3.1 – Earth’s Interior  Essential Questions: 1. How Do Geologists Learn About Earth’s Interior? 2. What Are the Features of Earth’s Crust, Mantle, and Core?

How Do Geologists Learn About Earth’s Interior?  Geologists use direct evidence from rock samples and indirect evidence from seismic waves to learn about Earth’s interior.

Evidence From Rock Samples  Rocks from drilled holes as deep as 12.1 km.  Rocks from volcanic eruptions as deep as 100 km.  Earth’s radius is 6,371 km.  Scientists try to recreate Earth’s interior conditions in the lab. Kola Superdeep Borehole on the Kola Peninsula in Russia. Only 12,262 meters deep. Less than 1/5 th of 1% of Earth’s mean radius.

Evidence From Seismic Waves  Seismic waves are produced by earthquakes.  The speed and direction changes in the waves give clues about the interior structure and materials of the Earth.

What Are the Features of Earth’s Crust, Mantle, and Core?  The three main layers of the Earths are the crust, the mantle, and the core.  These layers vary greatly in size, composition, temperature, and pressure.

Interior Pressure and Temperature  The deeper inside of Earth, the greater the pressure.  Pressure is the result of a force pressing on an area.  Temperature also increases with depth. As the molecules bounce off of the sides of the box they exert pressure.

The dark line in this diagram illustrates how temperature increases with depth inside of the earth (this is called the geothermal gradient). The lighter line shows the position of the solidus (point at which liquid material solidifies). The shaded area represents solid regions. Note that temperatures in the outer core are higher than the solidus, so the outer core in liquid!

The Crust  Earth’s crust is the outer layer of rock that forms Earth’s outer skin.  A solid layer of rock that includes both dry land and the ocean floor.  Mostly oxygen and silicon.

Types of Crust

The Crust  Between 5 and 40 km thick.  Thickest under mountains.  Thinnest under oceans. This diagram also shows the isostasy that exists. The thicker crust extends deeper into the mantel.

The Crust  Oceanic crust is made of basalt, a dark, fine-grained rock.  Continental crust is made mostly of granite, a rock that is light in color with coarse grains.

The Mantle  The mantle is made of rock that is very hot, but solid.  3,000 km thick.  Divided into layers based on physical characteristics. Lithosphere Aesthenosphere Mesosphere

The Mantle - Lithosphere  Uppermost layer of the mantle that includes the crust.  Strong, Hard, and Rigid.  ≈ 100 km thick.

The Mantle - Aesthenosphere  “Soft”, plastic layer of the mantle under intense temperature and pressure.  The plasticity allows for movement (aka: plate tectonics).

The Mantle - Mesosphere  Stiffer than the aesthenosphere due to increasing pressure.  Extends all the way to Earth’s core.

The Core  Made of mostly nickel and iron.  Consists of two parts:  Dense, liquid outer core. (2,258 km thick)  Dense, solid inner core. (1,222 km thick) I’m the size of the moon!!!

The Core – Outer and Inner  The outer core is a layer of molten metal surrounding the inner core, which stays solid due to pressure.  Both are mostly iron and nickel, but traces of oxygen, sulfur, and silicon are thought to exist there.

The Core – Earth’s Magnetic Field  The movement of Earth’s molten outer core creates a magnetic field with two poles like a bar magnet.  This allows compasses to point to magnetic north.