Chapter 3 - Igneous Rocks Flashcards
If a body of magma becomes more felsic, its viscosity will:
a. increase
b. decrease
c. stay the same
a. increase
Obsidian has a _________ texture.
a. glassy
b. fine-grained
c. coarse-grained
d. vesicular
e. porphyritic
a. glassy
The Sierra Nevada Mountains are an example of a pluton called a:
a. laccolith
b. stock
c. batholith
d. dike
e. sill
c. batholith
Think back to Bowen’s Reaction Series to respond to this. If a body of magma is subjected to fractional crystallization, the rock that results is expected to be:
a. identical in chemical composition to the magma
b. more mafic than the magma
c. more felsic than the magma
c. more felsic than the magma
Magma that might have cooled slowly to produce a diorite is instead erupted at Earth’s surface. It would chill rapidly and produce a(n) ________.
rhyolite
granite
basalt
andesite
andesite
(T/F) Peridot is the gemstone variety of biotite.
False
In accordance with Bowen’s reaction, this mineral would crystallize at the highest temperature.
a. quartz
b. amphibole
c. olivine
d. feldspar
c. olivine
(T/F) Peridotite is an ultramafic igneous rock.
True
Most commonly felsic igneous rocks:
a. contain more iron and magnesium than intermediate rocks
b. are lighter in color than mafic rocks
c. are darker in color than mafic rocks
d. are found in oceanic crust
b. are lighter in color than mafic rocks
(T/F) It is impossible for granite to form from magma rising to the surface at a mid-ocean ridge.
True
All other factors being equal, intrusive rocks that form deep within Earth ___________ than intrusive rocks that cool near the surface.
a. are more felsic
b. contain smaller proportion of volatiles
c. cool more rapidly
d. cool more slowly
d. cool more slowly
Magma composition can change through:
a. crystal settling
b. assimilation
c. partial melting
d. all these
d. all these
(T/F) Granite and rhyolite have the same chemical composition but different textures.
True
🔴 As compared to coarse grained igneous rocks, all fine-grained igneous rocks:
a. solidify at lower temperatures
b. solidify at higher temperatures
c. cool and solidify more slowly
d. cool and solidify more quickly
a. solidify at lower temperatures?
As a magma composition changes from mafic to felsic, which of the following elements increases?
a. calcium
b. magnesium
c. iron
d. silicon
d. silicon
(T/F) Ferromagnesian minerals form at the lowest temperatures.
False
An igneous rock with a mixed texture of coarse-grains (phenocrysts) surrounded by fine-grained matrix is called (the chocolate chip texture rock):
a) pyroclastic
b) porphyritic
c) glassy
d) vesicular
b) porphyritic
Which of these minerals is on the Continuous side of Bowen’s Reaction Series?
a. olivine
b. quartz
c. plagioclase feldspar
d. muscovite
c. plagioclase feldspar
Which one of the minerals is not one of the eight most common elements found in Earth’s crust?
a. silicon
b. oxygen
c. carbon
d. aluminum
c. carbon
A sill is:
a. a sheet-like intrusion that lies parallel to surrounding layers of sedimentary rock
b. a cooled layer of lava
c. an intrusion formed within the magma chamber of a volcano
d. a sheet-like intrusion that cuts across preexisting rock layers.
a. a sheet-like intrusion that lies parallel to surrounding layers of sedimentary rock
🔴 Which igneous texture is characterized by two distinctively different crystal sizes?
a. fine-grained
b. coarse-grained
c. porphyritic
d. glassy
c. porphyritic
Which of these tectonic settings result in decompression melting?
a. subduction zone
b. divergent or spreading center
b. divergent or spreading center
The formation of magma within the Earth is NOT caused by which of the following:
a. decompression (drop in pressure)
b. addition of volatiles (like water vapor)
c. transfer of heat from adjacent magma or very hot rocks
d. loss of volatiles to the atmosphere
d. loss of volatiles to the atmosphere
(T/F) The Sierra Nevada Mountains are an example of a pluton called a laccolith.
False
(T/F) Ferromagnesian minerals form at the lowest temperatures.
False
Which of the following pairs of intrusive (Phaneritic) and extrusive (Aphanitic) rocks have the same chemical composition?
a. rhyolite and diorite
b. diorite and granite
c. gabbro and basalt
d. gabbro and andesite
e. granite and gabbro
c. gabbro and basalt
(T/F) Sills are discordant; dikes are concordant.
False
On the discontinuous side of Bowen’s reaction series, what mineral crystallizes at the coolest temperature.
a. quartz
b. muscovite
c. amphibole
d. pyroxene
a. quartz
The geotherm is the rate of change of:
a. pressure with depth of the Earth’s interior
b. temperature with depth in Earth’s interior
c. temperature with altitude in Earth’s atmosphere
d. temperature with latitude on Earth’s surface
b. temperature with depth in Earth’s interior
