Download Answers to Chapter 4 (Rocks) Study Guide 1. The (3) types of rock

Answers to Chapter 4 (Rocks) Study Guide
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The (3) types of rock are:
a. Igneous rock - forms from the cooling of molten rock (can be magma or lava). Depends on where
it is formed (beneath or at earth’s surface). They are hard, dense, and durable. Used for tools
and building materials. Ex. Granite, basalt, obsidian.
b. Sedimentary rock – forms from sediment that has been weathered, eroded, and deposited by
agents (wind, water, etc.) in layers. These layers are compacted then cemented together by
minerals that dissolve in water and crystallize to glue sediments together. Many are soft and
able to be cut in slabs. They are also used for building materials & wall coverings. Ex. Shale,
sandstone, conglomerate, limestone.
c. Metamorphic rock – rock has been changed by heat and/or pressure deep beneath Earth’s
surface. Mineral composition, texture, or crystal structure can be changed. They can form from
any type of rock. Marble and slate are two examples. They can be cut into thin slabs and able to
be molded and polished for smooth finishes. Used for buildings and statues.
The (3) ways in which magma is formed are:
a. When hot rock rises from deep beneath Earth’s surface, then pressure is released and then
minerals can melt
b. When rock is heated, minerals within them can melt
c. When rock changes composition and comes in contact with water or other fluids, melting point
of the rock lowers and allowed to melt
The (2) ways in which igneous rocks are classified are:
a. Intrusive igneous rock – rock formed from the cooling and solidification of magma (beneath the
Earth’s surface). These rocks cool slowly and usually have large crystals and a coarse-grained
texture.
b. Extrusive igneous rock- rock formed from the cooling of lava (magma which erupts onto Earth’s
surface). These rocks either cool quickly (small crystals – fine-grained) or instantaneously (no
visible grain – glassy).
The (3) ways in which sedimentary rocks are classified are:
a. Clastic sedimentary rock – made of fragments of rock or minerals cemented together by mineral
solutions made of quartz or calcite. They can be coarse-grained, medium-grained, or finegrained. (Ex. Conglomerate, sandstone, shale).
b. Organic sedimentary rock – forms from remains of plants or animals that once lived in the ocean.
Ex. Coal forms underground from partially decomposed plant material buried beneath sediment.
Over millions of years, heat & pressure change it into coal.
c. Chemical sedimentary rock – forms from solutions of dissolved minerals and water. The minerals
crystallize and create a chemical rock. Ex. Halite – forms when sodium & chlorine ions in water
become so concentrated that they crystallize from the solution.
The (2) ways metamorphic rocks are classified are:
a. Foliated – rock that has mineral grains which are arranged or aligned in bands or planes. Intense
pressure and slight heat very deep beneath the surface causes this change in the rock. Ex. Slate,
gneiss
b.
Nonfoliated – rock that has mineral grains which are not arranged or aligned in bands or planes.
During metamorphism the crystal size or mineral composition undergoes change. Ex. Marble,
quartzite.
6. All rocks are classified by:
a. Composition, texture, and origin.
7. Forces that help shape Earth’s surface include:
Weathering, erosion, deposition, heat & pressure, uplift, deformation
8. When magma cools slowly, mineral crystals have more time to grow. They will be larger and the texture
will be coarser. Thus, producing an intrusive igneous rock.
9. When lava cools instantly, there is no time for crystal formation. The rock will show no visible grain and
will have a glassy texture.
10. When lava cools fairly quickly (but not instantaneously), small crystals will form. This creates an extrusive
igneous rock with fine-grained texture.
11. See pgs. 92-94 of your textbook. Be sure to pay attention to the forces that drive the cycle and the end
products.
Relevant Vocabulary & Definitions
Foliation, nonfoliation, extrusive and intrusive igneous rock (all defined above).
Texture – appearance or quality of rock based on size, shape, and position of grains.
Composition – chemical makeup of a rock that identifies the minerals or other materials that make up a rock.
Stratification – process by which sedimentary rocks are arranged in layers
Strata – layers of rock
Forces that create rock –
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Weathering – agents such as water, wind, ice, and heat break down rock into fragments or
sediment which help to form sedimentary rock
Erosion – movement of sediment from its source to a new area. Agents such as wind, gravity,
ice, and water aid in this process.
Deposition – process by which sediment is dropped and comes to rest (settles) elsewhere
Heat & pressure – layers of earth squeeze sediments below. If temperature and pressure are
high enough, sedimentary rock can change to metamorphic rock and the rock cycle will come
into play
Uplift – movement within Earth that causes rocks inside to come to the surface. This is when
weathering, erosion, and deposition act on the rocks.
Deformation – a change in the shape of a rock caused by a force placed on it (tilting, bending,
etc.)
Rock – a naturally occurring solid mixture of one or more minerals, rock fragments, or organic matter.