CHS GEOLOGY: HW #6 Rock Review
Name:_________________ Period:____
1. Collisions between Earth’s plates push rock down toward the heat of Earth’s _______________ .
2. As the rock is buried deeper in the crust, _____________
as well as heat increases on the rock.
3. The rock is squeezed so tightly that the appearance,____________________
, and crystal structure of the
rock’s minerals change, creating metamorphic rock.
4.
describes the thin, flat layering found in most metamorphic rocks.
5. Describe a situation in which heat can change rock to metamorphic rock.
6. What characteristics do geologists use to classify metamorphic rocks?
7. Give examples of how two different metamorphic rocks are used.
Tremendous pressure and high temperatures can change any rock into metamorphic rock. This process often occurs near
plate boundaries. There, pressure builds as one plate collides with another. In addition, hot magma flows upward into rock
near these boundaries. Such intense conditions change one kind of rock into another, such as shale, a sedimentary rock
into slate, a metamorphic rock. But what happens if the pressure and temperature continue to increase after shale
becomes slate? Look at Figure 1 below. Slate changes into schist, and schist changes into gneiss.
Gneiss and schist are the most common metamorphic rocks. Gneiss is a foliated rock
usually composed of quartz and feldspar. Schist is also foliated, but its mineral
composition varies. The terms gneiss and schist actually describe certain textures of
metamorphic rock. That’s why both shale and granite can change into gneiss, and
both granite and basalt can change into schist. Figure 2 shows common metamorphic
rocks to the right. The rocks on the left are igneous and sedimentary rocks. The
arrows represent pressure and temperatures.
1. Using a sample of Shale, Slate, Schist and Gneiss, observe and sketch each rock
on the highest setting using the dissecting microscopes.
.
Shale
Slate
Schist
Gneiss
2. What causes shale to change into slate?
4. What happens to the slate if these conditions increase?
5. How do tremendous pressures and high temperatures affect limestone?
6. How does metamorphism affect basalt?
7. What rocks can change into schist?
8. How does increased metamorphism affect schist?
If the statement is true, write true. If the statement is false, change the underlined word
or words to make the statement true.
1.
Metamorphic rocks are foliated if their mineral grains are arranged randomly.
2.
Marble is often used in sculpture because its even color allows it to be carved into
complex and detailed shapes.
3.
Heat and pressure change the sedimentary rock shale into slate.
4.
Metamorphic rock can form out of other metamorphic rock.
5.
The deeper a rock is buried in the crust, the greater the pressure on that rock.
Fill in the blank to complete each statement.
6. The metamorphic rock
usually forms when limestone is subjected to heat and pressure
deep beneath the surface.
7. Because the foliated metamorphic rock
splits easily into flat pieces, it is used for roofing
material.
8. Any rock formed when another rock is changed by heat or
is a metamorphic rock.
9. Geologists classify metamorphic rocks according to the
of the grains making up the rocks.
10. Quartzite forms when the quartz particles in
recrystallize.
Igneous Review
Igneous rocks crystallize from a cooling silicate melt (magma or lava). They are composed of intergrown crystals of
minerals such as quartz, feldspars, micas, amphiboles, pyroxenes, and olivine. Felsic igneous rocks are silica rich
and contain abundant potassium feldspar and quartz. Felsic igneous rocks are light in color. Mafic igneous rocks
are iron and magnesium rich and contain abundant pyroxene, and calcium rich plagioclase feldspar. Mafic igneous
rocks are dark or black in color. Extrusive, or volcanic, igneous rocks cool and crystallize quickly at the Earth's
surface resulting in very small, microscopic crystals. Intrusive, or plutonic, igneous rocks cool and crystallize very
slowly beneath the Earth's surface allowing large, visible crystals to grow. Obsidian, volcanic glass forms where lava
cools so quickly (e.g., due to quenching in water) that crystals with their orderly arrangement of atoms do not have
enough time to form.
1. What is the difference between rhyolite and obsidian? Which do you think cooled more slowly and why?
2. Which rocks are mafic? From the reading above, why are mafic rocks darker than felsic rocks?
3. How are extrusive and intrusive rocks different from each other? What are they also known as (their other
names)?
4. Which types of rocks would you expect to find at Mt. Hood? Why?
5. The Columbia Gorge is primarily made up of Basalt. What does that tell you about how the Gorge formed?
6. Why doesn’t obsidian have any crystal structure?
Sedimentary Review
Sedimentary rocks are types of rock that are
formed by the deposition of material at the Earth's surface
and within bodies of water. Sedimentation is the collective
name for processes that
cause mineral and/or organic particles (detritus) to settle
and accumulate or minerals to precipitate from a solution.
Particles that form a sedimentary rock by accumulating are
called sediment. Before being deposited, sediment was
formed by weathering and erosion in a source area, and
then transported to the place of deposition
by water, wind, ice, mass movement or glaciers which are
called agents of denudation.
The sedimentary rock cover of the continents of
the Earth's crust is extensive, but the total contribution of
sedimentary rocks is estimated to be only 8% of the total
volume of the crust. Sedimentary rocks are only a thin
veneer over a crust consisting mainly
of igneous and metamorphic rocks. Sedimentary rocks are
deposited in layers as strata, forming a structure
called bedding. The study of sedimentary rocks and rock strata provides information about the subsurface that is useful
for civil engineering, for example in the construction of roads, houses, tunnels, canals or other constructions. Sedimentary
rocks are also important sources of natural resources like coal, fossil fuels, drinking water or ores.
1. Sediments form ____________________________ by the process of _________________________
_________________________________________________________________________________.
2. Sedimentary rocks can form _______________ , _______________ and _______________ rocks.
3. Which process changes sedimentary rock into igneous rock? ________________________________
4. Which process changes metamorphic rock into sedimentary rock? ____________________________
_________________________________________________________________________________
5. Compaction & cementation of sediments forms ______________________________________ rocks.
6. Subjecting sedimentary rocks to extreme heat & pressure forms ________________________ rocks.
7. Deposition and burial of sediments forms __________________________________________ rocks.
8. For weathering & erosion to occur, what process will the rock usually go through first or at the same
time? ____________________________________________________________________________
9. Can sedimentary rock form directly from metamorphic rock? Explain your answer.
10. What are five ways mentioned in the reading above that sediment can be transported? ___________
________________________________________________________________________________
11. What percentage of crust is sedimentary rock? Why do you think this is?_______________________
_________________________________________________________________________________
_________________________________________________________________________________
12. Why do you think sedimentary rocks form only a thin veneer (thin covering) over the crust? Explain in
detail! ____________________________________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________