A a o If the surface layer of the lava freezes and then breaks up due to the continued movement of lava underneath jumble of sharp angular fragments yielding a rubbly flow Bombs o Apple to refrigerator sized fragments of pyroclastic debris o Form when large lava blobs enter the air in a molten state and then solidify Caldera o A large circular depression with steep walls and a fairly flat floor formed after an eruption as the center of the volcano collapses into the drained magma chamber below Cinder cone o Consists of cone0shaped piles of tephra Tephra unconsolidated accumulations of pyroclastic grains slope of the cone approaches the angle of the repose of tephra meaning the steepest slope that the pile can attain without collapsing from the pull of gravity typically are symmetrical and have deep craters at their summits small pryoclastic eruptions Crater o A circular depression at the top of a volcanic mound Explosive pyroclastic eruption o Produce clouds and avalanches of pyroclastic debris Lahar o A thick slurry formed when volcanic ash and debris mix with water either in rivers or from rain or melting snow and ice on the flank of a volcano Lapilli o Pea to plum sized fragments o Consist of pumice or scoria fragments known as cinder o If formed from low viscosity lava it may become streamlined while flying through the air yielding teardrop shaped glassy beads known as Pele s tears Lava molten rock that has flowed out onto the Earth s surface Lava dome a dome like mass of rhyolitic lava that accumulates above the eruption vent Lava flows sheets or mounds of lava that flow onto the ground surface or sea floor in molten form and then solidify Magma chamber o An open space or a zone of highly fractured rock that can contain a large quantity of magma Pahoehoe o the surface texture of a basaltic lava flow when it finally freezes reflects the timing of freezing relative to its movements Flows with warm pasty surfaces wrinkle into smooth glassy rope like ridges Phreatomagmatic eruptions o An explosive eruption that occurs when water enters the magma chamber and turns into stream Pyroclastic debris o Fragmented material that sprayed out of a volcano and landed on the ground or sea floor in solid form o Finest volcanic ash consist of powder sized glass shards and pulverized rock generated during explosions Pyroclastic flow o Fast moving turbulent avalanches of hot ash and lapilli that rushed down the flank of the volcano o Can form when gravity overcomes the upward force and buoyancy of a rising ash column so that the column collapses and ash surges downward Shield Volcano o Resemble a soldier s shield lying on the ground o Broad gentle domes o Form either from low viscosity basaltic lava or from large pyroclastic sheets o Tend to be the largest o Only effusive eruptions Stratovolcano o Composite volcano o Large and cone shaped and consist of alternating layers of lava and tephra o Tend to be steeper near the summit o 2 nd largest o Alternate between effusive and large pyroclastic eruptions Volcanic ash Tiny glass shards formed when a fine spray of exploded lava freezes instantly upon contact with the atmosphere Volcano o An erupting vent through which molten rock reaches the Earth s surface or a mountain built from the products of eruption o Volcanic activity can build a towering snow crested mountain or can blast one apart o Can provide the fertile soil that enables agriculture to thrive or it can snuff out a civilization in a matter of minutes o Positions reflect the locations of plate boundaries rifts and hot spots Aftershock o Small earthquakes that follow a major earthquake o Happens because the movement of rock during the main earthquake produces new points of contact Earthquake o An episode of ground shaking o Most are a consequence of lithosphere plate movement they punctuate each step in the growth of mountains the drift of continents and the opening and closing of ocean basins o Ground shaking giant waves land slides and fires associated with earthquakes turn cities to rubble Epicenter o The point on the surface of the Earth that lies directly above the hypocenter Hypocenter the place in the Earth where rock ruptures and slips or the place where an explosion occurs focus Fault o A fracture on which sliding occurs o Are fractures on which slip or sliding occurs o Fault trace intersection between a fault and the ground surface o Fault scarp in places where an active normal or reverse fault intersects the ground one side of the fault moves vertically with respect to the other creating a small step o Stress causes faulting Liquefaction o Abrupt loss of strength of a wet sediment either sand or clay in response to ground shaking and can cause major damage during an earthquake o If it occurs in the sediment beneath a slope the ground above may give way and slide down the slope o May also cause bedding in unconsolidated sequences of sediment to break up and become contorted P waves o Primary waves o Compressional body waves o Travels fastest S waves o Secondary o Shear body waves R waves Rayleigh waves o Surface waves that cause the ground to ripple up and down o Slowest o Have the largest amplitude and arrive over a relatively long period of time Seismicity o Earthquake activity o Occur for several reasons Sudden formation of a new fault A sudden slip on an existing fault A sudden change in the arrangement of atoms ex A phase change in the minerals comprising rock Movement of magma in a volcano The explosion of a volcano A giant landslide A meteorite impact Underground nuclear bomb tests Seismic waves o Earthquake waves Seismogram o The waves traced by the pen on a seismograph provide a record of the earthquake o Horizontal axis represents time and the vertical axis represents the amplitude of the seismic waves Seismograph o An instrument that can systematically record the ground motion from an earthquake happening anywhere on earth Seismologist o Geoscientists who study earthquakes Anthracite o Bituminous transforms into this at higher temperature 200 300C o Shiny black hard coal Bituminous o Lignite becomes this at higher temperature 100 200 C becomes dull black Hydrocarbon o Chainlike or ringlike molecules made of carbon and hydrogen atoms o Type of organic chemical so named because similar chemicals make up living organisms o Some are gaseous and invisible some resemble watery liquids some appear syrupy and some are solid o Viscosity and volatility depend on the size of its