1.
In order to produce a commercially viable oil deposit, there must be a source rock, a reservoir rock, a seal rock, and a ____________.
Correct Answer
A. Trap—a geologic configuration that forces oil to pool up and denies it passage to the surface
Explanation
The correct answer is a trap—a geologic configuration that forces oil to pool up and denies it passage to the surface. This explanation states that in order to produce a commercially viable oil deposit, a trap is necessary. A trap is a geologic configuration that prevents oil from escaping to the surface and instead causes it to accumulate and form a pool. This is important because without a trap, the oil would not be able to be extracted and utilized.
2.
Chemically, oil and gas are both ____________
Correct Answer
A. Hydrocarbons
Explanation
Oil and gas are both chemically classified as hydrocarbons. Hydrocarbons are organic compounds composed of hydrogen and carbon atoms. Oil and gas are formed from the remains of ancient plants and animals that have been subjected to high pressure and temperature over millions of years. These organic materials undergo a process called diagenesis, which converts them into hydrocarbons. Therefore, hydrocarbons are the correct answer as they accurately describe the chemical composition of oil and gas.
3.
Which fossil fuel, oil or natural gas, is found at greater depths within Earth, and why?
Correct Answer
A. Gas, because it is more stable at high temperatures
Explanation
Gas is found at greater depths within Earth compared to oil because it is more stable at high temperatures. As the Earth's temperature increases with depth, gas remains in a gaseous state due to its higher stability at high temperatures. On the other hand, oil is more stable at low pressures, which means it is found at shallower depths where the pressure is lower.
4.
Shale, salt, and fine-grained limestone that is not fractured are
all good candidates to serve as ____________ within an oil field.
Correct Answer
B. A seal rock
Explanation
Shale, salt, and fine-grained limestone that is not fractured can serve as seal rocks within an oil field. Seal rocks are impermeable formations that prevent the upward migration of oil and gas, acting as a barrier or cap to trap hydrocarbons within a reservoir rock. These types of rocks have low permeability and porosity, making them effective in trapping and preserving hydrocarbons underground.
5.
The oil window (temperature range wherein organic matter is
converted to petroleum without destroying it) lies between ____________.
Correct Answer
C. 90 to 160 °C
Explanation
The oil window refers to the temperature range in which organic matter is converted into petroleum without being destroyed. In this case, the correct answer is 90 to 160 °C. This means that the conversion process occurs within this specific temperature range, indicating the conditions necessary for the formation of petroleum.
6.
Most coal is mined from ____________, which develop and preserve the thick sedimentary sequences necessary for deep burial.
Correct Answer
C. Basins
Explanation
Coal is primarily formed from the remains of plants that have been buried and subjected to heat and pressure over millions of years. These conditions are typically found in basins, which are large depressions in the Earth's surface where sediments accumulate. Basins provide the necessary environment for the formation and preservation of thick sedimentary sequences, which are essential for the deep burial required to create coal deposits. Therefore, most coal is mined from basins.
7.
U-235, the isotope of uranium commonly utilized in nuclear power plants, is ____________.
Correct Answer
B. Rare even in uranium oxide deposits, and thus usable reactor fuel must be enriched with respect to this isotope
Explanation
U-235, the isotope of uranium commonly utilized in nuclear power plants, is rare even in uranium oxide deposits, and thus usable reactor fuel must be enriched with respect to this isotope. This means that U-235 is not commonly found in nature in large quantities. To use U-235 as fuel in nuclear reactors, it needs to be enriched, which involves increasing the concentration of U-235 in the uranium fuel. This enrichment process is necessary because U-235 is not naturally abundant enough to sustain a nuclear reaction on its own.
8.
The first ores which were widely smelted by humans to produce metal were those of ____________.
Correct Answer
B. Copper
Explanation
Copper was the first metal to be widely smelted by humans. Smelting is the process of extracting metal from its ore by heating and melting it. Copper was easily accessible and had desirable properties such as malleability and conductivity, making it an ideal metal for early human civilizations. It was used to create tools, weapons, and decorative items. While other metals like bronze, gold, and iron were also smelted later on, copper was the first metal to be extensively utilized by humans.
9.
Commercial ore deposits are most likely to be found associated with ____________.
Correct Answer
D. Igneous rocks
Explanation
Commercial ore deposits are most likely to be found associated with igneous rocks. This is because igneous rocks are formed from the solidification of molten material, which can contain concentrated minerals and metals. As the molten material cools and solidifies, these minerals and metals can crystallize and accumulate, forming valuable ore deposits. In contrast, thick basinal sandstones and shales, blueschists, and evaporite sequences are not typically associated with the formation of commercial ore deposits.
10.
Mineral-rich veins within plutons, deposited by hot groundwater into fractures within the rock, characterize ____________.
Correct Answer
B. Hydrothermal deposits
Explanation
Hydrothermal deposits are characterized by mineral-rich veins within plutons that are formed when hot groundwater deposits minerals into fractures within the rock. This process occurs in areas where there is intense heat and water circulation, such as near volcanic activity or deep underground. The minerals in hydrothermal deposits are often valuable and can include metals such as gold, silver, and copper.
11.
Which ore minerals are commonly found in ancient sedimentary deposits that are 2 billion years old?
Correct Answer
B. iron oxides
Explanation
Iron oxides are commonly found in ancient sedimentary deposits that are 2 billion years old. This is because iron is a highly reactive element and readily combines with oxygen in the presence of water to form iron oxides. Over time, these iron oxides can accumulate and become concentrated in sedimentary deposits. Additionally, iron oxides are often associated with ancient banded iron formations, which are sedimentary rocks that contain alternating layers of iron-rich minerals and silica. These formations are commonly found in rocks that were deposited during the Precambrian era, which spans from about 4.6 billion to 541 million years ago.
12.
Which mineral resources are considered renewable?
Correct Answer
D. No mineral resources are renewable
Explanation
The correct answer is that no mineral resources are renewable. This means that once mineral resources are extracted and used, they cannot be replenished or replaced. Unlike renewable resources, such as solar or wind energy, mineral resources are finite and can be depleted over time. Therefore, it is important to use mineral resources responsibly and explore alternative options for sustainable resource management.
13.
The United States has active mines within its boundaries that are
sufficient to maintain a steady supply of all strategically important
metals.
Correct Answer
B. False
Explanation
The statement is false because the United States does not have active mines within its boundaries that are sufficient to maintain a steady supply of all strategically important metals. The country relies on imports for many of these metals, which are crucial for various industries and national security.
14.
As suggested by the name “earthquake” the release of seismic energy
as waves is unique to our planet and has not been found to occur in any
other body of our solar system.
Correct Answer
B. False
Explanation
The explanation for the given answer is that the statement is incorrect. Earthquakes are not unique to our planet and seismic activity has been observed on other celestial bodies in our solar system, such as the moon and certain moons of Jupiter and Saturn. Therefore, the statement that seismic energy release as waves only occurs on Earth is false.
15.
If, during an earthquake, a hanging wall slides upward relative to
a footwall, the fault is termed ____________ if the fault is steep
(closer to vertical than horizontal).
Correct Answer
B. Reverse
Explanation
If the hanging wall slides upward relative to the footwall during an earthquake and the fault is steep (closer to vertical than horizontal), it is termed as a "reverse" fault. In a reverse fault, the hanging wall moves up and over the footwall, which is the opposite of what happens in a normal fault where the hanging wall moves down relative to the footwall. This type of faulting is commonly associated with compressional forces and is often found in areas of mountain building and tectonic collision.
16.
An earthquake occurs with an epicenter in the town of New Madrid,
Missouri, in the interior of the North American Plate. Where might the
hypocenter of this earthquake plausibly be found?
Correct Answer
A. 20 km beneath New Madrid
Explanation
The hypocenter of the earthquake is likely to be found 20 km beneath New Madrid. The term "hypocenter" refers to the point within the Earth where the seismic energy is released during an earthquake. Since the epicenter is in New Madrid, it is plausible that the hypocenter would be located directly beneath it.
17.
Earthquake waves which pass through the interior of Earth are termed ____________.
Correct Answer
D. Body waves
Explanation
Body waves are seismic waves that travel through the interior of the Earth. They include two types: P-waves (primary waves) and S-waves (secondary waves). P-waves are compressional waves that travel faster and can pass through both solids and liquids, while S-waves are shear waves that travel slower and can only pass through solids. These body waves are responsible for the initial shaking felt during an earthquake and provide valuable information about the Earth's interior structure. Surface waves, on the other hand, travel along the Earth's surface and are responsible for the most destructive effects of an earthquake.
18.
Surface waves ____________.
Correct Answer
A. Produce most of the damage to buildings during earthquakes
Explanation
Surface waves are a type of seismic waves that travel along the Earth's surface. These waves cause the most damage to buildings during earthquakes because they have a larger amplitude and longer duration compared to other types of seismic waves. The shaking caused by surface waves can cause buildings to collapse, leading to significant destruction and loss of life.
19.
Earthquakes that occur in a band called a ____________ can be used to track the motion of subducted oceanic lithosphere.
Correct Answer
B. Wadati-Benioff zone
Explanation
The correct answer is the Wadati-Benioff zone. Earthquakes that occur in this zone, which is located beneath a subduction zone, can be used to track the motion of subducted oceanic lithosphere. The Wadati-Benioff zone is characterized by a steeply dipping band of earthquakes that extends from the surface down into the mantle. This zone provides valuable information about the subduction process and helps scientists understand the dynamics of plate tectonics.
20.
Long-term prediction of earthquake behavior ____________.
Correct Answer
D. All of the above
Explanation
Long-term prediction of earthquake behavior involves multiple factors and considerations. It is based on past earthquake activity, as studying historical seismic events can provide insights into patterns and trends. It also works on the principle that zones of past seismicity will be active in the future, as areas that have experienced earthquakes before are likely to experience them again. Additionally, long-term prediction includes the notion of seismic gaps, which are areas where an earthquake has not occurred for a significant period, suggesting that it may be "overdue." Therefore, the correct answer is "all of the above" as all these factors are taken into account in long-term earthquake prediction.
21.
Which of the world’s major cities has suffered tremendous
earthquake damage in the past not because it is located at a plate
boundary (it is not), but rather because it is built atop a basin of
ancient lakebed sediments that rhythmically rock back and forth when
agitated by seismic waves of a characteristic frequency?
Correct Answer
D. Mexico City
Explanation
Mexico City has suffered tremendous earthquake damage in the past not because it is located at a plate boundary, but rather because it is built atop a basin of ancient lakebed sediments. These sediments have the ability to rhythmically rock back and forth when agitated by seismic waves of a characteristic frequency. This phenomenon, known as liquefaction, can amplify the shaking during an earthquake and cause significant damage to buildings and infrastructure.
22.
Seismic rays follow curve paths in Earth's interior due to ____________.
Correct Answer
D. Gradual changes in density with depth beneath the surface
Explanation
Seismic rays follow curved paths in Earth's interior due to gradual changes in density with depth beneath the surface. As seismic waves travel through the Earth, they encounter different layers of rock with varying densities. These density variations cause the waves to refract or bend, leading to curved paths. This phenomenon is known as seismic refraction. The gradual changes in density with depth play a significant role in determining the path of seismic rays as they travel through the Earth's interior.
23.
Seismologist know that the outer core is liquid due to the presence of ______________.
Correct Answer
E. Both D and B
Explanation
The presence of a S-wave "shadow" zone for seismometers situated on the far side of the Earth from earthquake hypocenters and a P-wave "shadow" zone for seismometers situated between 104° and 140° from earthquake hypocenters suggests that the outer core is liquid. This is because S-waves cannot travel through liquids, so the presence of a S-wave shadow zone indicates that there must be a liquid layer in the outer core. Similarly, the P-wave shadow zone suggests the presence of a liquid layer as well. Therefore, both D and B provide evidence for the outer core being liquid.
24.
The word "metamorphism" literally refers to
Correct Answer
D. Change.
Explanation
The word "metamorphism" literally refers to change. This term is commonly used in geology to describe the process of transformation that rocks undergo due to heat, pressure, and other environmental factors. It does not refer to any specific philosophical concept or physical movement towards the middle. Instead, it simply signifies a general alteration or modification.
25.
When rocks are metamorphosed,
Correct Answer
A. The original minerals are recrystallized in the solid state, and they are sometimes replaced by a new set of minerals.
Explanation
When rocks undergo metamorphism, the original minerals within the rock undergo recrystallization while remaining in the solid state. This means that the minerals rearrange and reform into new crystal structures without melting. Additionally, during metamorphism, the original minerals can be replaced by a new set of minerals, which can result in changes in the composition and appearance of the rock. This process is known as metasomatism. Therefore, the given answer accurately describes the changes that occur during rock metamorphism.
26.
A rock with a well-developed foliation
Correct Answer
C. Has platty mineral grains (like micas) aligned parallel to each other, causing the rock to break into flat slabs.
Explanation
The correct answer is that a rock with a well-developed foliation has platty mineral grains (like micas) aligned parallel to each other, causing the rock to break into flat slabs. This is because foliation is the alignment of minerals or mineral bands in a rock, and the presence of platty minerals like micas can cause this alignment. As a result, the rock exhibits a layered or slab-like structure, making it prone to breaking into flat slabs.
27.
If a basalt is metamorphosed, the following rock types could develop in this order in response to increasing temperature:
Correct Answer
D. Greenschist : ampHibolite
Explanation
The given correct answer states that greenschist would develop before amphibolite in response to increasing temperature during the metamorphism of basalt. This implies that greenschist is the lower grade metamorphic rock and amphibolite is the higher grade metamorphic rock. This order is consistent with the progressive metamorphic sequence in which rocks undergo increasing levels of heat and pressure.
28.
If a shale is metamorphosed, the following rock types develop in this order in response to increasing temperature:
Correct Answer
B. Slate : pHyllite : schist : gneiss
cooler → hotter
Explanation
As the temperature increases, the shale undergoes metamorphism and transforms into different rock types. The process starts with the formation of slate, which is a low-grade metamorphic rock. As the temperature continues to rise, the slate transforms into phyllite, which has a slightly higher metamorphic grade. Further increase in temperature leads to the formation of schist, which is a medium-grade metamorphic rock. Finally, with the highest temperature, the schist transforms into gneiss, which is a high-grade metamorphic rock. Therefore, the correct order of rock types in response to increasing temperature is slate, phyllite, schist, and gneiss.
29.
You have discovered an outcrop of mica schist, and you know that
this is a metamorphic rock. Which of the following rocks could have
been metamorphosed to form this mica schist?
Correct Answer
D. Shale
Explanation
Shale could have been metamorphosed to form mica schist. Shale is a sedimentary rock composed of clay minerals, and under high temperature and pressure conditions, it can undergo metamorphism and transform into mica schist. This process involves recrystallization of the clay minerals and the formation of mica minerals, giving the rock its characteristic foliated texture. Limestone, ignimbrite, and basalt are not likely to be the parent rocks of mica schist as they have different mineral compositions and textures.
30.
Contact metamorphism would occur when
Correct Answer
C. Magma is emplaced adjacent to relatively cool sedimentary rocks.
Explanation
Contact metamorphism occurs when magma is emplaced adjacent to relatively cool sedimentary rocks. This process involves the heat from the magma being transferred to the surrounding rocks, causing them to undergo metamorphic changes. The temperature increase and the chemical reactions between the magma and the rocks lead to the formation of new minerals and the alteration of the existing ones. This type of metamorphism typically occurs in localized areas around the igneous intrusion and can result in the formation of characteristic metamorphic rocks such as hornfels.
31.
The best plate-tectonic environment for making blueschists (high pressure, lower temperature) metamorphic rocks is
Correct Answer
C. Subduction zones.
Explanation
Blueschists are high-pressure, low-temperature metamorphic rocks that form when oceanic crust is subducted beneath another tectonic plate. Subduction zones are the best plate-tectonic environment for the formation of blueschists because they involve the collision of two plates, with one being forced beneath the other. This process subjects the oceanic crust to extreme pressure and lower temperatures, which are ideal conditions for the formation of blueschists. Hot spots, himalayan-type orogens, and mid-ocean ridges do not typically have the same combination of high pressure and low temperature required for the formation of blueschists.
32.
One of the main differences between a gneiss and a schist is that
Correct Answer
A. Gneisses have more feldspar and less mica than schists.
Explanation
Gneisses and schists are both types of metamorphic rocks, but they have different mineral compositions. Gneisses have more feldspar and less mica compared to schists. This difference in mineral content is one of the main distinguishing factors between the two rock types.
33.
Seafloor metamorphism
Correct Answer
D. All of the above.
Explanation
Seafloor metamorphism is a process where seawater interacts with hot seafloor rocks, resulting in the formation of metamorphic rocks. These rocks typically do not have foliation. This process primarily takes place at or near mid-ocean ridges and transform faults. Therefore, the correct answer is "all of the above" as it encompasses all the statements mentioned.
34.
The breakdown of exposed rock into small fragments and dissolved ions is termed
Correct Answer
C. Weathering
Explanation
Weathering is the correct answer because it refers to the process of breaking down exposed rock into smaller fragments and dissolved ions. This can occur through various mechanisms such as physical weathering (e.g. freeze-thaw cycles, abrasion) and chemical weathering (e.g. oxidation, hydrolysis). Weathering is an important step in the overall process of erosion and sedimentation, as it prepares the rock material to be transported and deposited by other geological processes.
35.
Frost wedging, root wedging, and salt wedging are all examples of ____________.
Correct Answer
B. pHysical weathering
Explanation
Frost wedging, root wedging, and salt wedging are all examples of physical weathering. Physical weathering refers to the breakdown of rocks and minerals into smaller pieces without any chemical change. Frost wedging occurs when water seeps into cracks in rocks, freezes, and expands, causing the rock to break apart. Root wedging happens when plant roots grow into cracks in rocks, exerting pressure and causing them to break. Salt wedging occurs when saltwater seeps into rocks, evaporates, and leaves behind salt crystals that expand and break the rock. These processes all involve physical forces that break down rocks without altering their chemical composition, making them examples of physical weathering.
36.
Hydrolysis, oxidation, and hydration are all examples of ____________.
Correct Answer
A. Chemical weathering
Explanation
Hydrolysis, oxidation, and hydration are all processes that involve the chemical breakdown of rocks and minerals. Chemical weathering refers to the alteration and decomposition of rocks through chemical reactions, such as the reaction of water with minerals (hydrolysis), the reaction of minerals with oxygen (oxidation), and the reaction of minerals with water (hydration). These processes result in the weakening and disintegration of rocks over time. Therefore, the correct answer is chemical weathering.
37.
Spheroidal weathering occurs when ____________.
Correct Answer
B. Chemical weathering attacks corners and edges of rock more rapidly than its interior
Explanation
Spheroidal weathering occurs when chemical weathering attacks corners and edges of rock more rapidly than its interior. This process causes the rock to gradually round off and form spherical shapes. It is a type of weathering that occurs in areas with high moisture and temperature fluctuations. The chemical reactions weaken the corners and edges of the rock, making them more susceptible to erosion. Over time, the rock erodes and takes on a rounded shape.
38.
Caliche is most commonly found in which type of environments?
Correct Answer
B. Deserts
Explanation
Caliche is most commonly found in deserts. Caliche is a type of soil or sediment that is formed through the accumulation of calcium carbonate in arid environments. Deserts have a lack of water and high evaporation rates, which leads to the concentration of minerals like calcium carbonate in the soil. This accumulation over time results in the formation of caliche. Therefore, deserts provide the ideal conditions for the development of caliche.
39.
Laterite soils are most commonly found in which type of environments?
Correct Answer
D. Tropical rain forests
Explanation
Laterite soils are most commonly found in tropical rain forests. This is because the high temperatures and heavy rainfall in tropical rainforest environments cause the rapid weathering of rocks and minerals. As a result, the soil becomes rich in iron and aluminum oxides, giving it a reddish color. The intense weathering also leads to the leaching of nutrients, making the soil relatively infertile. These conditions are ideal for the formation of laterite soils, which are characteristic of tropical rainforest environments.
40.
Because the velocity of sediment settling (deposition) is positively related to grain size
for waterborne sediments, fluvial deposits are more likely than glacial deposits to
____________.
Correct Answer
A. Be well sorted
Explanation
Fluvial deposits, which are formed by flowing water, are more likely to be well sorted because the velocity of sediment settling is positively related to grain size. This means that smaller grains settle more slowly than larger grains. As a result, when sediment is transported by water, the larger grains settle first and the smaller grains settle later. This sorting process leads to well-sorted deposits where grains of similar sizes are grouped together. Therefore, fluvial deposits are more likely to be well sorted compared to glacial deposits, which are formed by ice and do not undergo the same sorting process.
41.
It is unusual for ____________ to carry grains larger than sand.
Correct Answer
B. Wind
Explanation
Wind is the correct answer because it is unusual for wind to carry grains larger than sand. Wind is not typically strong enough to carry larger grains, such as rocks or pebbles. Water, on the other hand, can carry larger grains, such as gravel or boulders, depending on its speed and force. Ice can also carry larger grains, as it can freeze around larger objects and transport them. Therefore, wind stands out as the most unlikely candidate for carrying grains larger than sand.
42.
If water is the transport medium of sediment, the grain size of sedimentary deposits
most closely indicates the ____________.
Correct Answer
A. Velocity of the water at the moment the sediment settled to the bottom
Explanation
The grain size of sedimentary deposits most closely indicates the velocity of the water at the moment the sediment settled to the bottom. This is because the size of the sediment particles is directly related to the energy of the water that transported them. Higher velocity water can carry larger and heavier particles, while lower velocity water can only carry smaller and lighter particles. Therefore, by examining the grain size of sedimentary deposits, we can infer the velocity of the water at the time of deposition.
43.
The difference between breccia and conglomerate is that conglomerate ____________.
Correct Answer
C. Possesses more rounded grains than breccia
Explanation
Conglomerate possesses more rounded grains than breccia. This is because conglomerate is formed from rounded pebbles and rocks that have been transported and deposited by water, resulting in the rounding of the grains. On the other hand, breccia is formed from angular fragments that have been cemented together, which gives it a more angular appearance. Therefore, the main difference between the two is the shape of the grains, with conglomerate having more rounded grains than breccia.
44.
Ash, cinders, and blocks are all types of _________.
Correct Answer
A. Volcanoclastic debris
Explanation
Ash, cinders, and blocks are all types of volcanic materials that are produced during volcanic eruptions. These materials are known as volcanoclastic debris, which refers to the fragments of rock and other materials that are ejected from a volcano during an eruption. These fragments can vary in size and composition, and they can be carried by volcanic gases, lava flows, or explosive eruptions. Volcanoclastic debris is an important component of volcanic activity and can provide valuable information about the eruptive history and behavior of a volcano.
45.
Volcanic Bombs are ________.
Correct Answer
A. Pyroclastic blocks that acquire aerodynamic shapes during flight out of the volcanic vent
Explanation
Volcanic bombs are pyroclastic blocks that acquire aerodynamic shapes during flight out of the volcanic vent. This means that as they are ejected from the volcano, they are shaped by the air resistance and gravity, giving them a streamlined and often elongated form. This process occurs due to the high velocity at which the volcanic material is expelled from the vent. The term "pyroclastic" refers to the fragments of rock and lava that are ejected during volcanic eruptions.
46.
Used in highly hazardous volcanoes to mitigate volcanic hazards via small controlled eruptions
Correct Answer
B. A submarine hot-spot located along a mid-ocean ridge
Explanation
A submarine hot-spot located along a mid-ocean ridge can be used in highly hazardous volcanoes to mitigate volcanic hazards via small controlled eruptions. This is because mid-ocean ridges are areas where tectonic plates are moving apart, allowing magma to rise to the surface and form underwater volcanoes. By intentionally inducing small eruptions at these hot-spots, the pressure and buildup of magma can be released in a controlled manner, reducing the risk of larger and more destructive eruptions.
47.
Which national park is home to a large volcanic caldera formed through a very large explosive eruption 640,000 years ago?
Correct Answer
D. Yellowstone
Explanation
Yellowstone is the correct answer because it is home to a large volcanic caldera formed through a very large explosive eruption 640,000 years ago. The eruption resulted in the formation of the Yellowstone Caldera, which is one of the largest active volcanic systems in the world. The caldera is characterized by its geothermal features such as geysers, hot springs, and mud pots, making Yellowstone a unique and geologically significant national park.
48.
Olympus Mons, the largest known volcano in the Universe, is found on ____________, and is an example of a ____________.
Correct Answer
A. Mars / shield
Explanation
Olympus Mons, the largest known volcano in the Universe, is found on Mars. It is an example of a shield volcano. Shield volcanoes are characterized by their broad, gently sloping sides and large basaltic lava flows. Olympus Mons fits this description as it has a wide base and a low profile, with lava flows that extend for hundreds of kilometers.
49.
Whether an eruption will primarily produce lava flows or pyroclastic debris is influenced by __________.
Correct Answer
D. All of the above
Explanation
The correct answer is "all of the above". The viscosity of the lava, the composition of the lava, and the proportion of volatiles within the lava all play a role in determining whether an eruption will primarily produce lava flows or pyroclastic debris. The viscosity of the lava affects how easily it can flow, with more viscous lava tending to form lava flows. The composition of the lava can determine its explosiveness, with more silica-rich lava being more explosive and producing pyroclastic debris. The proportion of volatiles, such as water vapor and gases, can also influence the explosiveness of the eruption.
50.
Explosive or voluminous eruptions may cause the volcano to collapse
on the floor of the (now empty) magma chamber, producing a broad
depression termed a ____________.
Correct Answer
D. Caldera
Explanation
Explosive or voluminous eruptions can release a significant amount of magma and gases from the volcano, causing the volcano to collapse. This collapse forms a large depression called a caldera. A caldera is typically much larger than a crater and is formed when the magma chamber beneath the volcano is emptied, resulting in the collapse of the volcano's surface.