2. The Layers of the Earth © Copyright 2006. M. J. Krech. All rights reserved.

3. The Atmosphere The Earth is surrounded by a blanket of gases called the atmosphere Provides air we breathe and shields us from the Sun’s harmful rays

4. A Closer Look Main Zones of the Earth: –Crust –Mantle (Upper and Lower) –Core (Inner and Outer)

6. Have We Journeyed to the Center of the Earth? Clip

7. Layers of the Earth How far have scientists drilled into the Earth? 7.6 miles –Only 0.2% of the distance to the earth’s core

8. Layers of the Earth

9. Crust Outermost Layer One we live on Rocky Most studied and understood layer Thinnest & lightest layer 8 - 50 km wide Temperature ranges from air temp on top to 870C (1600F) Density 2.7-3.3 g/cm 3 Constantly cracking

10. There are two major types of crust Oceanic crust: is composed entirely of basalt and is relatively thin (~ 5 km), and dense (~3.0 g/cm 3 ).Oceanic crust –Most of the present day oceanic crust is less than 200 million years old because it is continuously being created at oceanic ridges and destroyed by being pulled back into the mantle in subduction zones by the processes of plate tectonics.oceanic ridges mantlesubduction zonesplate tectonics

11. Crust Continental crust: on the other hand, is made primarily of less dense rock like granite (~2.7 g/cm 3 ). It is much thicker than oceanic crust, ranging from 15-70 km.Continental crust video

14. Mantle 2800km wide total Composed of very hot, dense rock. Upper part is rigid, lower part is plastic – flows like asphalt Convection Currents cause it to flow. Causes crust to move Mg, Fe, Al, Si, O From 3700C to 1000C (about 1600F to 4000F) Density 3.3 – 5.7 g/cm 3

16. The upper mantle and crust together form what is called the Lithosphere or the rigid part of the earth. The lower mantle which flows slowly, at a rate of a few centimeters per year, is called the Asthenosphere. Video

17. Core…Two Parts Outer Core –Liquid Iron, Ni, S –2300km wide –From 3700C to 4300C (~4000F) –Density 9.9– 12.2 g/cm

18. Inner Core –Temperature and pressure are so great, metal become solid. –Solid Iron –Over 1400km thick –Temperatures can get as high as 5000C (~9000F) –Pressure may reach 45,000,000 lbs per square inch –Density: 12.6– 13.0g/cm 3 VideoVideo

19. Thickness of the Earth’s Layers Crust: from Earth’s surface (0 km) to ~8 km under oceans and ~50 km under continents Upper Mantle: from the bottom of the crust to ~ 670 km Lower Mantle: from the bottom of the Upper Mantle (~670 km) to ~ 2885 km Outer Core: from the bottom of the Lower Mantle (~ 2885 km) to ~5200 km Inner Core: from bottom of Outer Core (~5200 km) to 6400 km (the center of the earth)