Geological Terms

aftershocks

smaller earthquakes following a large earthquake in the same area

compressed/ compression

crust is pushed together and folded by great forces in the earth's crust

continental shelf

land under water at the edge of a continent

depressed

an area of land is pushed downward from its original position

displacement

movement of the Earth's crust in relation to where it was originally, can be sideways or up and down

duration

the amount of time between first feeling the ground shake and the time it stops shaking during an earthquake

epicenter

the point on the Earth's surface directly above where the earthquake occured

fault

a crack in the ground along which one or both of the sides have moved either up, down, or sideways past each other

fiord (fjord)

U-shaped valley is carved to the sea during ice ages, and later flooded with water to form huge canals.

focus

place in the earth where the earthquake started

glacial deposits

soil, rocks and clays that were left behind by a glaciar

hinge line

a line of that does not move up or down which separates the areas of an earthquake that subsided from those that were uplifted

intensity (of earthquakes)

a way to measure earthquakes by the amount of ground shaking felt, damage done to buildings, and changes seen in the earth's surface

isoseismal intensity lines

lines drawn on a map telling where the edges of areas that had the same amount of shaking during an earthquake are

island arc

a chain of islands formed above the place where two of the Earth's plates meet

liquefaction (of soil)

when sand and soil act like a thick liquid during an earthquake

magnitude (of earthquakes)

a measure of the size of an earthquake on a scale of 1 to 10. Each number means the earthquake was ten times worse than an earthquake with the next lowest number.

normal fault

a fault in which one side of the rock has moved downward

paleosiesmology

study of earthquakes that happened before people started to record them

plate (tectonic)

a huge section of the Earth's surface which slowly moves. The edges of plates scraping together causes earthquakes

quick clay

a type of clay formed by glaciers that loses its shape when shaken

reverse fault

a fault in which one side of the rock moves up and over the other side

runup height

the height of the water level greater than normal when a tsunami runs up on land along a coast

rupture

the Earth's crust breaks

seiche

a sloshing of water back and forth in a small body of water, like in a bathtub

slump

a large area of land slides off a hillside

subducted

one plate is pulled under another at a plate boundary, causing earthquakes, melting, volcanoes, and mountains

subsidence

an area of land sinks

surge

a great rush of large volumes of water

tension

the earth's crust is stretched in opposite directions

topography

shape of land, under water or above it

tsunami

an open ocean wave generated by large scale motion of the sea floor

tsunami runup

the height above sea level to which the tsunami wave rises above land

uplift

an area is pushed upward from its original position

vertical displacement

land is pushed up or lowered from original position

zone of subsidence

the area of land that dropped lower than its original level

Learn more about the 1964 Good Friday Great Alaskan Earthquake

Other sites of interest:

United States Geological Survey Report on the Alaskan quake.

Credits