Earth's Interior

oceanic crust

Averages 5- 10 km thick. It is composed of basaltic or mafic rocks. Mafic rocks are silicate rocks that are rich in iron and magnesium and are thus more dense than the felsic/granitic rocks that make up the continental crust. Most oceanic crust is below sea level (no surprise there

Lehman Discontinuity

Predicted by Inge Lehmann in 1936 Boundary between outer and inner core defined by an increase in seismic wave velocity from outer to inner core and by seismic wave reflection off the solid inner core

disconinuity

A surface at which seismic wave velocities change. Mark the boundaries between layers.

inner core

The core is SOLID and composed mainly of iron. Although the inner core is very hot, pressure from the weight of the rest of the Earth doesn't allowed the material to melt. Iron's normal temperature of melting is 15350C, but in the earth inner core it could stand 40000C with no melting.

Asthenosphere

a zone in the upper mantle of the earth, consisting of hot, plastic rock. extending from a depth of about 75km to about 200 km (124 mi). lies beneath the lithosphere.

outer core

Because less weight is exerted on the outer core, the pressure is less there, so iron and nickel present here in liquid state. The molten outer core flows at the very slow rate which means electrons from the metals produce an electrical current. This electrical current powers the earth's magnetic field which protects the earth from "solar winds" (charged particles from the sun.

continental crust

Between 20 and 70 km thick. Composed of granitic or felsic rocks (silicates SiO2), which are lighter in color and less dense than basaltic rocks of the oceanic crust. Most of continental crust is above sea level.

Gutenberg Discontinuity

Between the mantle and outer core 2,900 km below the surface primary seismic waves (P waves) decrease in velocity while secondary seismic waves (S waves) disappear completely.

core

Differs from the rocky mantle and crust in composition. Composed mainly of metals such as iron (Fe) and probably small amount of nickel (Ni).

Compositional Layers

Layers based on chemical composition ~ what they are made of crust, mantle, core

Mechanical Layers

Lithosphere Asthenosphere Mesosphere Inner core Outer core

Mesosphere

Lower mantle. Strong, dense mantle material. Does not flow like the asthenosphere.

Lithosphere

Made up of Earth's crust and the upper part of the mantle. extends to a depth of about 80 km. Makes the tectonic/lithospheric plates of the earth.

Key Concepts

Our knowledge about the structure Earth's interior comes from studying how different types of seismic waves, created by earthquakes, travel through Earth. Earth is composed of multiple layers, which can be defined either by composition or by mechanical properties. The crust, mantle, and core are defined by differences in composition. The lithosphere, asthenosphere, mesosphere, and outer and inner cores are defined by differences in mechanical properties.

Crust

Rigid, outermost layer of our planet. Ranges from 5km to 70km thick less than 1% of the Earth's volume. 2 main types of crust = continental and oceanic

Mantle

The mantle is composed of hot iron and magnesium-rich silicate rocks. More so than any crust material. Flow in the mantle occurs as convection currents; hot material in the mantle rises, cools and then sinks. Motion is very very slow! Mantle is elastic which means it behave in plastic manner.

Mohorovičić Discontinuity or Moho

the boundary between the Earths crust and the mantle. The change in the speed of earthquake waves (seismic waves ~ primary and secondary waves) led to the discovery of the boundary.