Earth Science Rocks

Topics: Sedimentary rock, Igneous rock, Rock Pages: 2 (299 words) Published: January 24, 2000
The 8 most
common elements in the earth's crust are Oxygen,
Silicon, Aluminum, Iron, Calcium, Sodium,
Potassium, & Magnesium. They compose 98.5%
of the total crust. A mineral occurs naturally, is a
soli, inorganic, has chemical composition and a
crystalline structure. Native minerals are single
elements. Compounds are 2 or more. There are
more compound than native. You can identify
minerals by color, streak, luster, hardness,
cleavage, and fracture. Minerals form by magma
erupting and forming lava then cooling. They can
also form by evaporation of water containing
dissolved ions. Silicates are the most common
group of minerals found in the earth's crust. The
structure of minerals are orderly. They form
crystalline. A crystalline has flat faces and smooth
surfaces. Igneous rocks are formed from magma.
If they are intrusive (plutonic), they have large
crystals and cooled slowly. If they are extrusive,
they cool quickly, have fined grain. The scheme
for igneous rock identification is based on texture,
color, composition, and density. Sedimentary
rocks are the 2nd step in the rock cycle. They are
composed of bits and pieces of rock that have
been watered by rain, water, and other things.
They compress and cement on top of each other
forming layers. When the water evaporates, the
sediments are left behind and forms a new rock.
This rock is either clastic (formed from igneous
rock) or organic (formed from living remains). The
other type of sedimentary rock is chemical which
is formed by the evaporation of water and the
precipitation on sediments form a new rock.
Metomorphic rock is the recrystalization (change
w/o melting) of rocks under extreem heat and
pressure. Regional metamorphism occurs over
large arieas where mountain building has taken
place. Comtact metamorphism occurs when
molten magma comes into contace w/ sourounding
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