Chapter 3: Igneous Rocks
Granite and andesite
Types of igneous rocks form at convergent plate boundaries
Grabbro and basalt
Types of igneous rocks form at divergent plate boundaries.
diorite, andesite, feldspars
Types of intermediate rocks and minerals
Grabbro, basalt, mostly ferromegnesian minerals
Types of mafic rocks and minerals
Peridotite, entirely ferromagnesian minerals
Types of ultramafic rocks and minerals
Silica rich, potassium rich, and sodium rich
What describes felsic rocks?
diorite
What is the name of the rock?
Gabbro
What is the name of this igneous rock?
basalt and gabbro
(blank) and (blank) are the predominant igneous rocks underlying the oceans.
Batholiths
(blank) are believed to form through the coalescence of numerous plutons, each representing a diapir of magma that worked its way up through the crust
mantle plumes
(blank) are hot material that rises or upwells within the mantle
Rhyolite; granite
(blank) is a fine-grained felsic igneous rock and (blank) is its coarse-grained equivalent.
Intrusion
(blank) is a general term for any body of intrusive rock. Specific names are based upon size, shape, and relationship to surrounding rock.
concordant
(blank) is a term used for a feature that is parallel to any planes or layering in the country rock
magma
(blank) is the term used for molten rock beneath the earths surface
Decompression
(blank) melting takes place when a body of hot mantle rock moves upward and pressure is reduced.
one or more minerals
A rock is a naturally occuring, consolidated material composed of (blank)
Sills are concordant with layers in the country rock; dikes are discordant.
What distinguished sills from dikes?
pyroclasts
What general term refers to the fragments that form from lava that is blasted out of a volcanic vent?
Temperature and pressure
What increases with increasing depth into the earth?
Crystals too small to be seen with the naked eye.
What property describes aphanitic igneous rocks?
Bowen's reaction series
A graph the shows the order in which minerals crystallize from a cooling magma
Quartz and potassium feldspar
According to Bowen's reaction series, the first minerals of a rock to melt as temperature increases will be (blank)
pegmatite
An extremely course grained rock, with crystals that range in size from a few cm to over a m in length, is called a (blank).
Divergent
Decompression melting is an important process at (blank) plate boundaries.
dissolved in the magma
In a magma chamber located several km below the surface, gasses would be (blank)
Geothermal gradient.
The rate at which temperature increases with depth beneath the surface of the earth is referred to as the (blank)
stock
The relatively small, isolated exposure of part of the batholith in this figure would be classified as a (blank)
any of the other kinds of rocks
The rock cycle shows that each of the three rock types can form from (blank)
crystalline
The rock has what type of texture?
Solidus
The temperature below which rocks are completely solid for any given depth on the geothermal gradient.
continuous and discontinuous
The two branches of Bowens reaction series
decompression melting
The type of melting that occurs at divergent plate boundaries
igneous
(blank) rocks form from molten rock that solidifies
Mafic
(blank) rocks have between 45-55% silica and relatively high contents of magnesium, iron, and calcium.
Peridotite
(blank), a coarse grained rock composed of olivine and pyroxene, is the most abundant ultramafic rock
Andesite
Coarse grained counterpart to diorite?
diorite and andesite
Intermediate igneous rock examples
glassy
Texture: has few, if any, crystal
ultramafic
A (blank) igneous rock is composed entirely or almost entirely of ferromagnesian minerals
sill
A (blank) is a concordant, tabular intrusive structure.
stock
A (blank) is a relatively small discordant pluton that has a surface exposure of less than 100 square kilometers
contact
A (blank) is a surface seperating different rock types.
dike
A (blank) is a tabular, discordant intrusive igneous structure.
volcanic neck
A (blank) is an intrusive structure apparently formed from magma that solidified within the throat of a volcano.
diorite; andesite
A coarse grained intermediate igneous rock is called (blank) and a fine grained intermediate rock is called (blank)
peridotitie
A coarse grained rock composed of olivine and pyroxene, the most abundant ultramafic rock.
pluton
A large body of coarse grained igneous rock that formed at considerable depth within the crust is called a (blank)
batholith
A very large (greater than 100 km) area of exposed plutonic rock is called a (blank)
magma cools and solidifies in the throat of a volcano
A volcanic neck forms when (blank)
ultramafic
An igneous rock that contains less than 45% silica is called (blank)
first slowly within the earth and then quickly after being erupted
An igneous rock that has a porphyritic texture suggest that the rock solidified (blank)
assimilation
As magma travels through the country rock, some of the country rock melts, changing the composition of the magma. This process is called (blank)
asthenosphere
At a divergent plate boundary, basaltic magma forms through the melting of (blank)
decompression of the mantle as it wells upward
At divergent boundaries, melting of the mantle to form basaltic magma occurs mainly due to (blank)
silicon, oxygen
Because magma contains a lot of (blank) and (blank), igneous rocks are composed mostly of silicate minerals.
diapirs
Blobs of magma that work their way up through the crust are referred to as (blank)
ultramafic to mafic to intermediate to felsic (increase in silica)
Bowen's reaction series shows that if the crystallizing minerals are removed from a melt as it cools, the magma compositiion can evolve from (blank)
Basalt
Coarse grained counterpart to gabbro?
Rhyolite
Coarse grained counterpart to granite?
Komatilite
Coarse grained counterpart to peridotite?
the magma cools slowly, giving minerals time to grow
Coarse grained intrusive igneous rocks have large crystals because (blank)
fractional crystallization
Differentiation of magma as it cools and minerals form is called (blank). It can occur through a number of processes, including crystal settling.
cracks and bedding planes in country rock
Dikes and sills form along (blank)
tabular, discordant structures of intrusive igneous rocks.
Dikes are (blank)
Hawaiian islands, Columbia plateau basalts (washington and oregon, Yellowstone caldera (wyoming)
Example of volcanic activity associated with mantle plumes
Gabbro, basalt
Examples of mafic rock.
lower the temperature at which granite melts
Experiments have shown that even small amounts of water will (blank)
Granite and rhyolite, diorite and andesite, gabbro and basalt, peridotite and komatilite
Fine grained igneous rocks and their coarse grained counterparts made of the same mineral composition.
partial melting of the lower crust
Geologists believe the large volumes of granite found in most continents are formed by (blank)
obsidian
Glassy textures form when lava cools extremely rapidly. An example of igneous rock that has a glassy texture is (blank)
Convection and conduction.
Heat from the Earths core is transported to the surface through the processes of (blank)
Expansion of gases, forming a bubble
How do vesicles form?
Breccia is made up mostly of larger pyroclasts.
How would a volcanic breccia be distinguished from a tuff?
scoria
If a basalt is extremely bubbly, it is classified as a (blank)
extrusive
If molten rock solidifies on the surface of the earth, it is a (blank) igneous rock.
andesitic
If you were to mix roughly equal amounts of a granitic magma with a basaltic magma, the resultant magma would be (blank) in composition.
hot spot
Igneous activity that occurs a long way from a plate boundary is referred to as a (blank). This activity is believed to be related to mantle plumes.
Texture and mineral composition
Igneous rocks are named based on what?
xenoliths
Igneous rocks can include fragments of other distinct rocks; these inclusions are called (blank)
intermediate
Igneous rocks with a chemical composition between that of felsic and mafic are classified as (blank) rocks
glassy
In an igneous rock with a (blank) texture, the atoms are not ordered into crystalline structures and thus there are no minerals present.
color
In fine grained rocks, individual minerals cannot be distinguished, and so the property of (blank) must be used to identify the rocks composition
geothermal gradient
In order for rocks to melt and form magma, the (blank) must intersect the zone of partial melting.
between 55 and 65 percent silica
Intermediate igneous rocks are composed of (blank)
flux melting
Melting of the mantle at convergent boundaries is believed to occur through the process of (blank)
Core
Most of the heat that contribute to the generation of magma comes from the very hot earths (blank)
Felsic (65% and more), intermediate (between 50 and 60), mafic (close to 50), ultramafic (less than 50)
Order of amount of silica in rocks.
mafic
Parital melting of the ultramafic mantle will usually produce a melt that is (blank) in composition
higher
Partial melting of the lower continental crust will produce a magma that is (blank) in silica content that the parent material.
their large crystals are easy to identify
Plutonic rocks are relatively easty to classify because (blank)
viscous
Rhyolite is not as common as granite because felsic magma is very (blank) and therefore cannot easily move toward the surface.
minerals
Rocks melt over a range of temperatures because they are made up of different (blank) that each have their own melting point
small size and proximity to the surface
Shallow intrusive bodies tend to be fine grained because they cool quickly, resulting from their (blank)
volcanic neck
Ship Rock in New Mexico, the central mountain in the picture, is an example of (blank)
crystalline
Texture: made up of interlocking crystals
water
The addition of (blank) significantly reduces the melting temperature of mantle rock.
vesicles
The cavities in this rock are called (blank)
crystal settling
The downward movement of minerals that are more dense than the magma is called (blank)
country rock
The inclined layers of sedimentary rock into which this magma has been intruded are referred to collectively as the (blank)
Composition, textures
The intrusive rocks granite and the extrusive rock rhyolite can have the same (blank) but will have different (blanks)
dikes
The lack of layering in the dark colored country rock in this image means that all of the pale colored intrusive structures would be classified as (blank)
dike
The low wall like ridge extending outward from Ship Rock in this image is an eroded (blank)
pressure
The melting point of a mineral tends to increase with increasing (blank)
mafic
The more of the mantle that melts, the more (blank) will be the composition of the partial melt.
granite
The most abundant intrusive igneous rock in the continental crust is (blank)
discontinuous branch
The order in which olivine, pyroxene, amphibole, and biotitie crystallize from a cooling magma is referred to as the (blank) of Bowen's reaction series.
Granite
The predominant igneous rock on other continents
differentiation
The process by which different ingredients separate from an originally homogeneous mixture is called (blank)
magma mixing
These rounded, dark colored blobs in a light colored granite are evidence for (blank)
batholith, granite
This figure shows an image of the Sierra Nevada (blank), which is composed primarily of the igneous rock (blank)
A) metamorphic B) igneous C) sedimentary
This figure shows how each of the three different types of rocks are formed at a convergent plate boundary. Match the regions labeled a to c with the rock types that are forming in them.
vesicular (looks a like a swiss cheese)
This rock displays a (blank) texture
granite, rhyolite, quartz, feldspar
Types of felsic rocks and minerals
rate of cooling and viscosity of magma
Two critical factors that determine crystal size during the cooling and solidification of igneous rocks
Frothy, glassy, vesicular
What accurately describes the pumice shown here?
Glassy, fragmental, crystalline
What are the three major groups of igneous textures?
The separation of elements from a magma through processes such as crystal settling.
What is the process of differentiation?
phaneritic
What is the term used for coarse grained igneous rocks?
It is a type of basalt, and it is highly vesicular
What is true of scoria?
Plate tectonics would stop; Earths minerals, water, and atmosphere would eventually be in equilibrium; the continents would erode down to sea level
What would happen if the Earths internal heat engine were to stop?
it is not parallel to the bedding in the country rock.
When a dike is described as discordant, this means (blank)
phenocrysts
When an igneous rock contains larger crystals that are enclosed in a groundmass of finer grained crystals, the larger crystals are referred to as (blank)
intrusive
When magma solidifies under the surface forming (blank) igneous rock , it may later be exposed after uplift and erosion remove the overlying country rock.
Intermediate and felsic
Which magma types are most commonly associated with subduction at convergent plate boundaries?
Biotite mica, olivine, and pyroxene
Which minerals will be most abundant in an igneous rock formed from a magma that is rich in iron, magnesium, and calcium?
Feldspars and quartz
Which minerals will be most abundant in an igneous rock that cooled from a magma rich in silica, potassium, and sodium?
quartz and feldspars
Which minerals will be most abundant in an igneous rock that cooled from a magma rich in silica, potassium, and sodium?
Plagioclase feldspar is a solid solution mineral, allowing substitution of sodium for calcium ions.
Why is the crystallization sequence of the plagioclase feldspars referred to as the continuous branch of Bowens reaction series?
fragmental
composed of broken pieces of igneous material