Do Now: What is your favorite layered food? Lesson 4b September 26, 2017 Aim: What are the Characteristics of the Earth’s Interior Layers? Do Now: What is your favorite layered food?
The Layers of the Earth The Earth’s interior is divided into five distinct layers: The Lithosphere (aka, the Crust) The Asthenosphere The mantle (aka, stiff mantle) The outer core The inner core They were created as the results of having different densities. These layers and their properties can be seen on page 10 of your reference table.
The Lithosphere The lithosphere is the thinnest of the layers. It ranges from 3 - 44 miles thick. It is the layer that we live on. It is made up of solid rock, and contains all the land above and below the oceans. The crust is not perfect, it is cracked into several pieces called plates. These plates are constantly moving. There are two types of crust: Continental and oceanic crust. Continental crust is thicker and less dense than oceanic crust.
The Moho Boundary The Moho is the boundary between the crust and the asthenosphere in the Earth. This is a depth where seismic waves (waves created by earthquakes) change velocity (the S-wave suddenly stops) and there is also a change in chemical composition. *** The moho is not a layer but an imaginary boundary the separates the solid rocky crust from the liquidy molten asthenosphere.
The Asthenosphere The asthenosphere is located just under the crust. It is about 700 miles thick. It is made up of semi molten rock called magma. Lava that comes through the crust from volcanoes, come from the asthenosphere. The asthenosphere is very important because the forces that move the crustal plates and causes earthquakes originates from convection currents in the asthenosphere.
Convection Currents Convection currents are the movement of materials based from change is density. In the asthenosphere, the part of the asthenosphere closest to the center of the Earth is much hotter than the layer of the asthenosphere nearest the crust. This difference in temperature affects the density of the magma in the asthenosphere. These differences in density create circular currents in the magma that push and pull the crust along the surface of the Earth.
Magma cools down; Density increase; Magma sinks Magma hits the crust and moves along the bottom Magma heats up; Density decrease; Magma rises Magma sinks; Magma heats up
The Mantle The mantle is the thickest layer. It is over 1800 miles thick. It is made of very hot, molten rock. (liquidy) Every rock that is in or on the crust originated from the mantle. ***Sometimes the asthenosphere is included as part of the mantle. The upper mantle is the asthenosphere.
The Cores At the center of the Earth, there are two layers composed of the most dense material: The outer and inner cores. The outer core is a layer of liquefied nickel and iron. It is about 1350 miles thick. The inner core is made of solid nickel and iron. It is about 1250 miles thick. The inner core is responsible for the magnetic field that surrounds the Earth. The magnetic field protects the Earth from solar winds and radiation that is given of from the Sun. Without this field, the Earth’s atmosphere would be ripped of the surface of the Earth.