exam 1 study quizzes & lecture questions
When writing an email, what should I pay attention to? - Write a clear email with a precise question or comment that can be easily understood. - If you haven't received a response after two workdays, resend the email. - Start the subject line with "GEO-101" (without the quotation marks). - All of the above
- All of the above
At what time are the reading quizzes due? - At noon on the dates indicated in the syllabus. - At 8 am on the dates indicated in the syllabus. - At 10 am on the dates indicated in the syllabus. - At midnight on the dates indicated in the syllabus.
- At noon on the dates indicated in the syllabus.
Where do the office hours take place? - In the classroom - At the Ferg - Either in Dr. Plattner's office, Bevill Energy Building, Room 2023, or via Zoom (email Dr. Plattner for the Zoom link).
- Either in Dr. Plattner's office, Bevill Energy Building, Room 2023, or via Zoom (email Dr. Plattner for the Zoom link).
When joining the lecture via Zoom, - I can use any funny name I like - I must use my name the way it appears on Blackboard, otherwise I may not get the extra credit for joining. Also, I need to make sure I am logged in on Zoom using my UA account.
- I must use my name the way it appears on Blackboard, otherwise I may not get the extra credit for joining. Also, I need to make sure I am logged in on Zoom using my UA account.
What type of notes shall I take in class? - I should write down the gist of additional information and context Plattner gives, but which is not already on the slides (as all the slides are on Blackboard). I use the slide number for reference. - I must write down everything that is on the slides. - Notes are not necessary, I will remember everything I hear and see.
- I should write down the gist of additional information and context Plattner gives, but which is not already on the slides (as all the slides are on Blackboard). I use the slide number for reference.
When I submit my SOI, can I drop the final exam? - No, because other faculty teaching GEO101 have decided that this is not permissible, as the final is comprehensive. - No, because Plattner is mean.
- No, because other faculty teaching GEO101 have decided that this is not permissible, as the final is comprehensive.
I missed a reading quiz. Can I make it up at a later time? - Yes, reading quiz deadlines are flexible - No, except under extenuating circumstances. Since the reading quizzes can be taken any time before the deadline, the circumstances need to have been hindering you from taking the quiz for several weeks.
- No, except under extenuating circumstances. Since the reading quizzes can be taken any time before the deadline, the circumstances need to have been hindering you from taking the quiz for several weeks.
I tried to join the class on Zoom but could not get online. Will I now not get participation extra credit? - Yes, that's fine. - No, this would be considered academic misconduct and reported to the dean's office. If your friend has a valid excuse (sickness, work related issues, any university-sanctioned activities, etc), then your friend should email Dr. Plattner for an attendance exemption.
- No, this would be considered academic misconduct and reported to the dean's office. If your friend has a valid excuse (sickness, work related issues, any university-sanctioned activities, etc), then your friend should email Dr. Plattner for an attendance exemption.
I missed a reading quiz deadline. Will this ruin my grade? - Yes, an A will be impossible because of this. - No. If you submit the student opinion of instruction at the end of the semester and upload confirmation on Blackboard, then your two lowest quiz scores and your lowest midterm exam grade will be dropped.
- No. If you submit the student opinion of instruction at the end of the semester and upload confirmation on Blackboard, then your two lowest quiz scores and your lowest midterm exam grade will be dropped.
Do you have to buy the textbook "Essentials of Geology" for the lecture? - Yes, Dr. Plattner checks if each of us has the book and gives us a bad grade if we don't have it. - Not necessarily for the lecture, but may be for the lab (ask your Lab instructor). The reading quizzes for the lecture are based on the book, but you can also look the information up online, or do the reading in the library, or get an older edition, or use the free alternative texbook (link is on Blackboard). - No, the book is not related to the course. - I don't know. Let me quickly email Plattner.
- Not necessarily for the lecture, but may be for the lab (ask your Lab instructor). The reading quizzes for the lecture are based on the book, but you can also look the information up online, or do the reading in the library, or get an older edition, or use the free alternative texbook (link is on Blackboard).
When is the final exam? - On the last day of class - In the week before final-exam-week. - On Wednesday, April 28, 8:00 am - 10:30 am (you can choose online or in the lecture hall).
- On Wednesday, April 28, 8:00 am - 10:30 am (you can choose online or in the lecture hall).
I missed an exam, but have no valid medical excuse. My friends told me that they have often been able to get a makeup exam by submitting a forged medical excuse. Shall I do the same? - Of course. Everyone does it. It's not a big deal. - This is a bad idea as it is considered an academic misconduct. All medical excuses are automatically forwarded to the geosciences front office and checked for validity. If they are deemed forgeries, they are automatically forwarded to the dean's office.
- This is a bad idea as it is considered an academic misconduct. All medical excuses are automatically forwarded to the geosciences front office and checked for validity. If they are deemed forgeries, they are automatically forwarded to the dean's office.
When are Dr. Plattner's office hours? - Mon, Wed, Fri at noon - Thu at 3:40 pm or by appointment. - Tue, Thu at 2 pm - On weekends
- Thu at 3:40 pm or by appointment.
Are there any extra credit opportunities? - Yes. Your attendance counts for up to 5 points extra credit. If you attend x% of the time, you will get x% of the 5 points (x%*5). - No, because Plattner is mean.
- Yes. Your attendance counts for up to 5 points extra credit. If you attend x% of the time, you will get x% of the 5 points (x%*5).
Why is Arrokoth not round? A) Because it is not large enough B) Because it has no magnetic field C) Because it formed much later than the Earth
A) Because it is not large enough
Which of the following statements is correct A) The asthenosphere is part of the mantle B) The mantle is part of the asthenosphere C) Mantle and asthenosphere do not overlap
A) The asthenosphere is part of the mantle
Is salt a mineral? A) Yes B) No
A) Yes
New lithosphere gets created A) at divergent plate boundaries B) at convergent plate boundaries C) at transform plate boundaries D) Answers A and B E) Answers A, B, and C
A) at divergent plate boundaries
Felsic means A) high silica content B) intermediate silica content C) low silica content
A) high silica content
A volcano with magma with a high silica content erupts _________ explosively than volcanoes with low silica content A) more B) less C) as
A) more
Why are not all crystals perfectly shaped (euhedral)? A) Because only lab-grown crystals have a symmetric shape B) Because an obstacle may be in the way during growth C) Crystals usually don't have any symmetry
B) Because an obstacle may be in the way during growth
In which direction did the Pacific plate move with respect to the asthenosphere? A) Mostly to the East B) Mostly to the West C) Mostly to the South
B) Mostly to the West
Is rock candy a mineral? A) Yes B) No
B) No
Which of the following statements is correct? A) The lithosphere is part of the crust B) The crust is part of the lithosphere C) Lithosphere and crust do not overlap
B) The crust is part of the lithosphere
Partial melting leads to ______ silica content in the melt than in the original rock? A) a lower B) a higher C) the same
B) a higher
Flux melting works ... A) by increasing the temperature B) by lowering the melting point C) by reducing the pressure D) all of the above
B) by lowering the melting point
What is the difference between Wegener's "continental drift" and Hess' "seafloor spreading"? A) Both are the same B) "Seafloor spreading" contradicted "continental drift" C) "Seafloor spreading" showed a mechanism for continental drift
C) "Seafloor spreading" showed a mechanism for continental drift
What is the difference between Gabbro and Basalt? A) Gabbro has smaller crystals B) They are chemically different C) Basalt has smaller crystals D) all of the above
C) Basalt has smaller crystals
Why does the sea floor have stripes of different magnetic direction? A) Because new crust formed, cooled, and recorded the field direction B) Because Earth's magnetic field regularly switched North and South pole C) Because of a combination of A and B
C) Because of a combination of A and B
Why are journals interested in publishing new/controversial ideas? A) Because controversial ideas are always true B) Journals never publish new/controversial ideas C) Because their income depends on high- profile publications. New / controversial can be high-profile.
C) Because their income depends on high- profile publications. New / controversial can be high-profile.
Why will peer-reviewers critically examine scientist's work? A) Because scientists all hate each other B) Because the journals pay them well C) Because there is competition for publishing. More publications means better chances for jobs / promotion / funding
C) Because there is competition for publishing. More publications means better chances for jobs / promotion / funding
Why are Oceans on top of the Crust and Mantle? A) Because water is liquid B) Because water is more dense than rocks C) Because water is less dense than rocks
C) Because water is less dense than rocks
How are minerals identified? A) Mostly by looking at their color B) By guessing C) By running through a series of tests including looking at their streak, their hardness, and their cleavage
C) By running through a series of tests including looking at their streak, their hardness, and their cleavage
How does the subducting lithosphere melt the mantle? A) By heating up the mantle B) By reducing the pressure C) By supplying water. Water reduces the melting temperature of the mantle
C) By supplying water. Water reduces the melting temperature of the mantle
From a single location, the direction to the north pole changed. What could this mean A) The north pole moved B) The location moved C) Either A or B, can't tell from one location
C) Either A or B, can't tell from one location
What is the difference between crystal habit and cleavage? A) Cleavage is the shape of the crystal habit is how it breaks B) They are the same C) Habit is the shape of the crystal, cleavage is how it breaks.
C) Habit is the shape of the crystal, cleavage is how it breaks.
Why were Wegener's ideas not accepted by most Scientists A) Language barrier B) Not enough evidence C) No mechanism was known for moving the continents
C) No mechanism was known for moving the continents
Is Death Valley a divergent plate boundary? A) Yes, new crust is created B) No, it is a convergent plate boundary C) Not yet but it may become a plate boundary in the future
C) Not yet but it may become a plate boundary in the future
What happens at the San Andreas Fault? A) California is getting split apart B) California is getting squeezed together C) Plates are grinding past each other
C) Plates are grinding past each other
Why do we have seasons? A) because the Earth moves further away from the sun in winter B) because the Sun gets hotter in winter C) because Earth's rotation axis is tilted
C) because Earth's rotation axis is tilted
Which of the following melts has the lowest silica content? A) felsic B) intermediate C) mafic
C) mafic
The mantle is ____ and it is ____ than the crust A) liquid, denser B) liquid, less dense C) solid, denser D) solid, less dense
C) solid, denser
At a continent-continent collision, which plate subducts? A) The one to the north B) The older one C) The younger one D) None of them
D) None of them
Where do Earthquakes typically occur A) At divergent plate boundaries B) At convergent plate boundaries C) At transform boundaries D) Answers A and B E) Answers A, B, and C
E) Answers A, B, and C
Which of the following statements accurately describes a property that is NOT useful in identifying quartz? a. Color, because quartz can be many different colors. b. Fracture, because quartz does not have fracture. c. Hardness, because quartz is softer than most minerals in Mohs scale. d. Crystal habit, because quartz has a fibrous crystal habit.
a. Color, because quartz can be many different colors.
A black, fine-grained tabular intrusion between two layers of horizontal sedimentary rock must logically be a a. basaltic sill. b. granitic sill. c. basaltic dike. d. granitic dike.
a. basaltic sill.
Intrusive igneous rocks a. cool slowly and are coarse-grained. b. are fine-grained because they cooled slowly. c. are never seen by humans because they form deep in the Earth and are never exposed at the surface. d. are rocks like basalt, andesite, and rhyolite.
a. cool slowly and are coarse-grained.
Earth's magnetic field is created by: a. flow of liquid iron in Earths molten outer core. b. centrifugal force pushing on Earths crust. c. convecting iron-rich silicates in Earths mantle. d. the rotation of the planet on its axis.
a. flow of liquid iron in Earths molten outer core.
Choose the FALSE statement. The paleomagnetic record: a. is a puzzle; it contradicts the sea-floor spreading concept. b. is preserved in basalt layers on land. c. is symmetrical across the mid-ocean ridge. d. is preserved in strips of rock parallel to the mid-ocean ridge.
a. is a puzzle; it contradicts the sea-floor spreading concept.
The rate of sea-floor spreading: a. is fast enough to account for the formation and destruction of oceans many times in Earth's history. b. depends on the type of plate boundary (i.e., convergent, transform) at which it occurs. c. is faster along the Mid-Atlantic Ridge than along the East Pacific Rise. d. has remained constant throughout Earth's history.
a. is fast enough to account for the formation and destruction of oceans many times in Earth's history.
A negative magnetic anomaly: a. is indicated when a magnetometer measures intervals of magnetism that are weaker than expected. b. occurs when Earths magnetic field measured in ancient rocks is the same as today. c. is created when weak magnetic forces in basalt grains add to the force produced by Earths dipole. d. describes the sawtooth pattern of magnetic signal strength measured along the Atlantic Ocean sea floor.
a. is indicated when a magnetometer measures intervals of magnetism that are weaker than expected.
Which of the following is NOT a mineral? a. oil, because it's a liquid, not a solid b. salt, because it's not crystalline c. a gold nugget, because it's a native metal d. pyrite, because it's a chemical compound
a. oil, because it's a liquid, not a solid
An unknown mineral scratches glass, has only average specific gravity, and shows no cleavage but does show conchoidal fracture. Which of the following could it be? a. quartz b. talc c. halite d. mica
a. quartz
When you scrape a mineral along a ceramic plate to observe the color of its powder, you are checking the physical property known as: a. streak. b. luster. c. cleavage. d. specific gravity.
a. streak.
Wet igneous rock melts at a lower temperature than the dry version of that same rock because a. the addition of volatiles in wet rocks lowers their melting temperature. b. they occur on the sea floor, where temperatures are already cold. c. dry igneous rocks are made of more felsic minerals. d. wet igneous rocks form at shallower depth in the Earth.
a. the addition of volatiles in wet rocks lowers their melting temperature.
Which is NOT one of the ideas Wegener offered to support his theory? a. the existence of the mid-ocean ridge, where sea-floor spreading starts b. the matching of the distribution of similar fossils across oceans c. the matching fit of the outline of some of the continents d. paleoclimatic evidence of extreme climate changes in some areas
a. the existence of the mid-ocean ridge, where sea-floor spreading starts
Identify the FALSE statement. a. Positive magnetic anomalies occur over areas of sea floor when the poles of Earth's magnetic field and the paleopoles preserved in the sea-floor basalt agree; negative anomalies occur when they are opposite each other. b. All polarity chrons are the same length of time; they differ only in the magnetic strengths they represent. c. The series of rock stripes parallel to and bilaterally symmetrical across the mid-ocean ridge record the sequence of Earth's magnetic reversals over time. d. The width of each rock stripe is a measure of how long the polar direction remained constant.
b. All polarity chrons are the same length of time; they differ only in the magnetic strengths they represent.
Which of the following is NOT a characteristic of a rock? a. It is a coherent mass. b. It has a definable chemical composition. c. It is a naturally occurring material. d. It is a collection of minerals or a body of glass.
b. It has a definable chemical composition.
Which of the following statements is FALSE? a. Ocean basins get wider as a result of sea-floor spreading. b. Ocean floor is created by the process of subduction. c. To keep Earth's surface area constant, the amount of sea-floor spreading must equal the amount of subduction. d. Subduction causes continents to move together; sea-floor spreading moves them apart.
b. Ocean floor is created by the process of subduction.
Bowen's Reaction Series a. shows that minerals crystallize in a random order, with no particular pattern involved. b. allows a geologist to predict what minerals will be found in a given igneous rock. c. is an attempt to explain the logic of formation of sedimentary rocks. d. explains why some compounds use ionic bonds and others have covalent bonding.
b. allows a geologist to predict what minerals will be found in a given igneous rock.
Which of the following statements is FALSE? Diamonds: a. are brought from the mantle to the surface in magma that hardens into kimberlite. b. are found in carrot-shaped structures called pegmatites. c. of industrial quality are used as abrasives. d. that have weathered out of ore bodies can end up in stream gravels.
b. are found in carrot-shaped structures called pegmatites.
Identify the FALSE statement. Bathymetric maps show the following features of the sea floor: a. broad flat abyssal plains at depths of 4 to 5 km below sea level. b. bands of vertical fractures (fracture zones) that run parallel to mid-ocean ridges. c. elongate trenches that reach 8 to 12 km deep. d. chains of seamounts (submarine mountains), some of which are active volcanoes.
b. bands of vertical fractures (fracture zones) that run parallel to mid-ocean ridges.
Granite a. is an extrusive igneous rock. b. is felsic in composition. c. could be found in a lava flow. d. is the coarse-grained equivalent of andesite.
b. is felsic in composition.
Choose the FALSE statement. The age of oceanic crust: a. has been determined by radiometric dating. b. is oldest at the mid-ocean ridge and youngest farthest from the ridge. c. varies with location. d. correlates well with calculated rates of sea-floor spreading.
b. is oldest at the mid-ocean ridge and youngest farthest from the ridge.
Cynognathus, Glossopteris, Mesosaurus, and Lystrosaurus are: a. the names of the most recent periods of magnetic reversal. b. land-dwelling species whose distribution suggested joined continents. c. names of supercontinents that existed before Pangaea. d. distinctive assemblages of rocks.
b. land-dwelling species whose distribution suggested joined continents.
Choose the FALSE statement. Glaciers: a. are slow-moving sheets of ice on land. b. leave deposits of sediment called bathymetries. c. occur today at high altitudes or in polar regions. d. occurred during the late Paleozoic in places they cannot exist today.
b. leave deposits of sediment called bathymetries.
Which of the following is a mineral? a. amber (tree sap) b. oyster shell (CaCO3) c. sugar (formula C6H12O6) d. glass
b. oyster shell (CaCO3)
Which of the following groups of silicate minerals exhibits a single strong cleavage in one direction? a. framework silicates b. sheet silicates c. independent tetrahedra silicates d. single-chain silicates
b. sheet silicates
Which of the following was NOT a line of evidence used by Wegener to develop the theory that continents drift? a. the distribution of fossil species b. the presence of earthquakes in seismic belts along trenches, ridges, and fracture zones c. the location of ancient till deposits and striations that indicated glacial movement toward the interior of continents d. matching mountain chains on continents currently separated by oceans
b. the presence of earthquakes in seismic belts along trenches, ridges, and fracture zones
Which of the following statements is FALSE? Volatiles that come out of the Earth as volcanic products a. were dissolved in the molten rock and released as the surrounding pressure lessened. b. usually consist of 50% sulfur dioxide. c. include water, carbon dioxide, nitrogen, hydrogen, and sulfur dioxide. d. contributed to forming Earth's atmosphere and oceans.
b. usually consist of 50% sulfur dioxide.
Radiometric dating of a magnetic anomaly stripe of rock that is 225 km away from the mid-ocean ridge axis gives an age of 4.5 million years. Assuming a constant rate, sea-floor spreading in this area occurs at a rate of: a. 50 km per year. b. 1,012.5 km per year. c. 5 cm per year. d. 20,000 cm per year.
c. 5 cm per year. (distance from mid-ocean ridge = 225 km) (distance in cm = 225 * 100,000 cms) (22,500,000 cm) (age of magnetic strip = 4.5 million years) (4,500,000 years) (22,500,000 cm / 4,500,000 years) (5 cm/year)
Which of the following statements is TRUE? a. Hydrogen has an atomic mass of 2. b. An isotope of an element has the same atomic mass, but different atomic number. c. Helium has an atomic number of 2. d. The atomic mass of an element is approximately equal to the number of protons in an atom of that element.
c. Helium has an atomic number of 2.
Which of the following statements is NOT true about the ocean floor? a. It is covered by a layer of sediment composed of clay and plankton shells. b. The heat flow through it is greatest at the mid-ocean ridges. c. Oceanic crust contains granite and metamorphic rocks. d. Oceanic crust is quite different from continental crust.
c. Oceanic crust contains granite and metamorphic rocks.
Plate tectonics theory took decades to be accepted because: a. most of Wegener's ideas turned out to be wrong. b. of pure stubbornness by the scientific community. c. Wegener couldn't explain how continents moved. d. climate, fossil distributions, and land shape offered conflicting evidence.
c. Wegener couldn't explain how continents moved.
What are vesicles? a. pieces of wall rock broken off by intruding magma b. large crystals floating in a fine-grained groundmass c. air pockets or bubbles frozen in igneous rocks as gas escaped during cooling d. horizontal igneous intrusions
c. air pockets or bubbles frozen in igneous rocks as gas escaped during cooling
Which of the following statements is FALSE? Crystals: a. have an orderly internal arrangement of atoms arranged in a lattice pattern. b. grow outward from a seed. c. are formed by the high-temperature, extremely rapid process known as solid-state diffusion. d. display symmetry.
c. are formed by the high-temperature, extremely rapid process known as solid-state diffusion.
Choose the FALSE statement. Pangaea: a. means "all land." b. started to break apart during the Mesozoic. c. broke apart due to the force created by Earth's rotation. d. is the name for the most recent supercontinent; others have existed.
c. broke apart due to the force created by Earth's rotation.
The tendency of a mineral to break and produce smooth, curving shell-shaped surfaces is termed: a. luster. b. perfect cleavage. c. conchoidal fracture. d. streak.
c. conchoidal fracture.
Which is not a tectonic setting for igneous activity? a. hot spots b. continental rifts c. continental transform fault zones d. volcanic arcs bordering ocean trenches
c. continental transform fault zones
A continuous, uninterrupted piece of a single mineral that grows in place is called a: a. grain. b. fragment. c. crystal. d. clast.
c. crystal.
Identify the FALSE statement. Early Earth had numerous heat sources for igneous activity, including a. conversion of the kinetic energy of meteorite impact to heat energy. b. conversion of the kinetic energy of iron alloy sinking toward Earth's center to heat energy. c. decay of all of its radioactive elements; almost none remain today. d. conversion of the kinetic energy of colliding planetesimals to heat energy.
c. decay of all of its radioactive elements; almost none remain today.
Choose the FALSE statement. Magnetic anomalies are: a. places where the magnetic field strength is either greater or less than the expected strength. b. termed normal if the atomic dipoles match Earth's current magnetic field. c. found only on the sea floor. d. measured with an instrument called a magnetometer.
c. found only on the sea floor.
Which of the following statements is FALSE? Formation of table salt: a. is, in mineralogic terms, formation of the halide mineral halite. b. takes place when a solution has become saturated. c. is an example of solidification of a melt. d. results in cubic crystals.
c. is an example of solidification of a melt.
Identify the FALSE statement. Magma moves upward toward the Earth's surface a. because it's less dense than the surrounding rock. b. slowly, working its way up through cracks and narrow conduits. c. more quickly as it cools and therefore becomes less viscous. d. because the weight of overlying rock creates pressure that squeezes it up.
c. more quickly as it cools and therefore becomes less viscous.
Identify the FALSE statement. Large igneous provinces (LIPs) a. are places where huge amounts of mafic magma have been erupted or intruded. b. represent special events in Earth's history that may have been caused by superplume activity. c. occur only along continental margins. d. may have profound impacts on the environment, including land, ocean, and atmospheric processes.
c. occur only along continental margins.
Choose the one type of deposit that is not typical of a tropical/subtropical climate. a. coal b. reefs c. till d. salt
c. till
Identify the FALSE statement about making observations about rocks at an outcrop. a. Observing the entire outcrop can provide important information about rock relationships and layering. b. Sand-sized and larger grains can be identified with a hand lens. c. A hand specimen is a small piece of the outcrop that can be examined closely. d. A rock's texture cannot be characterized from a hand specimen; it can only be done in thin section.
d. A rock's texture cannot be characterized from a hand specimen; it can only be done in thin section.
Identify the FALSE statement. Silicates: a. have the silicon-oxygen tetrahedron as their structural unit. b. are a major component of continental crust. c. are classified on the basis of how the tetrahedrons join and share oxygen atoms. d. are a large category of minerals and include the common minerals calcite and dolomite.
d. are a large category of minerals and include the common minerals calcite and dolomite.
Which of the following statements is FALSE? Igneous rocks a. form from the cooling and crystallization of either lava or magma. b. form in great quantity along the mid-ocean ridge. c. were the first rocks to exist on Earth. d. are coarse-grained if they cool extrusively.
d. are coarse-grained if they cool extrusively.
Calcite and aragonite minerals that constitute clam shells are examples of which method of mineral formation? a. solidification of a melt b. precipitation from a solution c. solid-state diffusion d. biomineralization
d. biomineralization
Magmas have a variety of chemical compositions because of all of the following EXCEPT a. they come from a variety of source rocks. b. the rocks that melt to make magma are composed of many minerals, not all of which melt under the same conditions. c. the magma's heat can melt rock from the walls of the magma chamber. d. different magmas formed in different locations remain isolated and never mix.
d. different magmas formed in different locations remain isolated and never mix.
Which of the following statements is FALSE? Mafic minerals a. crystallize at a higher temperature than do silicic minerals. b. are rich in iron and magnesium. c. typically crystallize first out of a melt. d. form rhyolite and granite.
d. form rhyolite and granite.
Which of the following terms has nothing to do with intrusive igneous activity? a. pluton b. batholith c. diapir d. hyaloclastite
d. hyaloclastite
Ocean crust: a. is the same composition as continental crust. b. is the same age as continental crust. c. has not been sampled directly because it is too deep beneath the ocean. d. is covered by a thin blanket of sediment that thickens away from the ridge axis.
d. is covered by a thin blanket of sediment that thickens away from the ridge axis.
Which of the following statements is FALSE? Felsic (or silicic) magma a. crystallizes at the lowest temperatures. b. has about 70% silica and little magnesium and iron. c. is likely to form light tan, pink, or maroon rocks. d. is less viscous than mafic magma.
d. is less viscous than mafic magma.
Identify the FALSE statement. Hot solid rock in the Earth a. may be even hotter than surface lava because of the pressure of overlying rock. b. may melt if volatiles such as water and carbon dioxide are added. c. may melt if heat is transferred to it from hot mantle rock rising up into the crust. d. maintains uniform composition as it melts and becomes magma.
d. maintains uniform composition as it melts and becomes magma.
Which of the following statements is FALSE? Volcanic arcs a. form where subduction takes place. b. are long, curving mountain chains adjacent to deep-ocean trenches. c. can be continental or island-related. d. occur at divergent-plate boundaries.
d. occur at divergent-plate boundaries.
The scheme for classifying rocks is based on: a. mineral (and therefore elemental) composition. b. temperature and pressure. c. the average grain size. d. origin of formation.
d. origin of formation.
Graphite is: a. the polymorph of galena. b. harder than glass. c. pure silicon. d. the lead in the pencil you write with.
d. the lead in the pencil you write with.
Magma may cool and crystallize to become solid igneous rock a. when its volatile content increases. b. more slowly in the presence of circulating groundwater. c. faster if the surface area of the intrusion is small. d. very slowly (centuries to a million years) when it forms a deep pluton.
d. very slowly (centuries to a million years) when it forms a deep pluton.
