IgneousRX geo1301

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IgneousRX geo1301
2010-06-14 11:36:56
IgneousRX geo1301

IgneousRX geo1301
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    • A. There are three types of rocks-igneous, sedimentary, and metamorphic
    • B.The rock cycle shows the relationshi[s between the three types of rocks and how one type of rock may give rise to a different type of rock
  2. Igenous Rocks- Fire formed
    • 1. Magma-molten rock within the earth
    • a.Intrusive igneous rocks form from magmas
    • 2. Lava-molten rock that erupts on the earths surface
    • a. Extrusive igneous rocks form from lavas
    • 3.Both magma and lava may be composed of solids, liquids, gases.
    • 4. As magmas and lavas cool, minerals cystallize and grow until they the edges of other minerals, so igneous rocks are composed of interlocking minerals
    • 5.Ignous rocks are classified according to their texture and composition
  3. Igneous Rock Textures-Size, Shape, Araangement of Minerals
    • A. Coarse-grained (Phaneritic) texture
    • 1.All of the minerals are about the same size and are visisble to the naked eye
    • 2.Phaneritic texture develops because magma cools slowly
    • a.The surrounding rocks don't conduct heat well, so magmas may stay hot
    • for long periods of time thus giving minerals time to grow larger.
    • B.Fine grained (Aphanitic) texture
    • 1. All of the minerals are about the same size but are too small to see with the naked eye
    • a.Aphanititc texture develops when lavas cool quickly
    • i.Many small minerals develop, but lava cools so quickley there is no time for minerals to grow large.
    • C.Porphyritic Texture
    • 1.Minerala are of two sizes due to different rates of cooling.
    • a. Phaneritic- porphyritic texture
    • i. All minerals are visible, but some minerals are significantly larger.
    • b. Aphanitici-porphyritic texture
    • i. larger minerals in a matrix of smaller minerals.
    • ii. Slow rate of cooling then fast rate of cooling
    • a. some minerals formed from magmas as it slowly cooled the magma erupted onto the surface and cooked quickly
    • D. Glassy texture
    • 1. Lava cools instantly, no minerals are present
    • 2. Obisidian (volcanic glass)
    • 3.Pumice- light colored
    • 4.Scoria- dark colored
    • E. Pyroclastic texture
    • 1.Pyroclastic material forms when material is ejected explosively during a volcanic eruption.
    • 2. Range from dust and ash (very small) to lapilli and bombs
    • 3.Pyroclastic materials consolidate to form igneous rocks with pyroclastic textures
  4. Igneous Rocks Compositions
    • A. Bowens Reaction Series
    • 1.Bowen experimented how minerals cyrstallize from a magma
    • 2. As magma cools, minerals crystallize
    • 3.Different minerals cyrstallize at different temperatures
    • 4. Ideally, when a magma cools the first mineral to cyrstalliize is olivine, the last to cyrstallize is quartz
    • 5. Minerasl that crystalize at about the same temperature are found togethere in the same igneous rock
  5. Classification of Igneous Rock
    • A.Felsic(granitic) composition
    • 1.Rocks that are composed mostly of light colored minerals such as quartz and feldspar