Intro - Introduction to Geology February 11, 2008 PICK UP...

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Introduction to Geology February 11, 2008 PICK UP ELVIS PACK I. Can’t see clearly through quartz crystal. II. For Wednesday: Extrusion Lava Λ Λ l l Intrusion Magma February 13, 2008 I. Igneous Processes a. Extrusion- lava b. Intrusion- magma II. Volcanoes a. The shields shapes, the slopes, and the explosiveness of the eruptions i. Lava like water, just pours out ii. Pyroclastic debris -ash, cinders, all the junk blown out b. Three forms of shields- i. Shield : low slope angles (mostly lava) 1. formed by Hawaiian eruptions, not very explosive a. ii. Composite cones : intermediate slope angles, “classic volcano”, are alter national of lava and Pyroclostic debris 1. Strombolian eruptions, alternate explosive and non- explosive 2. iii. Cinder : high slope angle, mostly pyroclastic debris, generally in a houser-shoe shape,not full circular 1. Plaean , all explosive
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2. c. Types of Eruptions- i. Strombolian - characterized by huge clots of molten lava bursting from the summit crater to form luminous arcs through the sky. Collecting on the flanks of the cone, lava clots combine to stream down the slopes in fiery rivulets. The explosions are driven by bursts of gas slugs that rise faster than surrounding magma. 1. ii. Peléan - a large amount of gas, dust, ash, and lava fragments are blown out of a central crater, fall back, and form avalanches that move down slope at speeds as great as 100 miles per hour. Such eruptive activity can cause great destruction and loss of life if it occurs in populated areas 1. iii. Hawiian - fissure-type eruptions, lava spurts from a fissure on the volcano's rift zone and feeds lava streams that flow down slope. In central-vent eruptions, a fountain of lava spurts to a height of several hundred feet or more. Such lava may collect in old pit craters to form lava lakes, or form cones, or feed radiating flows. 1. d. Two lava types:
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i. ‘A’a- stony with rough lava, moves very slow 1. ii. Pahoehoe- smooth, unbroken lava; moves very quickly, hotter than ‘A’a 1. e. Intrusions: f. Zenolith i. Always have a higher temperature and higher pressure. February 20, 2008 Weathering and Erosion- institu passive I. Weathering a. Mechanical- reducing the size, but not changing the composition, except by segregation (reduction in size but no comp change) b. Chemical- change composition, usually accompanied by change in size c. All BRS minerals chemically weather to clay as a size and comp except quartz i. Shale is made of clay size grains, is most common b/c 95% of what is available can become clay (dirt) ii. Sandstone is 2 nd most common iii. Limestone is 3 rd most common d. Things that promote weathering i. Cracks e. Hoodoo- “balanced rock” Concordant Discordant Tabular Sill Dike Massive Cacocilil Batholith
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i. f.
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This note was uploaded on 04/07/2008 for the course GEOL 1113 taught by Professor Manger during the Fall '07 term at Arkansas.

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Intro - Introduction to Geology February 11, 2008 PICK UP...

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