2/29 earthquakes vocab

Stress

A force acting on rock to change its shape or volume

Tension

Plates pulling apart, causing thinning in the middle

Compression

Squeezing of rocks, one plate pushing against another, leading to folding or breaking

Shearing

Pushing two rocks in opposite directions, causing them to slip past each other

Normal Fault

Caused by tension, pulling apart of rocks at divergent plates

Reverse Fault

Compression causes rocks to push together, resulting in blocks moving in the reverse direction of a normal fault

Strike and Slip Fault

Shearing forces causing rocks to slip past each other sideways with little up or down motion

Thrust Fault

Major compressional forces pushing the hanging wall completely on top of the footwall

Hanging Wall

Rock layer sitting over the footwall, slipping downward during movement along a fault

Footwall

Rock layer moving down, located below the fault zone

Rift Valley

Area where two normal faults occur

Fault-Block Mountains

Formed when two reverse faults cut through a block of rock, pushing it up

Plateau

Large elevated flat land above sea level

Mountains

Formed at convergent boundaries when continental plates collide and fold

Anticline

Upward bending fold in rock forming an arch

Syncline

Downward bending fold in rock forming a V-shape, occurring at thrust or reverse faults

Earthquake

Vibration of the earth due to the rapid release of energy, sudden movement of the earth's crust

Epicenter

Location on the earth's surface directly above the earthquake's focus

Focus

Point underground where the release of stress is located

Aftershock

Earthquake occurring after a larger earthquake in the same area

Liquefaction

Earthquake's shaking turning loose, soft soil into a liquid-like slurry

Seismic Waves

Carry energy away from an earthquake's focus

P Wave

Compresses and expands the ground

S Wave

Vibrates the ground from side to side

L Wave

Makes the ground roll like ocean waves

Deformation

Process affecting the shape, size, or volume of the Earth's crust

Richter Scale

Rates an earthquake's magnitude based on seismic wave size (1-10)

Modified Mercalli Scale

Rates earthquakes based on the level of damage at a given scale

Moment Magnitude Scale

Rates the total energy released by an earthquake using seismographs and other sources

Seismograph

Instrument recording and measuring earthquake seismic waves

Ring of Fire

Area with many earthquakes due to geologic activity

Tsunami

Large water bodies displaced by underwater earthquakes releasing energy into the water