Geology -Study Guide for Exam 2.docx

Geology -Study Guide for Exam 2.docx - Catalina Ceja...

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Catalina Ceja Physical Geology Geol 1403/P02 Physical Geology Study Guide for Exam 2 1. Define Igneous Rock, Magma, and Lava. Igneous Rock = A type of rock formed a molten material that has cooled and solidified. (Melted) Magma = Molten rock material that originates deep within the earth. (inside earth) Lava = Molten rock material that reaches the earth’s surface due to a volcanic eruption. (out of the volcano) 2. How old is the Earth? What was the first type of rocks to form? Most Geologist think that the first rocks on Earth were formed as the outer crust slowly solidified about 4.6 billion years ago. Therefore, the first rocks formed were Igneous rocks. 3. 80% of the Earth’s crust is composed of igneous rocks. 4. Igneous rocks can be divided into two basic categories Extrusive and Intrusive 5. Describe extrusive igneous rocks and intrusive igneous rocks. Extrusive = Igneous rocks that cool (quickly) at the surface of the earth, generally due to some type of volcanic eruption. (Exit) Intrusive = Igneous rocks cooled (slowly) somewhere beneath the surface of the earth. (Inside, below) 6. How are Igneous Rocks Classified? According in to two criteria Texture and Mineral composition . 7. Define Texture.
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Texture = Generally refers to the size and shape of the mineral grains (crystals) in the igneous rock. Texture of igneous rock is primarily controlled by cooling rate 8. Describe Phaneritic, Aphanitic, Pegmatite, Glassy, and Porphyritic. Describe the Effects of Cooling on the Textures of Igneous Rocks Phaneritic = (Intrusive) Most crystals >1mm. Crystals can be see without magnification. Aphanitic = ( Extrusive) Most crystals >1mm.
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  • Fall '15
  • Igneous rocks, Sedimentary rocks

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