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