Inside Edition The Earth’s Interior: A Hot Topic
A Planet at Rest? From the surface or from space the earth appears stable and calm Except for infrequent violent volcanic and earthquake activity the earth hides its volatile nature The key to understanding this side of the earth is understanding its interior
A Model of the Earth Inner Core Outer Core Mantle Crust
Differentiation Remember how the Earth Formed? The Nebula Hypothesis Planetesimals joined together to form protoplanets which were molten, at first Dense materials like iron and nickel would tend to sink towards the middle As cooling progressed lighter materials floated to the surface like “scum” and formed the crust This was all completed about 4 billion years ago
Inner Core 1216km (754 miles) in radius Rich in Iron and Nickel Intense Pressure and Heat: 3700 0 c (6700 0 f) Dense materials sank to core as earth cooled Solid
Outer Core 2270km (1410miles) thick Molten Iron and Nickel 1500ºc Less pressure than inner core liquid Inner and outer core = 1/6 volume, but 1/3 mass
Mantle 2900km (1800miles) thick Mainly Fe, Mg, Si, and O About 1200ºc Makes up 2/3 of Earth’s mass Less pressure than cores, but still pretty intense Plasticlike-partially molten compostion that can slowly “flow”
Crust 30-40km(19-25miles) average thickness Beneath mountains can reach 43 miles This thin layer that floats on denser mantle Average composition is basaltic Solid – Made of Plates if you were to imagine the Earth as a soccer ball, the crust would be about ½millimeter thick.
The Thickness of the Crust Varies: This is a contour map of the thickness of the Earth's crust. The contour interval is 10 km; it also include sthe 45 km contour for greater detail on the continents. Where are the thickest parts of the crust?
Rock Solid Continental Crust Thickest type of crust; - can be 43 miles thick beneath mtns. Very old rocks, 3.8 billion years old Lighter granitic composition
Do You Want Some Water With That Crust? Oceanic Crust Thinnest part of the crust, 4-7 miles thick Rocks are relatively young, only 200 million years old Dense basaltic composition
Crust and Mantle Lithosphere – cool, rigid upper layer of earth Asthenosphere – softer layer of the earth under the lithosphere Mesosphere – very slowly flowing layer under the asthenosphere The interaction of the crust and mantle gives rise to tectonic activity and crustal movement The crust and mantle are broken down into three different zones
Lithosphere Composed of the Crust and upper mantle Solid – rigid plates made of the lithosphere Varies from a few to 190 miles thick (62 miles average) Continental Crust Ocean Water Upper Mantle Lithosphere Oceanic Crust
Asthenosphere Very hot, weak zone of the upper mantle capable of flowing Temperatures reach 2600 0 F – hot enough to melt some of the mantle material This creates a soft layer about 200 miles thick that the overriding lithosphere “floats” upon The lithosphere can move independently of the asthenosphere