vocab words 1-5
definition of aa
A basaltic lava flow that breaks up into sharp fragments as the lava advances.
definition of bomb
a large, molten pyroclastic mass ejected from volcanoes
definition of crater
a steep-walled depression at the summit of a volcano
definition of epicenter
a stream that flows for only part of the year
definition of lahar
A thick,dense mixture of water and pyroclastic material that flows down the slopes of a volcano
definition of ash
silt and sand-sized pyroclastic material that may be carried in the atmosphere hundreds or thousands of kilometers downwind from a volcano
definition of caldera
a large volcanic crater
definition of crust
the outermost layer of earth
definition of fault scarp
a small cliff on earth's surface caused by verticle movement along a vault
definition of lapilli
a walnut-sized pyroclastic particle
definition of basement rocks
the deeper grantic and gneissic parts of earth's continental crust
definition of cinder
a pea -sized pyroclastic particle
definition of dike
definition of fissure eruption
a volcano eruption were lava is erupted from long cracks in earth's crust called fisssures rather than from craters at the summits of volcanoes
definition of magma chamber
a pool of molten rock or partially molten rock in earth's crust, often beneath volcanoes
definition of batholith
the largest type of pluton, covering an erea of at least 100 km2
definition of cinder cone
a small volcano built mainly from loose pyroclastic material such as cinders and lapilli
definition of earthquake
a violent shaking of earths crust caused by a rapid release of energy
definition of focus
the point beneath earth's surface where an earthquake originates
definition of magnitute
a measure of the amount of energy released by an earth-quake
definition of block
a large, solid pyroclastic particle ejected from volcanoes
definition of composite cone
a volcano made of alternating layers of lava flows and pyroclastic material
definition of elastic rebound
the sudden release of stored energy in rocks which results in movement along a fault
definition of hotspot
a region of hotter than normal rocks in earth's mantle that may be the source of magma for some volcanoes in the interior of tectonic plates
definition of mantle
the thick layer in earth's interior between the crust and the core, composed of dense silicate rocks such as peridotite.