Geoscience Unit 1 Layered Earth and Its Magnetic Field

Compositional Layers

Compositional Layers

Determined by their components (crust, mantle, core).

Continental Crust

Portion of the earth's crust that primarily contains granite, is less dense than oceanic crust, and is 20-50 km thick.

Oceanic Crust

Portion of Earth's crust, usually below the oceans, thinner and higher in density that continental crust, and basaltic rather than granitic in composition. 0-7km thick.

Upper Mantle

depth of 400 km, temperature of approx. 500 - 1,200 Kelvin

Lower Mantle

The deepest section of the mantle, stretching from 670 km down to the core-mantle boundary.

Core

Center of the earth

Mechanical Layers

Determined by their physical properties and strength/rigidity. contains the lithosphere, asthenosphere, mesosphere, and the outer core.

Lithosphere

Includes the crust and uppermost mantle. Its average thickness is 100km but ranges from about 75km beneath ocean basins to about 125km under the continents. Temperatures range from 300-500 degrees Celsius.

Asthenosphere

The upper layer of the earth's mantle, plastic and partly molten, in which convection is thought to occur, about 350km thick. Average temperature of 1,800 degrees Celsius.

Mesosphere

The strong, lower part of the mantle between the asthenosphere and the outer core (~35 km thick)

Outer Core

the liquid layer of the Earth's core that lies beneath the mantle and surrounds the inner core; responsible for the Earth's magnetic field.

Inner Core

A dense sphere of solid iron and nickel at the center of Earth. Up to 7,000 degrees Celsius.

Magnetic Field

The area of magnetic force around a magnet.

Tectonic Plates

Sections of the Earth's crust that move due to convection currents in the Earth's mantle.

Seismic Waves

Vibrations that travel through Earth carrying the energy released during an earthquake

P waves

A type of seismic wave that compresses and expands the ground. The fastest; (6-8 km/s) they are the first to arrive.

S waves

A type of seismic wave that moves the ground up and down or side to side. Also known as shear waves, slower than P Waves.

Surface Waves

Most destructive, travel in the Earth’s surface, and are the slowest to arrive.

Shadow Zone

Zone where NO seismic waves are detected

Convection Currents

Circular currents in the mantle caused by the magma being heated by the core of the Earth.

Solar Wind

A stream of electrically charged particles produced by the sun's corona

Magnetic Reversal

a switch in the direction of Earth's magnetic field so that the magnetic north pole becomes the magnetic south pole and the magnetic south pole becomes the magnetic north pole.

Paleomagnetism

the study of changes in Earth's magnetic field, as shown by patterns of magnetism in rocks that have formed over time.

Dipole

A molecule that has two poles.