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