What does Earth's interior consist of?

Answer 1

Earth's Layers

All depths are from the surface of the Earth.

The Crust--The outer skin of the planet is composed of igneous, metamorphic, and sedimentary rock.

Continental Crust: Comprised predominately of rocks most resembling granite, the continental crust is relatively thick compared to the oceanic crust with a depth that ranges from 30 km to 50 km. The average specific gravity of continental crustal rock is 2.7.

Oceanic Crust:

At an average depth of 5 km to 10 km, the oceanic crust is thinner than the continental crust. Oceanic crustal rocks are composed mainly of the igneous rocks basalt, diabase, and gabbro, which are mafic in composition. The average specific gravity of oceanic crustal rock is 2.9.

Lithosphere: See below.

The Mantle--The layer directly below the crust which is delineated from the crust by the Mohorovicic Discontinuity, where seismic waves increase in velocity. The division between the mantle and the crust is a chemical one, the rocks and constituent minerals being higher in magnesium and lower in silicon and aluminum than crustal rocks. The mantle comprises 84% of Earth's volume.

Upper Mantle: Lithosphere: The uppermost mantle consists of hard rock and is attached to the crust and comprises the lithosphere. The lithosphere is comprised of tectonic plates which 'float' independently of each other. The lithosphere contains more mantle than crust. Oceanic lithosphere ranges from 50 km to 100 km in thickness, and continental lithosphere ranges from 40 km to 200 km. Asthenosphere: Just below the lithosphere lies the asthenosphere, an area of highly viscous but solid rock. Its viscosity allow it to move slowly over time, which it does as it transfers heat to the lithosphere via convection currents. These convection currents are responsible for the movement of Earth's tectonic plates. The depth of the asthenosphere averages somewhere between 100 km and 200km with depths up to 410 km.

Transition Zone:

The depth of the transition zone is between 410 km and 660 km. The rock here is mostly peridotite, a coarse grained igneous rock, kept from melting by extremely high lithostatic temperatures. Temperatures in the transition zone range from 1400 degrees C to 1600 degrees C.

The Lower Mantle:

The depth of the lower mantle ranges from 670 km to 2798 km. Little is known about the lower mantle other than that seismic waves indicate it is fairly homogenous in lithology.

D'':

The D'' area of the mantle extends from 2798 km to 2900 km, which is the boundary between the mantle and the liquid outer core. At this level, the pressures are enormous, roughly equal to 1.4 million units of atmospheric pressure, and temperatures are over 4,000 degrees C.

The Outer Core:

The outer core lies at a depth from 2900 km to 5150 km. It's composed of liquid iron and nickel along with small amounts of lighter elements, with temperatures ranging from 4,000 degrees C to 6,100 degrees C near the boundary with the inner core.

The Inner Core:

From the boundary with the outer core to the center of the Earth, a distance of about 1220 km is the solid sphere of the inner core, a ball of incredibly hot iron-nickel alloy. Temperatures here reach between 5,000 and 7,000 degrees C, and pressures are calculated to be around 3,000,000 units of atmospheric pressure. Despite the high temperature, at these pressures the metals cannot remain molten.