Geology - Exam 2

pluton or intrusion

A ___________________, is cooled, emplaced magma into preexisting rocks

volcanic ash

Which type of volcanic hazard can decrease global temperatures?

Large igneous provinces

cover a large area on continents with mafic lava

Rhyolitic

type of magma that has the highest viscosity

felsic lava

1 percent of lava is

intermediate lava

10 percent of lava is

mafic lava

90 percent of lava is

an accessory mineral

A mineral that makes up a relatively small portion of the total rock composition

the color of the mineral in powdered form

A mineral's streak is _________.

intrusive; below the surface

A phaneritic texture is characteristic of a(n) __________ igneous rock that cooled __________.

fracture

Absence of cleavage when a mineral is broken

Quartz

According to Bowen's Reaction Series, __________ is one of the first minerals to melt, but last to crystallize.

the mantle and crust

As a result of partial melting, magma originates in __________.

the introduction of water

At a subduction zone, melting is triggered by _____.

Dark (Ferromagnesium) Silicates

Contain iron and/or magnesium in their structure, Generally dark in color, Have a specific gravity between 3.2 and 3.6

the basic unit cell of a mineral

Crystal habit is the shape that a mineral develops by the repetition of __________.

Igneous

Crystallization of molten rock will produce ________ rocks.

Solid, naturally occurring, generally inorganic, defined chemical composition, crystalline structure.

Define the five criteria a substance must meet in order to be considered a mineral.

iron (Fe), Calcium (Ca), and Magnesium (Mg)

Depleted in the melt:

potassium (K), Sodium (Na), and Silicon (Si)

Enriched in the melt:

intrusive and extrusive

Environment of cooling, and ultimately cooling rate, with respect to Earth's surface

eruption columns

Eruptions expel particles of fragmented lava and gases at supersonic speeds that evolve into _________________

Granite, Rhyolite, Obsidian, Pumice

Felsic Igneous Rocks

Light (Nonferromagnesium) Silicates

Generally light in color, Have a specific gravity of approximately 2.7, Contain varying amounts of aluminum, potassium, calcium, and sodium, Lacking iron and magnesium

The subducting slab drives water and carbon dioxide into the mantle, which reduces the temperature at which it melts, allowing mantle rock to melt and rise.

How is magma generated along convergent plate boundaries

Subduction zones/introduction of water, decompression melting, hot spots/other magma as a source of heat.

If the Earth's mantle is largely solid rock, how does magma form within this layer?

greater silica; lower melting temperature

Igneous rocks of felsic composition have __________ and __________ relative to mafic igneous rocks.

the melting temperature of mantle rocks to decrease

In a subduction zone, water driven from subducted oceanic crust causes __________.

Minerals will often form in cramped spaces, i.e., within pores or fractures of other rock.

In nature, why is it rare to observe minerals expressing their true crystal habits?

the bonding of the silicon-oxygen tetrahedra within the mineral.

In silicate minerals, the type of cleavage or fracture is influenced by:

andesite and diorite

Intermediate Igneous Rocks

density

Mass per unit volume

Batholiths and Laccoliths

Massive Intrusive Bodies:

Decompression melting

Melting occurs at higher temperatures with increasing depth

be generally inorganic in origin

Minerals must be solid, have an orderly atomic structure, have a recognized chemical composition, be naturally occurring, and __________.

Polymorphs

Minerals with the same composition but different crystalline structures

Ring of Fire

Most active volcanoes are found along the circum-Pacific

divergent

Most magma on Earth is produced at ___ plate boundaries.

CaCO3

Most marine organisms produce the mineral substance ________, which will later become limestone.

Diamond (hardest) and talc (softest)

Name the hardest and softest mineral on the Moh's scale.

basalt and gabbro

mafic igneous rocks

Time and necessary elements

Other than space, what two additional factors are significant for a crystal to attain habit?

two; non-90°

Part complete Hornblende has _____ cleavage planes at _____ angles.

ash and cinders

Pyroclastic debris from a volcanic eruption can include _____.

conchoidal fracture

Quartz exhibits __________.

minerals

Regardless of their size, most rocks are made up of __________.

Corundum and quartz

Suppose you found a mineral crystal that looked like topaz. What two minerals could you use in a scratch test to help determine if the mineral is indeed topaz?

Dikes and Sills

Tabular Intrusive Bodies:

streak

The color of a powdered form of a mineral produced by rubbing it across a hard surface.

its crystal form

The external expression of a mineral's orderly internal arrangement of atoms is

magmatic differentiation

The formation of one or more secondary magmas from a single parent magma (crystal settling shown below)

sheet

The micas (biotite and muscovite) exhibit what type of silicate structure?

a halide mineral.

The mineral fluorite is an example of:

condult

The pipelike feature through which magma travels upward from an underground magma chamber

one silicon atom and four oxygen atoms

The silicon-oxygen tetrahedron contains:

mechanical breakage along planes of weakness within the mineral.

The property of cleavage reflects:

how the atoms in silicon-oxygen tetrahedra are shared.

The ratio of silicon to oxygen atoms in silicate minerals depends on:

Mineral Habit

The shape a mineral grows into, given sufficient space.

olivine; mantle

Ultramafic rocks contain __________ and are commonly found in __________.

pyroclastic materials

Volcanoes eject pulverized rock and lava fragments called

amount of gas in the magma

Which parameter has an influence on whether a volcanic eruption will be effusive or violent?

Halite is used for common salt, gypsum is used in plaster, and graphite is used as pencil lead.

What are the economic uses of three common nonsilicate minerals?

Bonds of equal strength in all directions

What causes a lack of cleavage in some minerals?

A small amount of impurities in the crystal structure.

What causes the same mineral to occur in varieties that are different colors?

enclosed spaces

What discourages minerals from achieving habit?

diamond

What is a well-known polymorph of graphite?

ice

What is an example of a mineral?

If a mineral scratches an object, then the mineral is harder than the object.

What is the basic foundation of Moh's hardness scale?

Calcite

What mineral is not scratched by a fingernail, but is scratched by a copper penny?

Feldspars

What minerals make up half of Earth's crust?

decompression melting

When hot, solid mantle rock ascends, it moves to areas of lower pressure. This reduction in pressure allows the hot material to melt into a less compressed liquid phase.

extrusive rock

When lava erupts at Earth's surface, what type of rock is produced?

Oregon

Where is Crater Lake?

water vapor

Which gas is most abundant in basaltic lavas?

Color is the least useful property for identification, as the same mineral type can be found in several different colors due to impurities in the mineral.

Which mineral property is the least useful for identifying minerals, and why?

garnet and biotite

Which of the following is considered a ferromagnesian silicate?

Volcanic rocks are often more resistant to erosion than surrounding rock.

Why are volcanic rocks often exposed at Earth's surface as hills, ridges, and mountains surrounded by areas of lower elevation?

It is less dense than the surrounding rock.

Why does magma have a tendency to rise after its formation?

glass has a disorderly atomic structure

Why is glass is not considered a mineral?

Independent; Mg2+ and Fe2+

__________ SiO4 4- tetrahedra join with __________ ions to produce the mineral olivine in the rock peridotite.

rock-forming; economic minerals

_____________________ minerals consist of a few types of minerals that are abundant in Earth's crust, whereas _______________ are less abundant and are used extensively in the manufacture of products.

silicon-oxygen tetrahedron

a four-sided figure with a silicon atom in the middle bonded to four neighboring oxygen atoms.

Caldera

a large depression that forms following an eruption of a volcano and signifies the subsequent collapse of the volcano and Earth's surface/crust.

basalt plateaus

a large igneous provinces

Minerals

a naturally occurring, inorganic solid that has a crystal structure and a definite chemical composition. Composed of atoms of 2 or more elements.

The East African Rift Valley

a present-day example of a continental rift

surge

a small amount of ash that separates from the main body of the pyroclastic flow

Sill (right)

a tabular, concordant pluton

Dike (left)

a tabular, discordant pluton

Remote sensing devices

aid in monitoring limited-accessibility volcanoes

Hawaiian Islands

an example of modern-day mantle plume volcanism

vent

an opening where volcanic materials erupt at the Earth's surface, and can form on the flanks of a larger volcano in the case of a parasitic cone

quartz

an unidentified mineral that is clear, exhibits conchoidal fracture, and can scratch glass

Cleavage and Fracture

are mineral properties that reflect the internal characteristics of crystalline structure.

mantle plume

ascends towards the surface

Color varieties

associated with trace amounts of chemical impurities; although generally not abundant enough to warrant compositional change, these elements can affect a mineral's color.

unit cells

atomic arrangement that results in the basic building blocks of a mineral crystal smallest number

Bonds

atoms can form several different types of ___________

Calderas

circular, steep-sided depressions with a diameter >1 km

Both muscovite and biotite are micas that have cleavage in one direction and have a shiny luster. However, unlike clear muscovite, biotite is black because it contains iron and magnesium.

compare and contrast muscovite and biotite.

Viscosity

controls the nature of an eruption

volcanic arcs

develop parallel to the associated subduction zone trench

bombs

ejected as hot lava

Lava

erupted magma

Aleutian Islands and Mariana Islands

examples of modern-day island arcs

diamonds and graphite

examples of polymorphs

Galena

exhibits three sets of cleavage at 90° angles

Volcanic ash

fine glassy fragments

crater

formed on the volcano summit by explosive eruptions and is composed of accumulated volcanic debris.

granitic, andesitic, basaltic, ultramafic

four basic compositional groups of igneous rocks, ranging from the highest silica content to the lowest silica content

Igneous rocks

generally form as molten rock (magma/lava) cools and solidifies.

blocks

hardened or cooled lava

Pahoehoe flows

have smooth surfaces and resemble twisted braids of rope

Aa flows

have surfaces of rough jagged blocks

The volcanoes in the Ring of Fire

having violent eruptions, as most of these volcanoes are composite cones which eject andesitic lava.

parasitic cone

is a small cone on the side or base of a volcano that has formed during repeated flank eruptions.

Transparent

light and an image are visible through the sample

Pumice

light gray or pink porous rock from frothy intermediate and felsic lava

Translucent

light, but no image is transmitted

Pyroxene and Olivine

minerals that are typically found in igneous rocks with a low silica content

Plagioclase Feldspar and Quartz

minerals typically found in igneous rocks that have a high silica content

Magma

molten rock that usually contains some crystals and varying amounts of dissolved gases

a silicon-oxygen tetrahedron

most common mineral group

Lahar

mudflow on an active or inactive volcano

Opaque

no light is transmitted

new ocean basin

often forms after continental rifting

Lapilli

pea to walnut sized fragments

specific gravity

ratio of a mineral's weight compared with the weight of an equal volume of water

Scoria

reddish-brown porous rock from frothy mafic lava

magma chamber

results when magma collects or ponds due to its density being higher than that of overlaying materials.

Felsic and intermediate composition magmas

rich in silica and may exist at lower temperatures, causing them to be viscous (thick and sticky)

lava dome

shaped mass composed of rhyolitic lava

geothermal gradient

temperatures in the upper crust increase about 25o C per kilometer

Crystallization

the cooling of magma which results in the formation of minerals

Crater Lake

type calderas: Composite volcanoes

Luster

the quality of light reflected from a mineral's surface

Hawaiian

type calderas: Shield volcanoes

Yellowstone

type calderas: Supervolcanoes

volcanic neck

the remains of magma that solidified in a volcanic conduit

hardness

the resistance of a mineral to being scratched

Cleavage

the splitting of minerals along natural planes of weakness.

non-silicate minerals

they serve as oceanic crust

Viscous magma

traps gas effectively, with gas content being a major driving force behind the style of a volcanic eruption.

False

true or false: All minerals have cleavage.

silicon and oxygen

two most abundant elements in the continental crust

Laccoliths

•Forcibly injected underneath/between sedimentary strata •Causes the overlying strata to arch upward

Batholith

•Largest intrusive body •Surface exposure of 100+ square kilometers