Practice Problems
Problem W6.1. Metamorphic Rock from a Rifle. In 1801, Sir James Hall made a
metamorphic rock. He put powdered calcium carbonate (calcite, CaCO3) in the breech of
a gun. The breech was a chamber in firearms of that time where explosive gunpowder
was detonated to expel the bullet. He then sealed the breech. Placing the gun in a furnace,
Hall heated the gun and its contents, while the sealed chamber kept the calcium carbonate
under pressure. In time, the powered material fused into one solid mass.
WQ6.1. What is the rock name for this human-made metamorphic rock?
_________________________
Problem W6.2. Metamorphic Grade.
WQ6.2. What four rocks can be derived when regional metamorphism acts upon shale?
(Arrange in increasing order of metamorphic grade, from 1 to 4)
1 _____________ 2 _____________ 3 ______________ 4 ______________
WQ6.3. Do the higher-grade rocks in this sequence typically have smaller or larger
crystals than the lower-grade rocks?
smaller larger
Problem W6.3. Fracturing Quartz Sandstone versus Fracturing Quartzite.
WQ6.4. Quartz sandstone, if broken with a hammer, generally will break:
___ around its sand grains
___ through its sand grains
WQ6.5. Quartzite rock, if broken with a hammer, generally will break:
___ around its crystals
___ through its interlocking crystals
Problem W6.4. Metamorphic Terranes. A terrane is a body of rock that is bounded by
faults. One of the first places on Earth where metamorphic terranes were studied was the
highlands of Scotland. Figure WS6.1 shows the rocks of Scotland, divided into
metamorphic zones (facies). The zones are separated by lines (isograds), which show the
first appearance of key metamorphic minerals.
WQ6.6. Figure WS6.1 suggests that metamorphic grade increases in this area in what
compass direction?
South
Southwest
Northwest
Northeast
None of these
WQ6.7. Suppose you start walking across Scotland, straight from Inverness to Glasgow.
You would be walking over metamorphic rocks that reflect a change in grade. As your
trip progressed, the rocks under your feet would change to
___ (a) rocks of higher pressure and temperature
___ (b) rocks of higher metamorphic grade
___ (c) rocks of higher metamorphic facies
___ (d) rocks of lower pressure and temperature
Figure WS6.1 Metamorphic zones of Scotland, showing the grade of rocks.
(Map after Kennedy, 1948)
Problem W6.5. Type of Metamorphism. Figure WS6.2 shows the subduction of an
oceanic plate beneath a continental plate. Western South America is experiencing this
tectonic regime today.
WQ6.8. In Figure WS6.2, identify the zone or facies of metamorphism that most likely
would occur in each of the five numbered locations. (Refer to your lab manual, Figure
6.2, for conditions and names of facies.)
1. _______________________________________________________
2. _______________________________________________________
3. _______________________________________________________
4. _______________________________________________________
5. _______________________________________________________
Figure WS6.2 Tectonic regimes and metamorphism.
Problem W6.6. Inferring Temperature and Pressure Conditions. Imagine you are
studying a metamorphic rock and find crystals of kyanite, andalusite, and sillimanite
within it. All three of the minerals appear to be fully stable.
WQ6.9. Referring to the phase diagram of kyanite, andalusite, and sillimanite in Figure
6.1 of your lab manual, what are the most likely pressure and temperature conditions for
the formation of your rock?