Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Igneous rocks The Beginning What is a rock? Rocks are solid materials made of one or more minerals. Common Igneous rockforming minerals Olivine Pyroxene Amphibole Feldspar Mica Quartz Formations from molten materials Material from a volcano or deep inside the earth cools to form extrusive and intrusive rocks What is Magma? Magma is molten rock located beneath the surface of the Earth often collects in a magma chamber. Magma is a complex hightemperature (between 650 and 1200 °C) silicate solution that is ancestral to all igneous rocks Magma Continued Magma has a lower density than the surrounding rocks of the mantle. Similar to a lava lamp Less dense because of its composition. Magma that reaches the earths surface is called lava Extrusive Fine grained with small crystals Magma that doesn’t reach earths surface Intrusive Coarse texture with large crystals Igneous rocks Granite Cools slowly Pumice, Obsidian, Scoria -cool quickly - pumice and scoria gas is steamed out Basaltic rocks Basaltic (or mafic) magma has a high iron and magnesium content. Associated with Shield volcanoes and and hot spots Dark in color. Intermediate rock Andesitic magma has a mixture of iron, magnesium, sodium, and silica (SiO4). Intermediate between Basaltic and Granitic magma. Granitic or Felsic Rock Granitic rock (rhyolitic magma) has a high concentration of Silicon and Aluminum. Associated with composite volcanoes light in color Comparing Rocks U.S.G.S - J. Johnson http://volcanoes.usgs.gov/Products/Pglossary/VolRo cks.html#flow Component of Igneous Rocks from U.S.G.S Shield Volcanoes Mauna Loa (top 2 pics) is the world’s largest Basaltic eruptions Lava flows Not very explosive http://www.geology .sdsu.edu/how_volca noes_work/index.ht ml Lava falls, channels, solid basalt, and lava tube Composite or Stratovolcanoes Composition varies Alternating basaltic to rhyolitic lavas and teprha (solids), overall compostion is andesitic Explosive Pinian eruptions Abundant in Ring of Fire along subduction zones Mt. Fuji, Japan shown right Explosive Eruptions and pyroclastic flows Cinder Cone or Scoria Cone Volcano Composed of basalt tephra, occasionally andesitic Most common, smallest volcanoes Associated with stombolian eruptions - Mt Etna, Paracutin Strombolian eruptions Blasts of highly vesiculated basalt = scoria with lots of holes Pyroclastics or Tephra Classified on the basis of size Ash - < 2mm Lapilli - pea to walnut sized Blocks and bombs How Volcanoes Work For more information on volcanoes: http://www.geology.sdsu.edu/how _volcanoes_work/index.html