Geology Exam 1
What material was added to powdered rock during Tuttle and Bowen's experiments?
water
Which of the following could cause rock to melt?
- increase in temp - change in composition - decrease in pressure
As revealed in the model, the size (diameter) of Earth's inner core is:
1221 km
Based on information provided for the model and the view from above showing the grid squares, approximately how far from the coast of the Japanese island arc is the deepest portion of the trench nearest to annotation #1?
200-300 km
Viewing the model from the various side angles, what is the approximate depth of the focus of the March 2011 Tōhoku earthquake, represented by the largest sphere along the megathrust surface (the red sphere)?
30 km
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?
5 cm per year
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?
800 pounds
What is required to generate an igneous rock with a fine-grained texture?
A fine-grained texture is the product of rapid cooling and crystallization of lava.
The nebular theory is the most widely accepted view of the origin of our solar system. Which of the following is a short description of the nebular theory?
A large cloud of space gas and dust condensed and contracted to form a rotating disk with a star formed at the center. Repeated collisions caused bodies to coalesce, leading to the current configuration of our solar system.
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?
All of the responses are correct.
The __________ is an example of an old mountain belt, while the Himalayas represent a(n) __________.
Appalachian Mountains; young mountain belt
Which of the following is a layer of the Earth that is classified NOT by composition, but by physical properties?
Asthenosphere
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?
Canadian Shield, Appalachians, North American Cordillera
Which of the following best describes the term cleavage?
Cleavage is the splitting of minerals along natural planes of weakness.
Which of the following statements best describes Wegener's idea of continental drift?
Continents were formerly in different positions on the Earth and have shifted to their present locations over time.
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
Name the hardest and softest mineral on the Moh's scale.
Diamond (hardest) and talc (softest)
Transform boundaries connect segments of mid-ocean ridges.
Divergent boundaries
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.
In general, why does Earth's crust sit on top of the mantle?
Earth's crust is less dense than the mantle.
What is the category name for the largest division of time used on the geologic time scale?
Eon
Color is a reliable identification technique for minerals.
False
How was the fossil record of ancient life used to support Wegener's hypothesis about Pangaea?
Fossils of identical organisms were found on several continents, indicating the continents were once joined.
You have found a mafic rock with a phaneritic texture. What is a potential rock name?
Gabbro
Which of the following exhibits three sets of cleavage at 90° angles?
Galena
Why is glass is not considered a mineral?
Glass has a disorderly atomic structure.
What type of texture occurs in igneous rocks that cool so rapidly that unordered ions are "frozen" in place?
Glassy
How are felsic magmas formed?
Heat from the mantle melts part of the lower crust.
Intrusive and extrusive igneous rocks are classified based on what criteria?
How quickly the molten rock cools and crystallizes, and where this occurs with respect to Earth's surface
Which of the following is a mineral?
Ice
What is the basic foundation of Moh's hardness scale?
If a mineral scratches an object, then the mineral is harder than the object.
Layers are the result of magma flowing into a crack in other rock
Igneous layers
How are igneous rocks formed?
Igneous rocks are formed by the cooling and crystallization of molten rock.
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
All of the following criteria define a mineral except:
It is organic.
Why does magma have a tendency to rise after its formation?
It is less dense than the surrounding rock.
What is one way a glassy texture forms?
Lava cools rapidly.
How is the thickness of the lithosphere going to change as it moves away from a divergent plate boundary?
Lithosphere will thicken as more mantle is added.
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.
________ refers to a mineral's intensity and quality of reflected light.
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 is true about mafic igneous rocks?
Mafic igneous rocks are rich in Fe, Mg, and Ca.
The Jurassic Period lies in the _____ Era, which was dominated by large terrestrial vertebrates, or _____.
Mesozoic; dinosaurs
Layers are the result of alignment of minerals under directional pressure.
Metamorphic layers
How do rocks differ from minerals?
Minerals aggregate to form rocks, but rocks do not aggregate to form minerals.
A scientist creates diamonds using high-pressure laboratory experiments. These diamonds are not considered minerals because which of the following requirements has been violated?
Minerals must occur naturally.
Based on the diagram shown in the video, name two minerals that are unlikely to coexist in the same igneous rock.
Muscovite and pyroxene
Which of the following statements about divergent boundaries is true?
New ocean crust is created at a divergent boundary.
Do fracture zones near transform boundaries play a role in plate motion?
No, fracture zones play no role in plate motion.
Crustal rifting is currently occurring in East Africa. Which of the following features would you expect to find there?
Normal FaultsLong, wide valley Lava flows All of the above are correct
What is the main material being subducted at an ocean-continent convergent boundary
Oceanic lithosphere
Which of the following is not part of the definition of a mineral?
Organic
Which of the following textures describes an igneous rock with anomalously large crystals?
Pegmatitic
Which of the following textures indicates two stages of cooling and crystallization?
Porphyritic
How do mafic volcanic rocks get to Earth's surface?
Pressure from overlying crust forces mantle magmas through cracks to Earth's surface. These magmas erupt out of volcanoes, cool, and solidify into rock.
Based on what you learned in this video, what minerals make up rhyolite?
Quartz, K-feldspar, and plagioclase feldspars, with relatively fewer biotite and amphiboles
Which of the following rock types is most abundant on Earth's land surface?
Sedimentary rocks
Which of the following statements about rock melting is most accurate?
Rock can remain solid, become partially melted, or melt completely at the same depth within Earth, depending on the temperature.
Which fault in Southern California was created by the sliding of the Pacific Plate past the North American Plate?
San Andreas Fault
Layers are the result of deposition of different types and sizes of pa
Sedimentary layers
What evidence supports that the glaciers on the southern continents were once part of a single, massive ice sheet?
Striations
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.
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 Juan de Fuca Plate has right-lateral motion with the Pacific Plate along the transform Mendocino Fault
Why is the geologic time scale more detailed in the Phanerozoic than in previous eons?
The Phanerozoic Eon is more detailed because of the presence of organisms with hard parts and the rapid increase in biodiversity.
Why is water a necessary component of the melting process in subduction zones?
The addition of water lowers the melting temperature of rock.
Which of the following best describes the term streak?
The color of a powdered form of a mineral produced by rubbing it across a hard surface
What are two differences between oceanic crust and continental crust?
The continental crust is thicker and less dense than oceanic crust.
When matching up once-joined continents such as South America and Africa, the coastlines do not fit together as nicely as the continental shelves. Why might this be the case?
The continental shelves are the edges of the continent. The shoreline simply shows where the sea level is in relation to topography.
Why might the Pacific Ocean slab depicted in the model be descending so steeply?
The descending slab is far from its origin at a spreading center and is thus older, denser, and thicker than at other subduction zones.
What does it mean if an igneous rock has an aphanitic texture?
The igneous rock exhibits mineral crystals too small to see with the naked eye.
The enormous cloud of gas and dust initially condensed due to particle attraction. What force then pulled the cloud into a flat disk shape?
The inward pull of gravity.
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?
The oceanic crust The continental crust The upper mantle down to a depth of about 100 km
Using a calendar year as an analogy to the geologic time scale, when do the oldest anatomically modern humans appear on Earth?
The oldest human fossils show up at about eleven minutes to midnight on December 31st.
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 does an igneous rock with a pyroclastic texture tell a geologist?
The rock was likely formed by a violent volcanic eruption.
When moving away from a divergent boundary in either direction, which of the following statements is true?
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.
What object or class of objects makes up most of the solar system's mass?
The sun
Most igneous rocks never reach the surface. However, igneous rocks other than those formed in volcanoes are found exposed on many parts of Earth. How do you account for this phenomenon?
They formed at depth and have been exposed by uplift and erosion.
Why is Tuttle and Bowen's experiment useful to geologists?
This experiment allows geologists to interpret where granitic rock solidifies beneath Earth's surface.
Other than space, what two additional factors are significant for a crystal to attain habit?
Time and necessary elements
What role do transform boundaries play?
Transform boundaries connect other segments of plate boundaries.
What is the relationship between transform boundaries and mid-ocean ridges?
Transform boundaries connect segments of mid-ocean ridges.
Which type of tectonic boundary is the result of two tectonic plates sliding past each other?
Transform boundary
Divergent boundaries are not one, smooth ridge of separation. Instead, they are broken into a series of segments, with different segments of fault offset from others. What features allow for the offset of divergent boundaries?
Transform faultsReverse faults
Refer to the periodic table of the elements to help you answer this question. 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
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
Late Paleozoic sedimentary rocks often contain extensive coal seams that were used to support the existence of Pangaea. What would the climate have been at that time and at the location where the coal deposits were formed, and what would it indicate about the continent's past latitude?
Warm, humid climate near the Equator
Where does the water involved in melting at subduction zones come from?
Water contained within minerals in the subducting plate is released during metamorphism.
How does water content of granitic magmas change as the magmas move towards Earth's surface?
Water content decreases.
How does water content of melt change with increasing pressure?
Water content increases with increasing pressure
Name the epoch, period, era and eon in which we currently live.
We live in the Holocene Epoch of the Quaternary Period, which is part of the Cenozoic Era and Phanerozoic Eon.
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 t
a convergent plate boundary
In general, when will melted rock in the mantle rise?
almost always
Pyroclastic debris from a volcanic eruption can include _____.
ash and cinders
Minerals must be solid, have an orderly atomic structure, have a recognized chemical composition, be naturally occurring, and __________.
be generally inorganic in origin
Most marine organisms produce the mineral substance ________, which will later become limestone.
calcite (CaCO3)
Quartz exhibits __________.
conchoidal fracture
Which two processes commonly generate magma?
decompression melting and wet melting (the addition of volatiles)
What discourages minerals from achieving habit?
enclosed spaces
When lava erupts at Earth's surface, what type of rock is produced?
extrusive
Which of the choices below lists the four basic compositional groups of igneous rocks in order from highest silica content to lowest silica content?
felsic, intermediate, mafic, ultramafic
Through the course of time, bodies in our solar system have become __________ and __________ due to collisions.
fewer in number; larger in size
Igneous rocks of felsic composition have __________ and __________ relative to mafic igneous rocks.
greater silica; lower melting temperature
A phaneritic texture is characteristic of a(n) __________ igneous rock that cooled __________.
intrusive; below the surface
The external expression of a mineral's orderly internal arrangement of atoms is referred to as:
its crystal form.
The amount or quality of light that is reflected from a mineral surface is known as __________.
luster
The property of cleavage reflects:
mechanical breakage along planes of weakness within the mineral.
Regardless of their size, most rocks are made up of __________.
minerals
Oceanic lithosphere contains oceanic crust and the __________.
outermost part of mantle beneath the oceanic crust
Which of the following substances is a mineral?
quartz
In the field, you find an unidentified mineral that is clear, exhibits conchoidal fracture, and can scratch glass. This mineral is most likely:
quartz.
The principal mineral used in making glass is:
quartz.
Hardness describes a mineral's __________.
resistance to being scratched
Transform boundaries are classified under which type of fault?
strike-slip
What experiments did Tuttle and Bowen perform?
tests of the temperature and pressure conditions required to melt granite and form magma
Which of the following lithospheric plates is not included among the seven largest?
the Philippine plate
Crystal habit is the shape that a mineral develops by the repetition of __________.
the basic unit cell of a mineral
As a result of partial melting, magma originates in __________.
the mantle and crust
Earth's lithospheric plates are composed of crust and which of the following layers?
the outermost portion of the mantle
What is peridotite?
the rock making up the mantle
Hornblende has _____ cleavage planes at _____ angles.
two; non-90°
When will magma rise to Earth's surface?
when the magma is less dense than adjacent rock
