Geology.pdf - GEOLOGY Rocks Minerals Fossils Geologic Time and Plate Tectonics Geology Yosemite valley in California Geology Geology can and does tell

Geology.pdf - GEOLOGY Rocks Minerals Fossils Geologic Time...

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GEOLOGY: Rocks, Minerals, Fossils, Geologic Time, and Plate Tectonics
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Geology Yosemite valley in California
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Geology Geology can and does tell us about the history of the earth. All we have to do is understand the language. These fossils were found in Montana. These are ocean fossils called Ammonites. Montana? There’s no ocean in Montana!! There was . . . . . 350 million years ago!
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Rocks and the rock cycle There are three types of rock on the Earth. Igneous Sedimentary Metamorphic The igneous rocks of Mt. Shasta in California.
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Mt. Hood, Oregon
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Igneous rocks Igneous rocks form when hot melted rock (Magma or Lava), cools and hardens. Igneous rocks are identified according to the size of their mineral crystals. Large Crystals are “Intrusive” Small Crystals are “Extrusive” Large intrusive mineral crystals in Granite. Crystal size depends on the rate or speed of cooling of the liquid rock. See Figure 3.11 page 59
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Igneous rocks Igneous rocks form when hot melted rock (Magma or Lava), cools and hardens. Igneous rocks are also classified according to their color. Light colored igneous Felsic Dark colored igneous Mafic Light colored mineral crystals in Granite. Granite is Intrusive Felsic See Figure 3.9 page 58
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Have you ever seen black granite? No, actually, you haven’t
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Intrusive Vs. Extrusive Felsic Vs. Mafic
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Sedimentary Rocks Sedimentary rocks are formed from sediments which have been compacted and cemented together. This sediment may be fragments of other rocks (Detritus) or it may be chemical or organic. Sedimentary rocks are the most common type of rock on the Continents. Why? The fact that this sediment has been both compacted and cemented is very important . This is called “ Lithification .” Turned into stone
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Sedimentary rocks are usually classified according to the size of their sediment. Boulders: Just what it sounds like, up to a railroad freight car Cobbles: Golf ball to football size Pebbles: Pea to golf ball size Sand: Typical beach sand Silt: ½ the size of sand Clay: ½ the size of silt
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Sediments / Sedimentary Rocks: are indicators of the geographic environment in which they formed. Boulders: Deposited only by glaciers Cobbles: Deposited only by glaciers Pebbles / Conglomerate: Fast moving water Sand / Sandstone: A beach or swift river. Silt / Siltstone: Low energy environment, lake or very slow river. Clay / shale: Very still water such as a swamp. Limestone: Always means ocean
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The Glacial Front : During an ice age these were known to be thousands of feet high and moving forward about as fast as your fingernails are growing. Underneath these things, cobbles and boulders would be snapped off and carried along with the advancing glacier. Sometimes for hundreds of miles, and then dropped as the ice age ended and the glacier melts.
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Boulder sized Glacial Erratic in Iowa
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Glacial cobbles and boulders Cobbles and boulders in front of a glacier in Alaska, deposited very recently.
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