Geo Quiz 11/6/15

reference geoid

imaginary equipotential surface

core superrotation

inner core rotates slightly faster than the rest of the Earth-- it makes an extra rotation about 20-25 years

geophysics

science treating of the forces that modify the earth

core-mantle boundary

the presence of a shadow zone means that deep in the Earth a major interface exists where seismic waves abruptly refract down (implying that the velocity of seismic waves suddenly decreases). This interface lies at a depth of about 2900 km. The density contrast across this boundary is greater than the density contrast between the crust and water.

s-waves

the second-fastest type of seismic wave; cannot travel through materials that are completely liquid; also known as shear waves and secondary waves

upper mantle

the soft layer of the mantle on which the lithosphere floats; also known as the asthenosphere -above 660 km

Archimedes principal

states the buoyant force on any object is equal to the weight of the volume that the object displaces.

travel time

the time it takes for a wave to travel from the focus to a seismograph station along a given ray is the ___ along that ray.

s-wave shadow zone

the zone ≥103° from the epicenter of an earthquake; suggests the outer core is a liquid, careful observations of P-wave refraction patterns indicate inner core is a solid. This means that S-waves cannot pass through the core at all.

velocity-versus-depth curve

used to detect nuclear explosions; funded the installation of an array of seismometer stations scattered around the world

seismic tomography

uses seismic waves collected from all over the world to create a computer-generated, three-dimensional image of Earth's interior

gravitational potential energy

when gravity acts on an object but still can't make the object move

mantle upwelling

where cooler and denser mantle is sinking

north magnetic pole

where earth's magnetic field points directly up and down

mantle downwelling

where warmer and less dense mantle is rising

magnetic anomaly

One in a pattern of long, narrow bands of high or low magnetic intensity on the seafloor that are parallel to and almost perfectly symmetrical with respect to the crest of a mid-ocean ridge

low-velocity zone

between about 100 and 200 km deep in the mantle beneath oceanic lithosphere, seismic velocities are slower than in the overlying lithospheric mantle. Within this zone, the prevailing temperature and pressure conditions cause peridotite to melt partially, by up to 2%, the melt coats solid grains and fills voids between grains.

inner core

A dense sphere of solid iron and nickel at the center of Earth -made of solid iron alloy

outer core

A layer of molten iron and nickel that surrounds the inner core of Earth -made of liquid iron alloy

permanent magnet

A magnet made of material that keeps its magnetism

equipotential surface

A surface on which all points are at the same potential (standing water in a pond)

refraction

Bending of light

field force

Force that can exist between objects, even in the absence of physical contact between the objects.

gravity anomaly

Reading of gravity different from expected

south magnetic pole

The Earth's magnetic pole under the ice north of Canada is a/an _____ ________ _____.

geoid

The actual shape of Earth, which is rough and oblate, or slightly squashed. Earth's diameter is longer around the equator than along the north-south meridians

electromagnet

The arrangement of waves of radiant energy in order of wavelength and frequency.

isostasy

The balance between changes within the Earth's crust and mantle, where material is displaced in response to an increase (isostatic depression) or decrease (isostatic rebound) in mass at any point on the Earth's surface above. Such changes are frequently caused by advances or retreats of glaciers.

reflection

The bouncing back of a wave when it hits a surface through which it cannot pass.

wave front

The crest, trough, or any continuous portion of a two-dimensional or three-dimensional wave in which the vibrations are all the same way at the same time.

lower mantle

The lowest portion of mantle, a zone of rigid rock -below 660 km

p-wave shadow zone

The region on Earth's surface, 103° to 142° away from an earthquake epicenter, in which P waves from the earthquake are absent.

seismic-reflection profile

To view rock structure beneath sea floor, strong low-frequency sounds are produced by explosions (depth charges) or air guns. These sound waves penetrate beneath the seafloor and reflect off the contacts between rock layers and fault zones just like sonar reflects off the bottom of the sea.

isostatic equilibrium

What specifically describes the balance between the lithosphere floating atop the asthenosphere?

p-waves

a primary wave, or compression wave; a seismic wave that causes particles of rock to move in a back-and-forth direction parallel to the direction in which the wave is traveling; P waves are the fastest seismic waves and can travel through solids, liquids, and gases

dynamo

generator for producing electricity A machine that generates electricity

gravimeter

measures differences in gravity because the density of an ore deposit usually differs from that of the surrounding rock

seismic-velocity discontinuities

occur at depths where pressure causes atoms in minerals to rearrange and pack together more tightly, thereby changing the rock's physical character. Corresponds to a phase change.

transition zone

the area in between the upper and lower mantle -region between 410-660 km

Moho

the boundary between the earth's mantle and crust

seismic ray

the changing position of an imaginary point on a wave front as the front moves through rock. Perpendicular to wave fronts, so that each point on the wave front allows a slightly different ray.