| A | B |
|---|
| original horizonality | the idea that many kinds of rocks form in flat, horizontal layers |
| sea floor spreading | the idea that new crust is forming at ridges in the sea floor, spreading apart the crust on either side of the ridges |
| subduction | the sliding of a denser ocean plate under another plate when they collide |
| magnitude | the amount of energy released by an earthquake |
| seismic wave | a vibration that spreads out away from a focus when an earthquake happens |
| seismograph | a sensitive device that detects the shaking of the crust during an earthquake |
| aftershock | the shaking of the crust after the intial skaking of an earthquake |
| vent | a central opening in a volcanic area through which magma may escape |
| crust | Earth's solid, rocky surface containing the continents & ocean floor |
| plate tectonics | the idea that Earth's surface is broken into plates that move |
| magma | hot, molten rock below earth's surface |
| mantle | Earth's layer beneath the crust |
| subduction | where plates collide, the sliding of a denser ocean plate under another plate when they collide |
| divergent boundaries | where plates pull apart |
| convergent boundaries | where plates are colliding |
| fault-block mountain | mountain made by huge tilted blocks of rocks separated from surrounding rocks by faults |
| focus | the point where an earthquake starts |
| Mercalli scale | measures the effect such as the amount of damage done in a given location |
| Richter scale | measures the amount of energy |
| earthquakes happen more | at the edges of plates, where plates meet |
| earthquakes happen less | at the center of plates far from edges |
| a strike-slip fault | San Andrea Fault in CA |
| a reverse fault | Himalayas in India |
| a normal fault | Sierra Nevada in CA |
| epiccenter | the point on Earth's surface directly above the focus |
| seismongraph | a sensitive devise that detects the shaking of the crust |
| hot spot | a very hot part of the mantle, where magma can melt through a plate moving above it |
| lava | magma that reaches Earth's surface and flows out of a vent |
| crater | a cuplike hollow that forms at the top of a volcano around the vent |
| cinder-cone volcano | a steep-sided cone that forms from explosive erruptions of hot rocks, ranging from particles to boulders |
| composite volcano | a cone formed from explosive eruptions of hot rocks followed by a flow of lava, over and over |
| shield volcano | a wide, gently sloped cone that forms from flows of lava |
| geothermal energy | heat from below Earth's surface |
| a fold mountains | Appalachian Mts |
| fault-block mountains | Grand Tetons of Wyoming |
| weathering | the breaking down of rocks into smaller pieces by natural proceses |
| erosion | the picking up and removal of rock particles |
| soil horizon | any of the layers of soil from the surface to the bedrock below |
| humus | material in soil fromed by the breakdown of plant and animal material |
| chemical weathering | breaks down rocks by changing their compostion; oxidation & the action of of acids are important in this process |
| mechanical weathering | breaking down of rocks by physical changes; frost action, moving water, action of plants & animals |
| soil | the end result of weathering |
| till | a jumble of many sizes of sediment deposited by a glaciers |
| deposition | the dropping off of sediment |
| moraine | a deposit of many sizes of sediments in front of or along the sides of a glacier |
| mass wasting | the downhill movement of Earth material caused by gravity |
| dike | an undergound sturcture that forms when magma hardens in vertical cracks |
| sill | an undergound sturcture that forms when magma hardens between horizontal layers of rock |
