward the center of Earth.

Temperature As you start to tunnel beneath the surface, you might expect the rock around you to be cool. At first, the surrounding rock is cool. Then at about 20 meters down, your instruments report that the surrounding rock is getting warmer. For every 40 meters that you descend from that point, the temperature rises 1 Celsius degree. This rapid rise in temperature continues for several kilometers. After that, the temperature increases more slowly, but steadily. As you start to tunnel beneath the surface, you might expect the rock around you to be cool. At first, the surrounding rock is cool. Then at about 20 meters down, your instruments report that the surrounding rock is getting warmer. For every 40 meters that you descend from that point, the temperature rises 1 Celsius degree. This rapid rise in temperature continues for several kilometers. After that, the temperature increases more slowly, but steadily.

Pressure During your journey to the center of Earth, your instruments also record an increase in pressure in the surrounding rock. The deeper you go, the greater the pressure. Pressure is the force pushing on a surface or area. Because of the weight of the rock above, pressure inside Earth increases as you go deeper. Pressure During your journey to the center of Earth, your instruments also record an increase in pressure in the surrounding rock. The deeper you go, the greater the pressure. Pressure is the force pushing on a surface or area. Because of the weight of the rock above, pressure inside Earth increases as you go deeper. Pressure

A Journey to the Center of the Earth Three main layers make up Earth's interior: the crust, the mantle, and the core. Each layer has its own conditions and materials.

The Crust The crust is a layer of rock that forms Earth's outer skin. On the crust you find rocks and mountains. But the crust also includes the soil and water that cover large parts of Earth's surface.

The Crust The crust is the dry land and the ocean floor. It is very thin like an onion. Thinnest under the ocean and thickest under the mountains km thick

The Crust Oceanic crust is made up of mostly of basalt (A). Basalt is dark, dense, and fine texture. Continental crust is mainly made up of granite (B). Granite forms continents, less dense, large crystals, light colored, and coarse grained.

The Mantle The next layer is the mantle, a solid made of hot rock. The uppermost part of the mantle is the lithosphere. “Litho” means stone and is about 100 km thick.

The Mantle The largest part of the mantle is the asthenosphere. It is hotter and under increasing pressure. It is a soft and bendable like plastic. Asthenes means weak. But this layer is far from weak. It can flow slowly. The mantle is approx. 3,000 km thick.

The Core The Earth’s core consists of two parts - a liquid outer core and a solid inner core. Iron and nickel (metals) make up both parts of the core.

The Core The outer core is a layer of molten metal that surrounds the inner core and behaves like a thick liquid. The inner core is a dense ball of solid metal. In the inner core, extreme pressure squeezes the atoms of iron and nickel so much that they cannot spread out and become liquid.inner core

The Core The outer and inner cores make up about one third of Earth's mass, but only 15 percent of its volume. The inner and outer cores together are just slightly smaller than the moon. Temperatures range between which is as hot as the sun’s surface.

Earth’s Magnetic Field Currents in the liquid outer core force the solid inner core to spin at a slightly faster rate than the rest of the planet. These currents in the outer core also create Earth's magnetic field, which causes the planet to act like a giant bar magnet.

Earth’s Magnetic Field

Tectonic Plates Tectonic plates are pieces of the lithosphere that move around of top of the asthenosphere. The lithosphere is like a jigsaw puzzle. Tectonic plates are pieces of the lithosphere that move around of top of the asthenosphere. The lithosphere is like a jigsaw puzzle.

A Giant Jigsaw Puzzle

Comparing plates Cocos plate vs. South American plate

A Tectonic Plate Close-Up Figure 5

Like Ice Cubes in a Bowl of Punch Ice cubes floating in a bowl. Tectonic plates “float” on the asthenosphere in a similar way. Ice cubes floating in a bowl. Tectonic plates “float” on the asthenosphere in a similar way.

Mapping the Earth’s Interior Seismic waves Seismographs Seismic waves Seismographs