Earth’s Interior C4S1
How have geologists learned about Earth’s inner structure? • Geologists have used two main types of evidence to learn about Earth’s interior: direct evidence from rock samples and indirect evidence from seismic waves
Evidence from Rock Samples • Rocks from inside Earth give geologists clues about earths structure. • This is direct evidence. Something you can physically observe. • Geologists have only drilled 3.8 kilometers into the Earth’s crust. • To reach the Earth’s center they would have to dig 6,000 kilometers which is 1600 times the deepest mine.
Evidence from Seismic Waves • Geologist observe seismic waves and study how they travel through the Earth. • Different types of seismic waves travel differently. The speed of the waves and the paths they take reveal the structure of the planet. • Using data from seismic waves, geologists have learned that earth’s interior is made up of layers. Like an Onion.
Seismic Waves • Vibrations that travel through Earth carrying the energy released during an earthquake.
What are the characteristics of Earth’s crust, mantle and core? • The three main layers of Earth are the crust, the mantle, and the core. These layers vary greatly in size, composition, temperature and pressure.
Temperature • Digging from the surface the rock starts off cool. • ~ about 20 meters down starts to get warmer. For every 40 meters you descend the temperature increases 1 Celsius degree. • This rise in temperature continues for several tens of km. • After that it continues more slowly, but steadily
Pressure • Results from a force pressing on an area. • The deeper you go the greater the pressure
Crust • The layer of rock that form’s Earth’ s outer surface. On the crust you will find rocks, mountains, soil and water The crust is about 40 km thick
What are the characteristics of Earth’s crust? • The crust is a layer of solid rock that includes both dry land and the ocean floor.
Crust This outer layer of rock is thinner than the layers beneath (mantel and cores). The crust is thickest under mountains, and is thinnest under the ocean. In most places the crust is between 5 and 40 km thick, but under mountains is is up to 70 km thick.
Crust (continued) Oceanic crust is the crust beneath the ocean. It consists of rocks such as Basalt (buh SAWLT) Basaltis a dark igneous rock with a fine texture
Crust (continued) Continental crust is the crust that from continents. It consists mainly of rocks such as granite. Granite is an igneous rock that usually is a light color and has a coarse texture.
What are the characteristics of Earth’s mantle? • Earth’s mantle is made up of rock that is very hot, but solid. Different layers if the mantle have different physical characteristics.
Mantle • The layer of hot, solid material between Earth’s crust and core. • Overall the mantle is nearly 3000km thick
Lithosphere The uppermost part of the mantle and the crust together form a rigid layer called the lithosphere. In Greek, lithos, means “stone” The lithosphere averages about 100 km thick.
ASthenosphere The softer layer of the mantle on which the lithosphere floats. Below the lithosphere is the Asthenosphere. It is hotter and under more pressure. This part of the mantle is softer. Beneath the Asthenosphere the mantle is solid material which extends all the way to the Earth’s core
What are the characteristics of Earth’s core? • The core is made mostly of the metals iron and nickel. It consists of two parts – a liquid out core and a solid inner core. • Together, inner and outer core are 3,486 km thick
Outer Core A layer of molten iron and nickle that surrounds the inner core of Earth.
Inner Core A dense sphere of solid iron and nickel at the center of Earth. (a dense ball of solid metal) Extreme pressure squeezes the atoms of iron and nickel so much they cannot spread out and become liquid.
The Core and Earth’s Magnetic Field. When you use a compass, the coompass needle aligns with the lines of force in Earth’s magnetic field. Scientist think movement in the liquid outer core create Earth’s magnetic field.