- Southwestern Illinois College
- Earth Science
- Earth Science 101
- Chapter 2
Last Modified: 2014-06-11
The 3 types of rocks are:
Igneous, Sedimentary and Metamorphic
The Rock Cycle
shows the interrelationships among the 3 rock types
Earth as a system : the rock cycle
The full cycle does not always occur due to
shortcuts or interruptions
~Sedimentary rock melts
~Sedimentary rock is weathered
~Igneous rock is metamorphosed
~Metamorphic rock is weathered
These are examples of shortcuts in the rock cycle
is a process in which rocks are broken down by water, air and living things.
is weathered pieces of Earth's elements.
"Formed by Fire"
forms as magma cools and crystallizes
Plutonic or Intrusive
Igneous rock formed inside the Earth
Volcanic or Extrusive
Rock formed on the surface.
Formed from Lava
How is Lava different from Magma?
Lava is above ground and without gas
Molten material consists of mainly what 2 elements?
Silicon and Oxygen
also lesser amounts of aluminum, iron, calcium, sodium, potassium, magnesium and others.
Magma also contains ______, particularly _________.
gases, water vapor
What happens to most magma?
It loses its mobility before reaching the surface and crystallizes deep below the surface.
Igneous rocks formed at depth are called
Intrusive or Plutonic
Intrusive/plutonic igneous rock remains at depth unless:
~portions of the crust are uplifted ~and the overlaying rocks stripped away by erosion
Exposures of intrusive igneous rock occur in many places, such as
~Mount Washington, New Hampshire
~Stone Mountain, Georgia
~ Mount Rushmore, Black Hills of South Dakota
~ Yosemite National Park, California
How or why does a magma body rise to the surface?
Because it is less dense than the surrounding rocks.
Molten rock that reached the surface.
1980 eruption of Mount Saint Helens was caused by?
Magma explosively ejected from vents on Earth's surface.
What forms when molten rock solidifies on the surface?
Extensive or Volcanic Igneous rocks
Extrusive igneous rocks are abundant in western portions of the Americas, including:
~volcanic cones of Cascade Range
~extensive lava flows of the Columbia Plateau
Many oceanic islands, including the Hawaiian Islands, are composed almost entirely of _________ ______ _____.
volcanic igneous rocks
Ions arranged into order patterns describes what process?
Crystallization of magma.
What 3 properties determine crystal size?
1. The rate of cooling
2. Composition of a magma
3. Amount of dissolved gases
Magma at a slow rate of cooling results in the formation of
Magma at a rapid rate of cooling results in the formation of
small or microscopic crystals
If magma cools at a very rapid rate, results in formation of
glass, such as Obsidian.
Classification of igneous rock is based on ______ and ________.
the rock's texture and mineral constituents.
Texture refers to what?
Size and arrangement of crystals
What are the 4 basic igneous rock textures?
1. Fine grained (fast cooling)
2. Course grained (slow cooling)
3. Porphyritic (2 sizes and 2 rates)
4. Glassy (very fast cooling)
If igneous rock exibits a fine grained texture, what do we know?
~rapid rate of cooling of lava or magma
~may contain vesicles (holes from gas bubbles)
What is a Vesicular Texture?
~has holes in it from gas bubbles that escaped
~Igneous rock, lava or magma
~very light b/c the holes
If course grained igneous rock, then we know....
slow rate of cooling, large crystals identified w/o microscope
What is Porphyritic Texture?
~large crystals imbedded in a matrix of smaller crystals.
Minerals form at different temps, and also at different rates.
What is Bowen's Reaction Series?
It shows the order of mineral crystallization.
~influenced by crystal settling in magma
What is the 1st mineral to crystallize from a body of magma, as discovered by Bowen?
Bowen found further cooling results in the formation of _______ as well as _________.
pyroxene, plagioclase feldspar
At intermediate temperatures, Bowen found the minerals ______ and ________ begin to crystallize.
amphibole and biotite
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