2 What is A Volcano?A VOLCANO is an opening in Earth’s surface that often forms a mountain when layers of lava & ash eruptAfter many thousands or even millions of years, magma reaches earth’s surface and flows out through an opening called a VENT.The steep walled depression around a volcano’s vent is the CRATER.
3 Magma vs. Lava Magma – molten material inside a volcano Lava – molten material on earth’s surface
5 Where do volcanoes occur? Where plates move APARTAKA: Divergent plate boundariesWhere plates move TOGETHERAKA: Convergent plate boundaries
6 Where do volcanoes occur? 3. HOT SPOTSareas of earth that melt rock & force magma upward
7 Pacific Ring of Fire area around the pacific plate where earthquakes & volcanoes are common
8 Active vs. DormantMost of Earth’s volcanoes are DORMANT, which means they are not currently activeThere are more than600 active volcanoesin the worldThe most active volcanoin the world is Kilauea in Hawaii
10 Eruptions Eruptions can either be quiet or explosive. Two factors to determine the type of eruption:Amount of water vapor and other gases trapped in the magma.Whether the magma is basaltic or granitic.
11 Trapped GasesGases like water vapor and carbon dioxide are trapped in magma by the pressure of the surrounding magma.As magma nears the surface, pressure is reduced.Gas escapes easily = quiet eruptionGas trapped under high pressure = explosive eruption
12 Magma CompositionBasaltic Magma – contains less silica, very fluid, and produces quiet, nonexplosive eruptions.Example: Kilauea, HawaiiGranitic Magma – contains a lot of silica, very thick, and high water content. Gets trapped in vents causing pressure to build up resulting in explosive violent eruptions.Example: Mount Saint Helens
13 VIDEOSKilauea EruptionMount Saint Helen Eruption