Exploring Earth's Interior

Low velocity zone between - and - km

Low velocity zone between 100 and 200 km

Melting curve

Melting curve indicates the temperature at which materials melt as depth increases in the Earth

Melting occurs where the - lies to the - of the -

Melting ocurs where the geotherm lies to the right of the melting curve

Only - are known not to - waves.

Only fluids are known not to transmit shear waves.

P and S waves travel more rapidly through - than through -

P and S waves travel more rapidly through basalt than through granite

P waves typically travel at speeds between - and - km/s. The slower values correspond to a P wave traveling in -, the highest represents the speed near -.

P waves typically travel at speeds between 1 and 14 km/s. The slower values correspond to a P wave traveling in water, while the higher represents the speed near the base of the mantle.

Waves of different types have a common feature:

The velocity at which they travel depends on the material that they pass through

The velocity of - waves changes with -

The velocity of P waves changes with depth

The - shows the depths at which seismic velocity suddenly - and is useful for establishing the - and - in the Earth

The velocity vs. depth profile shows the depths at which seismic velocity suddenly changes and is useful for establishing the principal layers and sublayers in the Earth

Velocity of seismic waves - with depth

Velocity of seismic waves increases with depth

Waves are fastest in - and - material

Waves are fastest in solid, cold material

Waves are slowest in - and - material

Waves are slowest in liquid, hot material

Waves - as they go through - to -, so their paths are -

Waves bend as they go through layer to layer, so their paths are curved

P wave shadow zone between - and - degrees

103 and 143 S

S wave shadow zone degrees and coverage

103 and beyond, about a third of the globe

An earthquake generates all - types (- waves (- and -) and - waves (- and -)

An earthquake generates all seismic wave types (Body waves (P and S) and Surface waves (L and R))

Boundaries in Earth's interior

Crust and mantle (Moho), mantle and outer core, outer core and inner core

Discovery of the - led geologists to surmise that the Earth has a - made of a - from the -

Discovery of the P-wave shadow zone led geolists to surmise that the Earth has a core made of a different material than the mantle

Earth is layered due to (3) that cause the seismic waves to - (-) when -

Earth is layered due to rock composition, elasticity, and temperature that cause the seismic waves to refract (bend) when transmitted between different rock layers

Geotherm

Geotherm curve indicates the change in temperature as depth increases in the Earth

Geothermal gradient

Geothermal gradient is the slope of the geotherm and indicates the rate of change of temperature with depth (degrees Celcius per kilometer)

If the Earth was not layered (meaning - and -, or -), seismic waves would -

If the Earth was not layered (no changes in pressure or composition with depth, or isotropic) seismic waves would travel a straight path

Reflection means the wave - the boundary, while refraction means the wave - the boundary

Reflection means the wave bounces off the boundary, while refraction means the wave goes through it

S wave velocity

S wave velocity is the square root of [the shear modulus (modulus of rigidity) over the density]

S waves typically travel at speeds between - and - km/s. The lower value corresponds to speed in - and the higher value corresponds to -

S waves travel at speeds between 1 and 8 km/s. The lower value corresponds to loose, unconsolidated sediment while the high value corresponds to the base of Earth's mantle.

Seismic waves through the interior are -; they do not follow a -

Seismic waves through the interior are curved; waves do not follow a straight path

Seismic waves travel faster in - than in - (temperature)

Seismic waves travel faster in a cold material than in a hot material

Seismic waves travel faster in - than in - (state of matter)

Seismic waves travel faster in a solid than in a liquid

When a wave is reflected or refracted, some of the energy is -

Some of the energy of one type is converted to waves of the other type

Sudden jumps in - define the - between - and - km

Sudden jumps in velocity define the - between 410 and 660 km

The temperature at the center of the Earth

Temperature at the center of the Earth is 5000 degrees Celsius

The Earth is layered and made of many - that conduct - at different -

The Earth is layered and made of many materials that conduct P and S waves at different velocities

The fact that the outer core is - was verified by -. When - strike the -, they fail to - (-).

The fact that the outer core is liquid was verified by the behavior of S waves. When S waves strike the core, they fail to emerge from the other side (S-wave shadow zone).

The outer core is - while the inner core is -

The outer core is liquid; the inner core is solid

There are no - in the - core

There are no S waves in the outer core

Seismic tomography has revealed (2)

Tomography reveals features in the mantle clearly associated with mantle convection and hot and cold rocks inside Earth

Body waves (- and -) have a characteristic that affects shaking: when they move through -, they are -

When body waves (P and S) move through layers of rock, they are reflected or refracted

When seismic waves move through layers of rock, they are - and/or -

When seismic waves move through layers of rock, they are reflected or refracted

P wave velocity equation

a is P wave velocity, K is bulk modulus (modulus of incompressibility of a material), u is shear modulus (modulus of rigidity)