| A | B |
|---|
| volcano | a mountain that forms when molten rock, called magma, is forced to the Earth's surface |
| lava | magma that flows onto the Earth's surface |
| pyroclastic material | fragments of rock that are created by explosive volcanic eruptions |
| shield volcano | a large, gently sloped volcano that forms from repeated, nonexplosive eruptions |
| cinder cone volcano | a small, steeply sloped volcano that forms from moderately explosive eruptions of pyroclastic material |
| composite volcano | a volcano made of alternating layers of lava and pyroclastic material |
| crater | funnel-shaped pit around the central vent of a volcano |
| caldera | a circular depression that forms when a magma chamber empties and causes the ground above to sink |
| rift | a deep crack that forms between tectonic plates as they separate |
| hot spot | a place on Earth's surface that is directly above a column of rising magma called a mantle plume |
| Pahoehoe | lava that flows slowly, like wax dripping from a candle |
| Aa | a type of lava that has a jagged surface |
| subduction | the movement of one tectonic plate under another |
| mantle plumes | rising columns of magma |
| vent | magma rising through holes in the Earth's crust |
| fissure | long cracks in the Earth's crust |
| silica | a basic building block of most minerals |
| lava plateau | a wide, flat landform that results from repeated nonexplosive eruptions of lava that spread over a large area |
| rift zone | an area of deep cracks that form between two tectonic plates that are pulling away from each other |
| mid-ocean ridge | chains of volcanoes or mountains in the ocean |
| ash | dust-sized particles that are expelled from a volcano |
| pumice | frothy lava with gas that solidifies when it reaches the surface and can float on water |
| pyroclastic flow | produced when enormous amounts of hot ash, dust, and gases are ejected from volcanoes. |
