| bentonite |
either of two clays that are formed by the decomposition of volcanic ash, and that are very absorptive and capable of expanding to several times their normal volume. |
| caldera |
a large volcanic crater, esp. one whose diameter greatly exceeds that of the vent within it. |
| cinder |
(pl.) any of various residues of burning, such as ashes, slag, or volcanic lava. [1/4 definitions] |
| earthquake |
a shaking or other movement of part of the earth's surface, resulting from volcanic activity or the sudden release of tension along geologic fault lines. |
| lava |
molten rock erupting from a volcano or volcanic fissure. [1/2 definitions] |
| natural disaster |
a disaster, such as an earthquake, flood, or volcanic eruption, that is caused by natural rather than human forces and which destroys life and property. |
| Nevado del Ruiz |
a Colombian volcano that erupted in 1985 after having been dormant for 150 years, causing 23,000 deaths in what was the world's second most deadly volcanic eruption of the twentieth century. |
| nonvolcanic |
combined form of volcanic. |
| nuée ardente |
a thick volcanic cloud that explodes and pours down the sides of a volcano. |
| obsidian |
a dark, shiny volcanic glass, often used in jewelry, that fractures in a smooth, shell-like curve. |
| perlite |
a volcanic glass with distinctive concentric cracks, used in the manufacture of concrete and plaster, and thermal and acoustic insulation. |
| phenocryst |
a large and usu. conspicuous crystal embedded in volcanic rock containing many such crystals. |
| phonolite |
a fine-grained volcanic rock that rings when it is struck. |
| pitchstone |
a glassy rock of volcanic origin having the appearance of lustrous pitch. |
| plate |
a tectonic plate, any of the several segments of Earth's crust and upper mantle that move in relation to one another causing such phenomena as continental drift and volcanic eruptions. [1/10 definitions] |
| plate tectonics |
(used with a sing. verb) the geologic theory that the earth's crust consists of several independent plates floating on semiliquid magma, whose constant motion is the cause of continental drift, volcanic eruption, and the like. |
| pyroclastic |
relating to or consisting of fragments of rock that were formed by volcanic or igneous activity. |
| rhyolite |
a fine-grained, volcanic rock that is similar to granite in composition and has a high silica content. |
| seismometer |
an instrument that measures movement of the ground, such as movement caused by an earthquake, volcanic eruption, or explosion. |
| solfatara |
a volcanic fissure that gives off sulfurous vapors and steam. |
| tectonic plate |
any of the several segments of Earth's crust and upper mantle that move in relation to one another causing such phenomena as continental drift and volcanic eruptions. |