Chapter 9 Section 1 VOLCANIC ERUPTIONS

 A vent or fissure in the Earth’s surface through which magma and gases are expelled VOLCANO

Nonexplosive  Most common  Produce relatively calm flows of lave  Can be huge amounts Explosive  Much rarer  Effects can be incredibly destructive  Ash from explosions can circle in upper atmosphere for years causing climate changes ERUPTIONS

 Vents- and opening at the surface of the Earth through which volcanic material passes  Magma chamber- the body of molten rock that feeds a volcano  Lava- liquid magma flows from a volcano’s vents FEATURES OF A VOLCANO

 “Aa”- pours out quickly forms brittle crust with jagged pieces  “ Pahoehoe”- flows slowly “ way from a candle” glassy surface, rounded wrinkles  “Pillow” – underwater, rounded lumps shaped like pillows  “Blocky” – Cool and stiff does not travel far from vent, oozes, forms jumbled heaps of sharp-edged chunks 4 TYPES OF LAVA

 If water content is high explosive eruptions are likely  If rich with silica explosive eruptions are likely  Magma that contains less silica has a more fluid, runnier consistency- gases can escape more easily explosions less likely to occur HOW MAGMA EFFECTS ERUPTIONS

Pyroclastic Material  Volcanic blocks- largest pieces of pyroclastic material, solid rock  Volcanic bombs- are large blobs of magma that harden in the air  Lapilli- “little stones” pebblelike bits if magma that harden before they hit the ground  Volcanic ash- forms when the gases in stiff magma expand rapidly and the walls of the gas bubbles explode into tiny, glasslike slivers- makes up most of pyroclastic material