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The Earth’s Layers Notebook #4 January 22, 2016 8.E.5A.3 Following these notes you will be able to obtain and communicate information about the relative position, density, and composition of Earth's layers to describe the crust, mantle, and core. The Earth is ~ 4,000 miles (6,400 km) from surface to center. Earth has layers that have specific conditions and composition The 3 layers of Earth * Crust *Mantle *Core Crust Position *Outermost layer * Thinnest under the ocean * Thickest under continents * Crust & top of mantle called the lithosphere Mantle Position * Middle layer * Thickest layer * Top portion called the asthenosphere Core Position * Inner layer * Consists of two parts – outer core and inner core Density * Measures how heavy an object is for its size * Formula is mass volume * If an object's density is >1, it will sink * If an object's density is <1, it will float Crust Density * Least dense layer *Oceanic crust (basalt) is more dense than continental crust (granite) Mantle Density * Density increases with depth because of increasing pressure Core Density * Heaviest material * Most dense layer Crust Composition * Solid rock – mostly silicon and oxygen * Oceanic crust basalt * Continental crust granite Mantle Composition * Hot softened rock * Contains iron and magnesium Core Composition * Mostly iron and nickel * Outer core – slow flowing liquid * Inner core spinning solid * Scientists have been able to identify the composition of inner and outer core based on the movement of seismic waves through the Earth's layers * Scientists have been able to identify the composition of the mantle based on the movement of seismic waves through the earth's layers as well as materials ejected from volcanic activity. Most lava that erupts during volcanic activity is actually just melted crust and is not material from the mantle and/or the core. * The reason that the inner core is solid, despite being at very high temperatures, is because of the weight of all of the other materials above it (crust, mantle, and outer core). The pressure of these layers keeps the inner core solid * The movement of the inner and outer core results in Earth's magnetic field.