Geology Test 2 (Igneous)
What kind of melting do you expect at subduction zones?
Flux-induced melting
Dikes and sills are:
High-angle and low-angle igneous intrusions
Bowen's Reaction Series:
Shows that minerals in a cooling magma crystallize in a predictable order
Hot rock melt inside the Earth is called
magma.
Another name for fragmental texture is
pyroclastic
In the above diagram in Q.52, which of the following data sets represents an approximately accurate dataset that describes the pressure (kbar), temperature (°C) and depth (km) of a rock at point B?
50, 1700, 150
Extrusive igneous rock textures can be:
Aphanitic or glassy or fragmental texture
Which of the following words may be used to describe portions of rock with porphyritic texture?
Aphanitic, Phenocrysts, Groundmass
Which of the following melt compositions do you expect to travel long distances?
Basalt melts
Which of the following pairs of minerals are part of the continuous reaction series in Bowen's Reaction Series?
Ca-rich plagioclase and Na-rich plagioclase
Two magma chambers of similar size are undergoing crystallization. Chamber A is tabular. Chamber B is spherical. Which chamber cools faster?
Chamber A
Two magma chambers of similar size are undergoing crystallization. Chamber X is 10 km below the Earth's surface. Chamber Y is 50 km below the Earth's surface. Which chamber cools slower?
Chamber Y
All phaneritic textures are:
Coarse-grained, Derived from magma, Cooled slowly
Give an example of a LIP in continental US
Columbia River Flood Basalts
What kind of melting do you expect in a continental rift tectonic setting?
Decompression melting
What kind of melting do you expect just under a mid-ocean ridge?
Decompression melting
Give an example of a place currently undergoing continental rifting.
East African Rift
Pyroclastic flow occurs in:
Felsic melts flows & Extrusive settings
All aphanitic textures are:
Fine-grained, Derived from lava, Cooled faster
A coarse-grained magmatic igneous rock with 65% SiO2 and containing minerals like quartz, K-feldspar may be called:
Granite
Porphyritic rocks are named for the size of:
Groundmass grains
Give an example of a location experiencing hotspot-induced volcanism?
Hawaii
Intra-plate volcanism is seen at:
Hotspots
A dike intrudes into:
Igneous rock, Sedimentary rock, Metamorphic rock
A phaneritic texture is one in which:
Individual crystals can be seen with the naked eye
An aphanitic texture is one in which:
Individual crystals cannot be seen with the naked eye
Porphyritic textures indicate:
Initial slow cooling and then fast cooling
As a mantle rock moves from A to B in this diagram below, what happens?
It begins to melt via decompression
In the above diagram in Q.52, Point A represents a rock that fits with which of the follow descriptions?
It has a pressure of ~ 100,000 bars
Flood basalts are characteristic of:
LIPs
LIP is
Large Igneous Provinces
What kind of igneous rocks do you expect at mid-ocean ridges?
Mafic fine-grained
Composition of the earth's mantle is:
Mafic to ultramafic
Why does molten rock move upward through the Earth's mantle?
Molten rock is less dense than the surrounding solid rocks
Which of the following rocks display a stunningly black glassy texture?
Obsidian
Which of the following minerals crystallize via the discontinuous reaction series?
Olivine, Pyroxene, Amphibole
All intrusive igneous rocks have:
Phaneritic texture
A vascular texture is one in which:
Pores are abundant
List the 4 tectonic settings where igneous activity occurs:
Subduction zones, Midocean ridges, Continental rifts, Hotspots
Which of the following rocks is not derived from an igneous rock melt?
Tuff
An igneous rock containing <45% SiO2 is called:
Ultramafic rock
Which of the following melt compositions are arranged in the order of increasing viscosity?
Ultramafic<mafic<Intermediate<Felsic
Which of the following melt compositions are arranged in the order of increasing volcanic explosivity?
Ultramafic<mafic<Intermediate<Felsic
Vesicles in vesicular textures are remnants of:
Volatile passages in an igneous rock
Fragmental texture is formed from:
Volcanic ash and Volcanic rock debris
In a flux-induced melting, which of the following can act as flux?
Water vapor, Carbon-dioxide, Sulphur dioxide
A magma that is rich in volatiles is called:
Wet magma
List 3 tectonic and/or mantle processes that trigger decompression melting.
continental rifting, sea floor spreading, mantle plume
Mafic igneous rocks tend to have
dark_-color shades.
A porphyritic texture is one in which
individual crystals are a mix of coarse and fine-grained crystals
Felsic magma:
is more viscous than mafic magma
Hot rock melt on the Earth's surface is called
lava
Felsic igneous rocks tend to have
light_ -color shades.
What is the primary factor that keeps the mantle rocks from melting at very high temperatures of ~3000 °C?
overburden pressure
Coarse-grained crystals in porphyritic textures are called
phenocrysts