5 ERUPTIONSAs magma rises the pressure surrounding it decreases. (It is not as deep anymore) This allows gases in and around the magma to expand. These expanding gases push the magma out of the volcano.Eruptions can spew outAsh – fine dust specksCinders – pebble-sized particlesBombs – baseball to car sizedpieces!
7 2 types of eruptionsQUIET: magma low in silica; magma flows easily, gases bubble out slowly and gently.EXPLOSIVE: magma high in silica; thick/sticky; doesn’t always flow out of the crater; can plug it like a cork; gases get trapped and build up pressure until they “explode”.PYROCLASTIC FLOW: when the volcano hurls out a mixture of hot gases, ash, cinders, and bombs.
13 Volcano Hazards Fire Ash can bury towns Landslides Mudslides Flooding (melted snow)
14 Stages of Volcanic Activity Volcanoes are classifiedas:ACTIVE – a live volcano that is erupting or will in the near futureDORMANT – “sleeping” may erupt againEXTINCT – a dead volcano; unlikely to ever erupt again.
15 TYPES OF VOLCANOESWide, gently sloping, usually form at a hot spot, lava pours out gentlyLava has high viscosity, steep, cone shaped hill, more explosive eruptionsCombination of both; sometimes gently flowing lava, sometimes explosive, alternating layers of ash/cinders & lava
27 Geothermal Activity Geo – means “earth” Therme – means “heat” Geothermal is heat produced by the Earth (actually magma!)Hot springs & Geysers are types of geothermal activity found in volcanic areas.