GEO 111 Exam 1

A __________ is another term for a basin formed by crustal extension

Graben

An igneous rock that contains quartz and potassium feldspar would have a mineralogic content placing it in the range of __________.

Granitic or felsic rocks

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

How the atoms in silicon-oxygen tetrahedra are shared.

Iceland is unique along the Mid-Atlantic Ridge because it is the only part of the ridge that is elevated above sea level. Why might this be the case?

Iceland is receiving magma from a mantle plume and receiving magma from decompression melting along the Mid-Atlantic Ridge.

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

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

The oceanic crust is roughly 7 km (4.5 mi) thick and the continental crust's thickness averages about 35 km (22 mi). The deepest drilling into Earth's interior was the Kola Superdeep Borehole on the Kola peninsula of continental Russia, reaching 12.3 km (40,230 ft). Where within the model of Earth's interior would that depth fall?

In approximately the upper third of the continental crust

___________ is igneous activity that occurs __________ plate margins.

Intraplate volcanism; away from

How is information about magnetic fields recorded in rocks?

Iron particles in magnetically susceptible minerals within basaltic lava align with the magnetic field of the Earth while the lava is still liquid and then freeze in position when the lava solidifies.

All of the following criteria define a mineral except: It is inorganic. It is naturally occurring. It is organic. It has an orderly internal structure. It has a well-defined chemical composition. Submit

It is organic.

The external expression of a mineral's orderly internal arrangement of atoms is referred to as:

Its crystal form.

What is one way a glassy texture forms?

Lava cools rapidly.

What do you think will happen to the location of Los Angeles with continued activity along the San Andreas Fault over a long time span?

Los Angeles will slide to the northwest.

The amount or quality of light that is reflected from a mineral surface is known as __________.

Luster

Since color is not a very useful way to identify a mineral, what other optical property or properties can be used?

Luster and streak

Which of the following scenarios best describes the activity present along the Mid-Atlantic Ridge?: Segments of seafloor slide past each other without creating or destroying crustal material. Magma is created by partial melting of crustal material as it sinks. Old seafloor is consumed as it is forced beneath another segment of seafloor. A plume of hot mantle material is pushing up against the crust, adding material to the crust to thicken it. Magma wells up at the center of the ridge, which pushes the old seafloor apart as new seafloor is created.

Magma wells up at the center of the ridge, which pushes the old seafloor apart as new seafloor is created. Submit

The property of cleavage reflects:

Mechanical breakage along planes of weakness within the mineral.

Some of Iceland's volcanoes are covered by large glaciers. What are some of the hazards that may occur if one of those glacier-covered volcanoes erupted?

Meltwater can result in massive jökulhlaups and Pillow basalts will form.

Hardness describes a mineral's __________.

Resistance to being scratched

What is a fine-grained igneous rock composed primarily of very small crystals of potassium feldspar and a few large crystals of quartz?

Rhyolite Porphyry

Which of the following textures indicates two stages of cooling and crystallization? Porphyritic Phaneritic Glassy Frothy Pyroclastic

Porphyritic

Basalt is an igneous rock that can be identified by its small crystals. What are they composed of?

Pyroxene and calcium-rich plagioclase feldspar

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

Quartz

The principal mineral used in making glass is:

Quartz

Which of the following substances is a mineral?: pearl quartz granite amber petroleum

Quartz

What features of the model indicate that basalt erupts as a fluid, low-viscosity-flowing material rather than as sticky or blocky masses?

Ropey, folded surface structures.

Which fault in Southern California was created by the sliding of the Pacific Plate past the North American Plate?

San Andreas Fault

In the field, you find an unidentified mineral that is clear, exhibits conchoidal fracture, and can scratch glass. This mineral is most likely: muscovite gypsum calcite quartz hornblende.

Quartz.

How were scientists able to determine the date of the magnetic reversals during seafloor spreading?

Small marine fossils in deep-sea sediments give the age of the portions of the seafloor.

Why is decompression melting common at mid-ocean ridges but not at subduction zones?

Tectonic plates are moving apart at mid-ocean ridges, resulting in a lowering of pressure beneath the ridge. Tectonic plates are moving together at subduction zones, resulting in an increase of pressure under new mountains.

At a divergent boundary, what is the relative motion of the plates on each side of the boundary?

The plates move away from each other.

What is peridotite?

The rock making up the mantle

What does an igneous rock with a pyroclastic texture tell a geologist?

The rock was likely formed by a violent volcanic eruption.

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?

Corundum and quartz

Select what is true or false for each statement: #1. Rift-flanking mountains and the adjacent basin are both shown in the photo #2. The basin was uplifted relative to the mountains. #3. A normal fault must be present between the mountains and the basin. #4. A reverse fault must be present between the mountains and the basin

#1 True #2 False #3 True #4 False

As revealed in the model, the size (diameter) of Earth's inner core is:

1221 km

Which of the following best describes the difference between granite and rhyolite? 1. Both of these rocks show a difference in composition. 2. Granite is phaneritic and rhyolite is aphanitic. 3. Granite is light in color relative to rhyolite. 4. Granite is formed from cooled lava, while rhyolite is formed from cooled magma. 5. Granite contains higher amounts of amphibole relative to rhyolite.

2. Granite is phaneritic and rhyolite is aphanitic.

As revealed in the model, the size (diameter) of Earth's core is:

3471 km

Movement of plates away from each other at divergent boundaries typically shows which of the following average velocities?: 50 km per year 5 m per year 50 cm per year 5 cm per year 5 km per year Submit

5 cm per year

Using the figure, when was the last time the Earth had a magnetic reversal?

700,000 years ago Submit

Gold has a specific gravity of almost 20. A 5-gallon bucket of water weighs 40 pounds. How much would a 5-gallon bucket of gold weigh? (20x40)

800 pounds

Currently the Juan de Fuca plate is interacting with the North American plate where inland volcanoes and deep focus earthquakes are occurring. What type of plate boundary is this?

A convergent plate boundary

The mineral fluorite is an example of:

A halide mineral.

What is an accessory mineral?

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

What is the D" layer?

A partially molten layer above the outer core at the base of the mantle. Submit

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

A small amount of impurities in the crystal structure.

What main characteristics are used to distinguish the two types of mountain belts?

Age and degree of erosion

Which of the following processes can be observed at the margins of lithospheric plates?: faulting earthquakes volcanoes mountain building

All of the responses are correct. Submit

What is the rock name of an intermediate rock with two distinct grain sizes?

Andesite porphyry.

The __________ is an example of an old mountain belt, while the Himalayas represent a(n) __________.

Appalachian Mountains; young mountain belt

Decompression melting occurs when the _________________ upwells

Asthenosphere

Structures such as columnar joints are found near Gullfoss in the Reykjanes Peninsula. How were these structures created?

Cooling lava contracts, creating fractures.

What causes a lack of cleavage in some minerals?

Bonds of equal strength in all directions

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

Calcite

Which of the following correctly states the order in which major features of North America were formed?: Stable platform, Canadian Shield, Appalachians Appalachians, stable platform, Canadian Shield Canadian Shield, Appalachians, North American Cordillera Appalachians, Greenland Shield, Canadian Shield Canadian Shield, North American Cordillera, Appalachians

Canadian Shield, Appalachians, North American Cordillera

The layers of Earth are based on what two sets of characteristics?

Chemical composition and physical properties

Which of the following best describes the term cleavage?: Cleavage is the colored mark that a mineral makes when scratched on a porcelain tile. Cleavage is the characteristic growth pattern or shape of a mineral. Cleavage describes the quality and amount of light reflected from a mineral surface. Cleavage describes a mineral's resistance to abrasion. Cleavage is the splitting of minerals along natural planes of weakness.

Cleavage is the splitting of minerals along natural planes of weakness.

What is the classification of igneous rocks based on?

Composition and texture

Which part of the Earth is responsible for generating the planet's magnetic field?

Core

Which two processes commonly generate magma?

Decompression melting and wet melting (the addition of volatiles)

Which of the following could cause rock to melt? decrease in pressure increase in pressure increase in temperature decrease in temperature change in composition

Decrease in pressure, increase in temperature, and a change in composition.

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

Diamond (hardest) and talc (softest)

What is a coarse-grained rock composed of intermediate plagioclase feldspar and pyroxene?

Diorite

In studies of rock obtained from ocean basins all over Earth, the oldest ages obtained are approximately 200 million years before the present. Why have no older oceanic rocks been discovered?

Due to tectonic activity, rocks on the ocean floor are continually recycled.

What discourages minerals from achieving habit?

Enclosed spaces Submit

Continental rifts are formed by ____________ forces.

Extensional

Once a source rock partially melts, what does it produce?

Felsic magma and mafic residue Submit

Which of the following exhibits three sets of cleavage at 90° angles?: Feldspar Mica Galena Calcite Fluorite

Galena

Which of the following statements about divergent boundaries is true?: Lithospheric plates move closer to each other at divergent boundaries. New ocean crust is created at a divergent boundary. Mountains are created at divergent boundaries. New continental crust is created at divergent boundaries. Ocean crust is consumed at a divergent boundary.

New ocean crust is created at a divergent boundary.

Are there any features observed on this model that indicates this sample is a pyroclastic rock?

No, there are no features visible on this model that would indicate this rock is pyroclastic.

A _________________ separates the basin from the adjacent uplifted mountains

Normal fault

What are the two types of crust?

Oceanic and continental

Ultramafic rocks contain __________ and are commonly found in __________.

Olivine; mantle

The silicon-oxygen tetrahedron contains:

One silicon atom and four oxygen atoms.

Which of the following textures describes an igneous rock with anomalously large crystals?

Pegmatitic

The western edge of the Juan de Fuca Plate is a divergent boundary with a ragged, zigzag edge. (See the figure.) Which of the following describes the motion of the Juan de Fuca plate on its southern boundary at the Mendocino Fault?: The Mendocino Fault prevents the Juan de Fuca Plate from moving. The Juan de Fuca Plate has right-lateral motion with the Pacific Plate along the transform Mendocino Fault. The Mendocino Fault pushes the Juan de Fuca Plate, forcing to slide westward. The Mendocino Fault subducts the new seafloor. The Mendocino Fault is a divergent boundary, which pushes the Juan de Fuca Plate northward

The Juan de Fuca Plate has a right-lateral motion with the Pacific Plate along the transform Mendocino Fault.

Which of the following lithospheric plates is not included among the seven largest?: the Antarctic plate the Philippine plate the African plate the South American plate the Australian-Indian plate

The Philippine plate

Why is water a necessary component of the melting process in subduction zones?

The addition of water lowers the melting temperature of rock.

The upper mantle can be divided into the asthenosphere and lithosphere based on what physical properties?

The asthenosphere is solid, but mobile, while the lithosphere is solid and relatively rigid.

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

The basic unit cell of a mineral

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

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

Which of the following best describes the term streak?: When both light and an image are visible through a mineral sample. The amount or quality of light reflected from a mineral surface. When no light is transmitted through a mineral sample. The color of a powdered form of a mineral produced by rubbing it across a hard surface. The arrangement of atoms in an orderly, repetitive structure.

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

As labeled in the model's close-up cut-out, which shows the details of the upper mantle and the types of crust, the lithosphere includes which of the following? (Select all that apply.): The oceanic crust The asthenosphere The upper mantle down to a depth of about 100 km The continental crust The upper mantle down to a depth of about 660 km Submit

The oceanic crust The upper mantle down to a depth of about 100 km The continental crust

When moving away from a divergent boundary in either direction, which of the following statements is true?: The rocks become more felsic in composition. Oceanic crustal rocks are being consumed at the divergent plate boundary. The rocks are rapidly converted to sediments. The rocks increase in age. The rocks decrease in age.

The rocks increase in age.

If stable platforms represent sedimentary rocks that cover continental shields, then what statement must be true?

The sedimentary rock atop the stable platforms must be younger than continental shields.

Which of the following best describes mineral habit?

The shape a mineral grows into, given sufficient space.

The Mid-Atlantic Ridge crosses through Iceland. Physical features such as tensional fractures and cinder cone volcanoes are all aligned NE-SW. What does this indicate about the directions the tectonic plates are moving?

The tectonic plates are separating to the NW and SE.

What do pumice and scoria have in common?

They both exhibit a vesicular texture.

During extension the lithosphere ___________

Thins

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

Time and necessary elements

Which type of tectonic boundary is the result of two tectonic plates sliding past each other?

Transform boundary

If the number of protons in an electrically neutral atom is 92 and its mass number is 238, what is the name of that element, its number of electrons, and number of neutrons?

Uranium, 92 electrons, and 146 neutrons Submit

Which statement accurately describes continental shields?

Very old, stable regions composed of igneous and metamorphic rocks

Which of the following describes a texture containing bubble-shaped cavities?

Vesicular

Where does the water involved in melting at subduction zones come from?

Water contained within minerals in the subducting plate is released during metamorphism.

What feature on this model can be used to reveal the rock's mafic composition?

Yellowish stains on the surface.

The rocks that make up Iceland have a very specific age pattern related to the presence of the Mid-Atlantic Ridge. What is this age progression?

Youngest rocks near the center of Iceland, oldest rocks near the East and West Shores

If all were accessible, which of the following items would be best for geologists to examine to better understand Earth's internal structure?

an iron meteorite

Quartz exhibits __________.

conchoidal fracture

Earth's lithospheric plates are composed of crust and which of the following layers?: the outermost portion of the mantle the middle portion of the mantle the core the innermost portion of the mantle the outermost portion of the core

the outermost portion of the mantle

Hornblende has _____ cleavage planes at _____ angles.

two; non-90°