Earth's Interior Layers

Mantle

Largest of earth's layers (82% of earth's volume) is divided into 3 parts. Solid rock layer between the crust and the core. Convection occurs in the mantle.

Outer Core

Liquid layer of iron-nickel-sulfur Flow of metallic iron within this zone generates Earth's magnetic field.

Mesosphere

Lower Mantle hot, semi-solid rock that has the consistency of hot asphalt

Lithosphere

Earth's outermost layer consists of the crust and uppermost mantle and forms relatively cool, rigid shell (Brittle part of upper mantle)

Data from Seismographs

The velocity of both S- and P-waves is determined by the density and rigidity of the material. Waves travel faster in denser more rigid material.

Layers of Earth

When Earth first formed, gravity pulled the densest materials to the center of the Earth, and 3 main layers resulted.

Reflection

When seismic (energy) waves travel through the earth and some energy bounces off harder layers (boundary between 2 layers of different density)

Attenuation

When some seismic energy is absorbed as it encounters materials

Refraction

When some seismic energy travels through earth but gets bent, changing the direction the wave is traveling (caused by density differences). Waves are refracted (bent) when they pass from a layer with higher density to a layer with lower density.

Basalt

a dark, fine-grained volcanic rock that makes up the more dense oceanic crust (floats lower)

Granite

a very hard, granular, crystalline, igneous rock that makes up the less dense continental crust (floats higher)

Factor that affects seismic waves: Temperature

colder = faster

Factor that affects seismic waves: Angle of incidence

controls how much is reflected and how much is absorbed

Factor that affects seismic waves: Vertical arrangement of layers

controls the resultant direction of travel

Factor that affects seismic waves: Distance

farther = more attenuation

Magma

hot fluid or semifluid material below or within the earth's crust from which lava and other igneous rock is formed by cooling

Convective flow

A convective flow is the motion of a fluid due to differences in density

P waves

A pressure wave where the material vibrates back and forth in the same direction as the wave movement. Can pass through rock. Can pass through a liquid

S waves

A sideways wave in which the disturbance vibrates material side to side, perpendicular to the direction to the wave movement. Can pass through rock. Can NOT pass through a liquid

Seismic Waves

A vibration that moves through the Earth

P Wave Shadow Zone

An earthquake will send out P-waves over the entire globe, except for an area between 103degrees and 142degrees of arc from the earthquake. no P-waves are received here. P-waves appear to be refracted by the core, which leaves a shadow.

Seismograph

An instrument located at or near the surface of the earth that records seismic waves

Asthenosphere

Beneath the lithosphere, a soft, comparatively weak, hot, slowly flowing layer of rock (Ductile part of upper mantle)

Core-Mantle Boundary

Both mantle and core undergo convection. Great changes in seismic velocity.

Moho

Boundary separates the crust from the underlying mantle. Separates rocks of significantly different density, composition, and viscosity.

Inner Core

Despite its higher temperature, the material in the inner core (iron-nickel alloy) is compressed into a solid state by the immense pressure

What influences (earthquake) wave paths

Distance Density Temperature Angles they strike boundaries (angles of incidence) Composition of earth's layers (liquid vs. solid) Vertical arrangement of layers

Shadow Zones

Seismic Waves do not reach certain areas on the opposite side of Earth from a large Earthquake

Body Waves

Seismic Waves that travel through the Earth's interior, spreading outward from a disturbance in all directions

Surface Waves

Seismic waves that travel on the Earth's surface

S Wave Shadow Zone

larger than the P-wave shadow zone. S-waves are not recorded in the entire region more than 103 degrees away from the epicenter. S-waves DO NOT pass through the core at all

Factor that affects seismic waves: Liquid vs. Solid

solid = faster; p-waves and s-waves liquid = slower; no s-waves

Density

the degree of compactness of a substance. D=M/V With seismic waves the higher density is the faster the wave moves

Crust

the thinnest rocky outer layer of Earth (contains MOHO boundary). Made up of continental crust and oceanic crust.