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Task
 Research each of the three different kinds of rock: igneous, sedimentary, and
metamorphic.
1. Igneous rock –
Formation- Igneous rock is formed when magma cools and hardens. They form
below the ground when magma is trapped and cools (intrusive) or when lava
spills to the surface, when a volcano erupts and hardens at the surface (extrusive).
Composition – Igneous rock has 3 classifications of composition
1. Felsic (light color) Granite
2. Mafic (dark color) Basalt
3. Intermediate (intermediate color) Diorite
Texture- crsystal shape
Intrusive igneous rock forms slowly under the surface. The slow release of heat
allows larger crystals to form. They have large mineral grains with coarsegrained texture.
Extrusive igneous rock forms rapidly at the surface of Earth. The rapid loss of
heat does not allow large crystalline grain to form. They have small crystal grains
that are not easy to see.
Other cases where the loss of heat is altered in mid cooling time results in various
odd shapes of crystals. If heat loss is slow then rapid near the surface large
crystals are embedded inside with smaller ones on the outside. Or if heat loss is
extremely rapid then no crystal may be seen.
a. What determines whether an igneous rock will have large crystals or small
crystals? The time it takes to cool – how rapid the heat loss is. Rapid heat
loss makes small crystals, while slow heat loss gives larger crystals.
b. Name the three families of igneous rock. Felsic, mafic, intermediate
2. Sedimentary rock –
FormationClastic Sedimentary Rock – formed by rock fragments carried away from their
source by erosion. Over time the fragments become cemented into solid (Clastic)
rock
Chemical Sedimentary Rock – formed when minerals are dissolved in water.
Organic Sedimentary Rock – formed from the remains of organisms.
Features
Stratification (layering) –is caused by a change in the type of sediment being
deposited.
Ripple Marks and Mud Cracks – are caused by the action of wind or water on
sand.
Fossils- are the remains or traces of ancient plants and animals
Concretions- form when minerals precipitated from solutions build up around
existing rock particle. They appear as lumps or nodules.
a. How does clastic sedimentary rock differ from chemical sedimentary
rock? Clastic sedimentary rock are caused by particles of sediment that
cemented into a solid over time, while chemical sedimentary rock is rock
that was dissolved in water and has hardened as water evaporated.
b. What kind of sedimentary rock forms from the remains of decaying
organisms? Organic sedimentary rock
c. What term describes the remains or impressions of plant and animals in
sedimentary rock? Fossils
3. Metamorphic rock –
Formation
Contact Metamorphism – when rock near or actually touching hot magma are
metamorphosed by heat.
Regional Metamorphism – occurs when the movement of one tectonic plate
against another creates tremendous heat and pressure in the rocks at the plate
edge.
Classification – according to structure
Foliated Rocks – visible parallel bands of crystal.
Unfoliated Rocks – without visible bands of crystal
a. Explain the difference between a foliated structure and an unfoliated
structure? Foliated structre have visible parallel bands of crystal, while
unfoliated structure have no visible bands of crystals.
http://www.fi.edu/fellows/payton/rocks/create/index.html