Earth's Interior

differences in density and physical state inside the earth can be identified by

measuring and examining seismic waves

the layers of the earth based on chemical composition

crust, mantle, core

Earthquake waves move quickly thru

dense rocks. an increase in velocity = an increase of density.

Earth’s Crust

The outermost layer of the Earth. It is the thinnest layer, ranging from about 5 to 70km in thickness.

Two types of crust

Continental & Oceanic. Both types are made mainly of oxygen, silicon, and aluminum.

Continental Crust

• The thickest layer of the Earth's crust that is found under the continents.

• It is about 20-70KM thick

Oceanic Crust

The thinner layer of the earth that’s found under the ocean basins. It is about 7-10KM thick.

Continental Crust Composition

• composed mainly of granitic rock

• less dense and thicker than oceanic crust

• older than oceanic crust, some rocks estimated to be over 3.8 billion yrs old

Oceanic Crust Composition

• Composed mainly of basaltic rock

• Denser and thinner than continental crust

• Younger than continental crust because it is constantly being remade at the mid-ocean ridge

• The age does not exceed 200,000 years.

Earth’s Mantle

• The layer of hot, solid material beneath the Earth's crust.

• It is the thickest layer with a depth of approximately 2,900KM making up 67% of Earth's total mass.

• can be divided into an upper and lower layer.

Upper Mantle

relatively rigid and contains the asthenosphere, a semi-fluid layer that allows the movement of tectonic plates

Lower Mantle

contributes to the overall convection and heat transfers within the Earth's interior.

Earth’s Core

The innermost layer of the Earth that extends from below the mantle to the center of the Earth

Core Composition

• mostly metallic iron, with nickel and contains much less oxygen, silicon, aluminum and magnesium than the mantle.

• It is the densest layer and it makes about one-third of the Earth's mass (33%)

• The outer boundary has a depth of 2890 to 5150km thick. 

• It is made up of molten material and causes the Earth's Magnetic Field

Outer Core

A liquid layer composed mainly of molten iron with small amounts of sulfur & nickel. It has a thickness of about 2,300 kilometers

Inner Core

A solid central part of the Earth. It has a radius of about 1,220km and is composed of solid iron, nickel, and sulfur.

Inner Core

the hottest part of the Earth, with temperatures ranging from 4,000 to 6,000 degrees C

Layers of the Earth based on Physical Properties

Lithosphere, Asthenosphere, Mesosphere, Outer Core, Inner Core

Lithosphere

• The outermost rigid layer of the Earth that consists of the crust and the rigid upper part of the mantle

• 0 to 100 km (40-60 mi) thick

• Lies above the asthenosphere

• Divided into tectonic plates.

Asthenosphere

• The weak layer of the mantle in which the lithospheric plates float and move 

• Hot and Partially molten

• Extends from approximately 100 to 350km (60 to 220 mi) below the Earth's surface

The weak sphere

also called the asthenosphere

The rock sphere

also called the lithosphere

Mesosphere

• The strong lower part of the mantle

• Rock moves slower than the asthenosphere.

• despite high temperature, the extreme pressure keeps the rocks strong.

The middle sphere

also called the mesosphere

Moho

The boundary that separates the mantle and crust

Inge Lehmann

predicted the existence of the innermost layer in 1936

explained that there is another region within the core through seismic reflection

shadow zones

where seismic waves cannot be detected. located 103 to 143 degrees away from the epicenter.

Primary Waves or P Waves

• fastest kind of body waves

• can move through solid rocks & liquid layers

• aka pressure waves

movement:

• push & pull

S Waves or Shear Waves

• can only travel through solid rocks

• movement is side to side

Andrija Mohorovičić

found an abrupt speed change when reached a depth of 30-60km below the surface. He concluded that boundaries were passing from one rock layer into the denser rock layer. passing from the crust to the mantle.