Download ROCKS Rocks are cohesive solids composed of one or more minerals

ROCKS
Rocks are cohesive solids composed of one or more minerals (and mineral
materials, such as glass). There are three categories of rocks:
(a) Igneous rocks are formed by the solidification and crystallization of a
cooling magma. Plutonic igneous rocks form from magmas that cool
slowly at depth and are typically coarse-grained (granite). Volcanic
igneous rocks form at or very close to the earth’s surface, and their rapid
cooling and solidification usually result in fine-grained textures( basalt)
(b) Sedimentary rocks are formed from sediments at low temperatures.
Clastic sedimentary rocks are formed from fragments of preexisting rocks;
examples include sandstone, shale, and conglomerate. Chemical
sedimentary rocks are formed by direct precipitation of minerals from
solution; examples include limestone and rock salt. Bioclastic sedimentary
rocks form from shells (coquina) and plants (coal).
(c) Metamorphic rocks are formed by the recrystallization of preexisting
rocks that were subjected to heat and/or pressure. Foliated rocks display
banding and distorted structure (gneiss, slate,schist). Some are nonfoliated (marble, quartzite). Metamorphism can occur over a large
associated with mountain building (regional metamorphism) or when
magma comes in contact with pre-existing rocks (contact metamorphism)
All rocks are transformed over time into new rocks through various geologic
processes. This concept of interrelation among the different types of rocks is
known as the rock cycle.
VOCABULARY
Igneous
texture
crystallization
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magma
lava
intrusive (plutonic)
extrusive (volcanic)
granite
basalt
sediment
sedimentary
compaction
cementation
fossils
clastic sedimentary
chemical sedimentary
bioclastic/biochemical
metamorphic
contact metamorphism
regional metamorphism
strata
Multiple Choice
1. Which of the following is a good example of a chemical sedimentary rock?
a. sandstone
b. basalt
c. marble
d. limestone
2. An example of a plutonic igneous rock is
a. basalt.
b. obsidian (volcanic glass).
c. granite.
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d. sandstone
3. All of the following are examples of clastic sedimentary rocks except
a. conglomerate.
b. shale.
c. sandstone.
d. rock salt
4. Metamorphosed limestone is called
a. slate.
b. gneiss.
c. marble.
d. quartzite.
5.Igneous rocks are classified based on their
a.texture
b.chemical composition
c.color
d.weight
6.The two most abundant igneous rocks are
a.andesite and diorite
b.rhyolite and andesite
c.granite and basalt
d.none of the above
7.Sedimentary rocks are formed by
a.assembling of sediment grains layer by layer and subsequently by a process of
burial, compaction and cementation of layers
b.from the lava flow in a horizontal direction
c.melting of a rock by metamorphism and forming another metamorphic rock
d.none of the above
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8.The sedimentary rocks composed of fine, clay sized particles are called
___________ while those consisting of sand grains are called ______________
a.siltstone; sandstone
b.siltstone; shale
c.shale; sandstone
d.conglomerate;breccia
9.Contact metamorphism occurs when
a.metamorphism takes place within the sedimentary layer at the bottom of the
ocean
b.metamorphism takes place between two types of sedimentary rocks
c.metamorphism takes place over a vast region
d.magma comes in contact with pre existing rocks
10. Fossils are most common in
a.igneous rocks
b.metamorphic rocks
c.sedimentary rocks
d.minerals
ANSWERS
1. D
2. C
3. D
4. C
5. A
6. C
7. A
8. C
9. D
10. C
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