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Unit 1 Chapter 6
MMS Science 8 Earthquakes
Term | Definition |
---|---|
Plate | A large section of Earth's crust and rigid upper mantle that moves around on the asthenosphere. |
Fault | The surface along which rocks move when they pass their elastic limit and break. |
Earthquake | The vibrations produced when rocks break along a fault. |
Normal fault | A break in rock caused by tension forces, where rock above the fault surface moves down relative to the rock below the fault surface. |
Reverse fault | A break in rock caused by compressive forces, where rock above the fault surface moves upward relative to the rock below the fault surface. |
Strike-slip fault | A break in rock caused by shear forces, where rocks move past each other without much vertical movement. |
Wave | A rhythmic movement that carries energy through matter and space. |
Seismic wave | A wave generated by an earthquake. |
Focus | In an earthquake, it's the point below Earth's surface where energy is released in the form of seismic waves. |
Primary wave | A seismic wave that moves rock particles back-and-forth in the same direction that the wave travels. |
Secondary wave | A seismic wave that moves rock particles at right angles to the direction of the wave. |
Surface wave | A seismic wave that moves rock particles up-and-down in a backward rolling motion and side-to-side in a swaying motion. |
Epicenter | The point on Earth's surface directly above an earthquake's focus. |
Seismograph | An instrument used to register earthquake waves and record the time that each arrived. |
Crest | The highest point of a wave. |
Magnitude | The measure of the energy released during an earthquake. |
Liquifaction | This occurs when wet soil acts more like a liquid during an earthquake. |
Tsunami | A seismic sea wave that begins over an earthquake focus and can be highly destructive when it crashes on shore. |
Folded mountain | Mountain formed when horizontal rock layers are squeezed from opposite sides, causing them to buckle. |
Upwarped mountain | Mountain formed when blocks of Earth's crust are pushed up by forces inside Earth. |
Fault-block mountain | Mountain formed from huge, tilted blocks of rock that are separated from surrounding rocks by faults. |
Volcanic mountain | Mountain formed when molten material reaches Earth's surface through a weak crustal area and piles up into a cone-shaped structure. |