Science, Chapter 7
Terms
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- Alfred Wegener
- theory of continental drift-continents moving very slowly across Earth's surface
- seismogram
- record of seismic waves
- vent
- central opening through which gas and magma burst through
- surface waves
- travel along Earth's surface
- seismic waves
- waves of energy sent through Earth's crust when parts of the crust move suddenly
- San Andreas fault
- extends the full length of California
- energy of seismic waves
- What causes the shaking of an earthquake?
- focus
- point underground where the faulting in an earthquake occurs
- L waves
- surface wave that travel slowest, but causes most damage, make ground swell and roll like ocean waves.
- diverging boundaries
- two plates move away from each other; molten rock rises to fill the gap, creating new crust (rift valley)
- intensity
- surface effects of an earthquake measured by what can be seen and felt on surface
- fault at sliding boundary
- roucks grind against each other as they move horizontally past each other in oppositie directions.
- crust
- the thin, rocky outer layer of Earth that makes up the continents and the ocean floor
- faulting
- movement of rocks along a fault...the rocks crack or split into blocks
- faulting
- can produce dramatic cliffs when a large section of rock is forced upward or downward (Rocky Mountains)
- fold mountains
- mountains that form where two plates collide and force layers of rock into folds
- Richter scale
- scale that measures earthquake's magnitude (3.5 minor, 7.5 major)
- magnitude
- size of an earthquake
- fault-block mountains
- mountains that form along fault lines where blocks of rock fall, are thrust up, or slide; form at converging or diverging boundaries
- folding
- often occurs at the edge of a continent and results in long, narrow mountain ranges (Andes)
- core
- Earth's innermost structure
- earthquake
- violent shaking of Earth's crust as built-up energy is released
- epicenter
- Where is the intensity of an earthquake the strongest? Why? Closest point to focus, where seismic waves are strongest.
- composite
- cone shapes, steeper than shield, not as steep as cinder
- magma, rock fragments, gases
- three types of volcanic material ejected
- fault at diverging boundary
- force stretches rock: rocks are stretched until they snap, causing one block to move down along a sloping crack
- epicenter
- point on Earth's surface directly above the focus of an earthquake
- plate boundaries
- earthquakes and volcanos change Earth's surface usually at
- crater
- bowl-shped mouth formed after a volcano eruption
- volcano
- opening in Earth's surface through which melted rock, hot gases, rock fragments, and ash erupt
- body waves
- travel through Earth's interior
- seismograph
- sensors that detect and measure vibrations of Earth's crust
- sliding boundaries
- two plates slide past each other, moving in opposite directions
- plate boundaries
- where are mountains usually formed
- converging boundaries
- two plates move toward each other
- P waves
- Body wave that is fast, can pass through solids and liquids, can return to Earth's surface where they cause back-and-forth motions of rock
- fault
- crack in Earth's crust along which movement takes place
- plate tectonics
- theory that giant plates of crust are moving slowly across Earth's surface
- subduction
- upper plate forces the edge of the lower plate under the surface (ocean trench)
- mantle
- thick layer of Earth's structure just below Earth's crust
- magma
- melted rock below Earth's surface
- shield volcanos
- broad, low, dome-shaped volcano (lot of lava flows smoothly)
- lithosphere
- shell formed from Earth's solid upper mantle and crust
- fault at converging boundary
- force squeezes rock: rocks are compressed as they come together, causing one block to move up along a sloping crack as the other moves down
- Ring of Fire
- zone that borders the Pacific Ocean--home to many earthquakes and volcanoes
- lava
- magma when it reaches Earth's surface
- dome mountain
- mountains that form when magma pushes up on Earth's crust but does not break through
- sea-floor spreading
- happens in the middle of the ocean floor at diverging boundaries
- cinder cone
- cone shaped with steep sides (mostly rock fragments erupt)
- aftershocks
- miniquakes caused by continued seismic wave activity after initial earthquake
- S waves
- body wave that is a little slower, cause surface to move up and down, can only travel through solids (cannot return to surface).
- Two types of seismic waves
- body and surface