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grade 6 earthquakes
test on chapter 2 Emily science
| Term | Definition |
|---|---|
| Earthquake | The shaking and trembling that results from the movement of rock beneath Earth's surface. |
| Stress | A force that acts on rock to change it's shape or volume. |
| Shearing, tension and compression | The different kinds of stress that occur in the crust. |
| Shape and volume of rock | Changed over millions of years by shearing tension and compression. |
| Shearing | A stress force that pushes a mass of rock in two opposite directions. |
| Tension | A stress force that pulls on rock causing it to become thinner in the middle. |
| Compression | A stress force that squeezes rock until it folds or buckles |
| Deformation | Any change in the volume or shape of earths crust caused by the slow shift of Earths plates. |
| Fault | A break in Earth's crust where slabs of crust slip past each other. |
| Plate boundaries | Where faults occur because the forces of plate motion compress, pull, or shear the crust so much that the crust breaks. |
| Strike-slip faults | Faults created by the shearing forces of rocks slipping past each other sideways forming a transform boundary between the two plates. |
| The San Andreas Fault | An example of a strike-slip boundary that is a transform boundary. |
| Normal faults | Faults created by tension forces in the earths crust. Angled faults created by plates diverging or pulling apart. |
| Hanging wall | The block of rock that lies above an angled fault. |
| Footwall | The block of rock that lies below an angled fault. |
| The Rio Grande Rift Valley in New Mexico | An example of a normal fault where two pieces of Earth's crust are diverging. |
| Reverse fault | Faults created by compression, the hanging wall slides up and over the footwall. |
| Mt. Gould in Glacier National Park | An example of a reverse fault where the hanging wall slid up to form the mountain. |
| Friction | The force that opposes the motion of one surface as it moves across another surface |
| Mountains formed by faulting | Mountains formed when normal faults uplift a block of rock. When two normal faults form parallel to each other a block of rock is left lying between them. The hanging walls slip downward and the block is lifted.m |
| Mountains formed by folding | The collision of two plates causes compression which can lead to folding of the crust. |
| Folds | Bends in rock that form when compression shortens and thickens part of the Earth's crust. |
| Syncline | A fold in rock that bends downward in the middle to form a bowl. |
| Anticline | A fold in rock that bends upward into an arch. |
| Plateau | A large area of flat land elevated high above sea level |
| Focus | The point beneath Earth's surface where rock that is under stress breaks, triggering an earthquake. |
| Epicenter | The point on the surface directly above where rock that is under stress breaks. |
| Seismic waves | Vibrations that travel through Earth carrying the energy released during an earthquake. |
| The energy of the seismic waves that reach the surface | Is greatest at the epicenter. |
| P waves | The first waves to arrive. Earthquake waves that compress and expand the ground. The particles of the crust vibrate forward and back along the path of the wave. Travel through both liquids and solids. |
| S waves | Earthquake waves that vibrates from side to side as well as up and down. They cannot move through liquids. They shake structures violently. |
| Surface waves | Move slowly but produce the most severe ground movements. Shake side to side or up and down. |
| Seismograph | An instrument that records the ground movements caused by seismic waves as they move through earth. |
| The Mercalli Scale | A scale that rates earthquakes according to their intensity, the strength of the ground motion in a given place. The same earthquake can have different ratings because it affects different places differently. |
| The Richter Scale | A scale that rates earthquakes by the size of the seismic waves it produces, as measured by a mechanical seismograph. Good for small nearby earthquakes only. |
| The Moment Magnitude scale | A scale that estimates the total energy released by an earthquake. This scale can be used to rate earthquakes of all sizes, near or far. |
| An earthquake with a moment magnitude above 5.0 | An earthquake that causes great destruction. |
| Liquefaction | When an earthquake's violent shaking suddenly turns loose soft soil into liquid mud. |
| Aftershocks | An earthquake that occurs after a larger earthquake in the same area. |
| Tsunami | Large waves that are created when the ocean floor rises and displaces the water. |
| Base-isolated building | A building designed to reduce the amount of energy that reaches the building during an earthquake. |
| Creep meters | A wire stretched across a fault to measure the horizontal movement of the ground. |
| Laser-ranging devices | Uses a laser beam to detect fault movements. Calculates any change in time for the laser beam to travel to a reflector and bounce back. |
| Tiltmeter | Measures the tilting of the ground along the fault using water. |
| Satellite monitor | Detects small changes in elevation of the ground along a fault by bouncing waves down to the ground from space. |
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