| A | B |
|---|
| magma | partially melted lithosphere rock, dissolved gases and water |
| decompression melting | melting in the lower lithosphere due to a drop in pressure that ocurs as molten rock in the asthenosphere rises |
| divergent plate volcanism | occurs as mantle rises to fill the gap as 2 plates move away from each other |
| convergent plate volcanism | forms island arcs as 1 plate subducts under another |
| Ring of Fire | long belt of volcanoes encircling the Pacific Ocean |
| hot spot | believed to be form within a plate due to hot mantle plumes over which a plate moves, creating a chain of volcanoes in which only the most recent is active |
| viscosity | a substance's resistance to flow |
| silica | continental rock |
| basalt | oceanic rock |
| pahoehoe lava | hot, fast-flowing lava that forms smooth, braided surfaces |
| ah ah | cooler, slower-moving lava that forms rough surfaced, jagged & sharp surfaces |
| pyroclastic material | any solid particle produced in a volcanic eruption and ejected into the air by that eruption |
| ash | pyroclastic material less than 2mm in size |
| cinders | pyroclastic material 2-64 mm in size |
| lapilli | another name for cinders |
| blocks | hardened pyroclastic material greater than 64 mm in size |
| bombs | glowing pyroclastic material greater than 64 mm in size |
| magma chamber | pocket of magma beneath the surface |
| pipe | cylinder-shaped pathway from magma chamber to the opening of the volcano |
| vent | fissure or crack in the surface through which magma escapes |
| crater | steep-walled depression at the summit of a volcano |
| shield volcano | broad, dome-shaped structure formed by basaltic lavas |
| cinder cone volcano | short-lived, small, steep-sided structures formed by gas-rich lavas that eject pyroclastic materials as opposed to lava |
| composite cone volcano | large, nearly symmetrical volcanic mountains composed of layers of lava and pyroclastic materials |
| stratovolcano | another name for a composite cone |
| caldera | a depression in a volcanic mountain formed by the collapse of the volcano's top |
| volcanic neck | Exposed pipe of an ancient volcano after the cone is eroded away |
| lava plateau | forms when lava leaks out through fissures, spreading out across a wide area instead of forming a cone |
| lahar | a mudflow caused by water-soaked volcanic ash |
