Exam 1

Which of the following are true of felsic magmas?

ALL OF THE ABOVE - High gas pressures commonly lead to highly explosive eruptions / They do not allow gas bubbles to escape easily / They tend to have high viscosities

Which of the following is true about rocks and minerals?

ALL OF THE ABOVE - a single rock can include more than one mineral, e.g. quartz and feldspar / a rock can be composed of only one mineral, e.g. entirely of quartz grains / a mineral is composed of chemical elements

Which of the following are dangerous aspects of composite volcanoes?

ALL OF THE ABOVE - landslides and mudflows / an eruption column / pyroclastic flows

Important characteristics to observe in rocks include:

ALL OF THE ABOVE - types of minerals present / sizes and shapes of crystals / presence or absence of layers

The following criteria define a mineral. Choose the two of these that control the physical properties and chemical reactivity of minerals?

Crystalline structure AND Definite chemical composition

A phaneritic texture (coarse-grained) intrusive igneous rock composed mostly of feldspar and quartz is called:

Granite

If you were to melt a piece of granite, the first mineral to melt would be _____.

Quartz

If you were to slowly cool a felsic melt, the last mineral to crystallize would be _____.

Quartz

How is magma created in a subduction zone?

Subduction brings one plate to a depth hot enough for minerals to release water; this water causes melting in the overlying asthenosphere.

Igneous rocks are classified primarily on _______ and ________ (choose two).

Texture AND Composition

11) What happens to a mountain in terms of isostatic adjustment following a period of significant erosion?

The continent underneath will be uplifted.

Minerals have a crystal structure. What does this mean?

Atoms in a mineral are arranged in an ordered, and infinitely repeating geometric pattern.

Which of the following statements correctly states how early crystallization affects the composition of a magma?

BOTH Early crystallization causes the MgO (mafic) content to decline in the magma. AND Early crystallization causes the SiO2 content to increase in the magma.

If a mineral lacks planes along which it may cleave, what will occur?

The mineral will fracture in an irregular pattern

Which of the following minerals is typically green and has no cleavage?

olivine

A lava solidifies into nonvesicular basalt instead of vesicular basalt because:

the magma has a low content of gas

The main reason why the hypothesis of continental drift was not widely accepted was:

There was no mechanism to move continents through the oceanic crust

Which of the following are ways that viscosity affects gases in magma?

Viscous magma prevents gas from escaping easily.

Which of the following factors indicates a high risk for volcanic mudflows or lahars?

a volcano with a thick covering of snow or ice

At what depth do gas bubbles have the most effect on magma?

at very shallow levels, such as within the volcano

If bubbles cannot escape easily from a magma, the resulting eruption is likely to:

be explosive

How fast do plates move relative to one another?

centimeters per year

Which of the following igneous rocks would be formed by the slowest cooling?

coarse granite

Which mineral property is the least reliable for identifying a mineral?

color

The most dangerous type of volcano is a:

composite volcano

Which layer in the Earth has a composition similar to granite, which is an igneous rock composed mainly of quartz, K-feldspar and Na-rich plagioclase feldspar?

continental crust

Which layer in the earth is similar to the chemical composition of granite?

continental crust

Which layer in the Earth has a composition similar to an iron-nickel meteorite?

core

In which of the following types of bonding do atoms share one or more electrons, as shown in this figure?

covalent

The main layers of the Earth in correct order, from the surface moving down, are:

crust, mantle, outer core, inner core

As two oceanic plates diverge at mid-ocean ridges, melting of the rising mantle occurs due to:

decompression

The vast majority of new oceanic crust is created is by:

eruption of lavas and solidification of magmas at depth

Which of the following causes magma to be less viscous?

fewer silicate chains in the magma

Volcanoes and earthquakes:

have many areas of overlap in their distributions on Earth

Which one of the following IS a mineral?

ice

Rock that has formed from cooling magma or lava is:

igneous rock

An igneous rock that solidifies below the surface is called a(n):

intrusive rock

In which of the following types of bonding do atoms loan one or more electrons, as shown in this figure?

ionic

The three elements most abundant in the entire Earth are:

iron, oxygen, silicon

Which of the following igneous rocks has a texture consistent with a magma that cooled and solidified slowly at first, followed by more rapid cooling, i.e. a two-stage cooling?

large, early formed crystals surrounded by smaller, late formed crystals

When fluid lava (low viscosity) erupts onto the surface, it typically produces:

lava flows

Which of the following minerals would likely crystallize early from magma?

mafic minerals

Which layer in the earth is similar in chemical composition to the green mineral olivine?

mantle

A divergent plate boundary is most likely associated with a(n):

mid-ocean ridge

Enormous mountain belts and high plateaus can be formed when two continental plates collide and:

neither is subducted

Which layer in the earth is similar in chemical composition to basalt, a dark lava rock?

oceanic crust

Which of the following Earth layers is the thinnest?

oceanic crust

What occurs at mid-ocean ridges?

oceanic crust is created

What occurs at subduction zones?

oceanic crust is destroyed

The mineral halite grows as cube-shaped crystals because:

of the arrangement of atoms in the crystal lattice

13) Lava is molten rock that cools:

on the surface

What type of cleavage is illustrated in this figure?

one direction

Which mineral is commonly pinkish and has two perpendicular directions of cleavage?

potassium feldspar

A mineral is light colored, transparent, has a hardness of seven, and fractures rather than cleaves. Which mineral is it?

quartz

This volcano is broad and low, and is composed of basaltic lava flows. What kind of volcano is it?

shield volcano

Which of the following terms refers to the compound SiO ₂?

silica

The most important class of rock-forming minerals on Earth is:

silicates

What type of atom is represented by the small sphere in the center of this silica tetrahedron?

silicon

The two elements most abundant in the Earth's crust are:

silicon and oxygen

The process of one tectonic plate sliding beneath another tectonic plate is called:

subduction

Which one of the following is NOT a mineral?

synthetic glass

What arrangement of atoms does this diagram illustrate?

tetrahedron

Mid-ocean ridges are higher than surrounding oceanic crust primarily because:

the lithosphere is thinner and hotter

The higher the gas pressure builds in a magma:

the more explosive an eruptions it is likely to produce

The principle of isostasy refers to

the relationship between regional elevations and thickness of crust

An igneous rock that solidifies on Earth's surface is called a(n):

the rock broke apart as it flowed

A finely crystalline or glassy igneous texture indicates that:

the rock cooled quickly

Coarsely crystalline igneous textures indicate that:

the rock cooled slowly

A porphyritic igneous texture indicates that:

the rock cooled slowly and then quickly

What is the underlying geologic explanation for why western South America is so different from eastern South America?

the western side is a plate boundary and the eastern side is not

As depth increases into the Earth,:

there is an increase in temperature and pressure

A vesicular igneous texture indicates that:

there was a lot of gas in the magma

Which of the following combinations would result in the highest regional elevations?

thick, less dense crust

Which of the following is NOT a main type of silicate structure?

triple chains

The Tibetan and Himalaya Plateaus are the result of:

two continental plates colliding producing overthickened crust

What type of cleavage is illustrated in this figure?

two nonperpendicular directions