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Volcanologists primarily categorize volcanic eruptions based on the type of material expelled, rather than by observed behaviors at famous volcanoes.
Answer: False
Explanation: Volcanologists frequently categorize volcanic eruptions by naming them after famous volcanoes where specific behaviors have been observed, rather than solely by the type of material expelled.
Phreatic eruptions are characterized by the release of new magma due to the direct interaction of magma and water.
Answer: False
Explanation: Phreatic eruptions are steam-blast events that only eject fragments of pre-existing solid rock, without the release of new magma. The direct interaction of magma and water leading to new magma release characterizes phreatomagmatic eruptions.
Peléan eruptions are generally considered weaker than Strombolian eruptions but stronger than Hawaiian eruptions.
Answer: False
Explanation: Peléan eruptions are generally considered stronger than both Strombolian and Hawaiian eruptions, ranking higher on the scale of eruptive strength.
The Volcanic Explosivity Index (VEI) is an order-of-magnitude scale, meaning each interval represents a tenfold increase in magnitude.
Answer: True
Explanation: The Volcanic Explosivity Index (VEI) is indeed an order-of-magnitude scale, where each successive interval signifies a tenfold increase in the eruption's magnitude, similar to the Richter scale for earthquakes.
Effusive eruptions are characterized by gas-driven explosions that forcefully propel magma and tephra into the atmosphere.
Answer: False
Explanation: Effusive eruptions are characterized by the outpouring of lava without significant explosive activity. Gas-driven explosions that forcefully propel magma and tephra are characteristic of *explosive* eruptions.
George P. L. Walker identified 'temperature' as one of the five important properties for studying the products of explosive eruptions.
Answer: False
Explanation: George P. L. Walker identified magnitude, intensity, dispersive power, violence, and destructive potential as the five important properties for studying explosive eruption products, not temperature.
The majority of volcanic eruptions have a Volcanic Explosivity Index (VEI) between 3 and 5.
Answer: False
Explanation: The vast majority of volcanic eruptions have a Volcanic Explosivity Index (VEI) between 0 and 2, indicating relatively weaker events, not between 3 and 5.
A VEI 0 eruption is characterized by a plume height greater than 100 meters and an eruptive volume of 1,000 cubic meters.
Answer: False
Explanation: A VEI 0 eruption is characterized by a plume height *less than* 100 meters and an eruptive volume of 1,000 cubic meters.
The 1980 eruption of Mount St. Helens was a notable example of a VEI 5 event, characterized by a plume height greater than 25 kilometers.
Answer: True
Explanation: The 1980 eruption of Mount St. Helens is indeed a prominent example of a VEI 5 event, featuring a plume height that exceeded 25 kilometers and a significant eruptive volume.
Magmatic eruptions are exclusively characterized by small lava fountains and do not include catastrophic events like Ultra-Plinian columns.
Answer: False
Explanation: Magmatic eruptions exhibit a wide range of intensities, from small lava fountains to catastrophic Ultra-Plinian columns that can reach over 30 kilometers high.
Both magmatic and phreatomagmatic eruptions are primarily driven by the thermal expansion of gases within the magma.
Answer: False
Explanation: Magmatic eruptions are driven by the thermal expansion of gases within magma, whereas phreatomagmatic eruptions are primarily driven by the thermal contraction of magma upon direct contact with water.
Phreatic eruptions are distinguished by the forceful ejection of newly formed magma along with steam and rock fragments.
Answer: False
Explanation: Phreatic eruptions are distinguished by the forceful ejection of *pre-existing* solid rock fragments and steam, with no newly formed magma being erupted.
Phreatic eruptions always lead to a full magmatic volcanic eruption shortly after their occurrence.
Answer: False
Explanation: Phreatic activity does not always culminate in a full magmatic volcanic eruption; while they can be precursors, the rock edifice may be strong enough to prevent a larger magmatic event.
VEI 8 eruptions, also known as 'Supervolcanic' eruptions, occur approximately every 100 to 500 years.
Answer: False
Explanation: VEI 8, or 'Supervolcanic,' eruptions are extremely rare, estimated to occur with a frequency of approximately every 50,000+ years, not every 100 to 500 years.
How do volcanologists often categorize different types of volcanic eruptions?
Answer: By naming them after famous volcanoes where specific behaviors have been observed.
Explanation: Volcanologists frequently categorize different types of volcanic eruptions by naming them after famous volcanoes where specific behaviors have been observed, such as Hawaiian, Strombolian, or Plinian.
Which of the following is the primary driving mechanism for a magmatic eruption?
Answer: The decompression of gas within magma.
Explanation: Magmatic eruptions are primarily driven by the decompression of dissolved gases within the magma, which causes it to expand and propel material forcefully.
Which two volcanic eruption subtypes are generally considered the weakest in terms of strength?
Answer: Hawaiian and submarine
Explanation: Among the various eruption subtypes, Hawaiian and submarine eruptions are generally considered the weakest in terms of eruptive strength.
What is the range of the Volcanic Explosivity Index (VEI)?
Answer: 0 to 8
Explanation: The Volcanic Explosivity Index (VEI) is a scale that ranges from 0 to 8, quantifying the strength of volcanic eruptions.
What is the defining characteristic of an effusive volcanic eruption?
Answer: The outpouring of lava without significant explosive activity.
Explanation: Effusive volcanic eruptions are defined by the relatively calm outpouring of lava without significant explosive activity, typically resulting in lava flows.
According to George P. L. Walker, which property refers to the total volume of material ejected during an explosive eruption?
Answer: Magnitude
Explanation: According to George P. L. Walker, 'magnitude' refers to the total volume of material ejected during an explosive eruption, one of five important properties for studying such events.
What is the typical VEI range for the vast majority of volcanic eruptions?
Answer: 0 to 2
Explanation: The vast majority of volcanic eruptions typically fall within the Volcanic Explosivity Index (VEI) range of 0 to 2, indicating relatively weaker eruptive events.
What is the minimum eruptive volume for a VEI 5 eruption?
Answer: 1 cubic kilometer
Explanation: A VEI 5 eruption is characterized by a minimum eruptive volume of 1 cubic kilometer, alongside a plume height greater than 25 kilometers.
What is the distinguishing characteristic of phreatic eruptions?
Answer: They only blast out fragments of pre-existing solid rock.
Explanation: The distinguishing characteristic of phreatic eruptions is that they only blast out fragments of pre-existing solid rock from the volcanic conduit, without the eruption of new magma.
What is the estimated frequency of VEI 8, or 'Supervolcanic,' eruptions?
Answer: Approximately every 50,000+ years.
Explanation: VEI 8, or 'Supervolcanic,' eruptions are exceptionally rare, with an estimated frequency of occurring only every 50,000+ years.
Hawaiian eruptions are known for their highly explosive activity and the formation of steep-sided stratovolcanoes.
Answer: False
Explanation: Hawaiian eruptions are known for their calm, effusive activity and typically build broad, low-angle shield volcanoes, not steep-sided stratovolcanoes.
Hawaiian eruptions typically begin with a single, massive explosion from a central vent.
Answer: False
Explanation: Hawaiian eruptions often begin as a 'curtain of fire' along a fissure vent, rather than with a single, massive explosion from a central vent.
A'a lava flows are characterized by a smooth, ropey texture and can transform into Pahoehoe lava if viscosity decreases.
Answer: False
Explanation: A'a lava flows are characterized by a dense, rubble-like texture, while Pahoehoe lava has a smooth, ropey texture. Furthermore, Pahoehoe can transform into A'a, but A'a never reverts to Pahoehoe.
Pele's hair is a type of dense, crystalline rock formed during Hawaiian eruptions.
Answer: False
Explanation: Pele's hair consists of long, thin strands of volcanic glass, formed when small volcanic particles cool quickly in the air and are drawn out by high winds during Hawaiian eruptions, not dense crystalline rock.
Strombolian eruptions are driven by the continuous outpouring of lava without significant explosive activity.
Answer: False
Explanation: Strombolian eruptions are characterized by episodic, explosive bursts driven by the bursting of gas bubbles within the magma, not by the continuous outpouring of lava without significant explosive activity.
Strombolian eruptions primarily form shield volcanoes through the steady accumulation of fluid lava flows.
Answer: False
Explanation: Strombolian eruptions primarily build cinder cones through the accumulation of ejected volcanic bombs and lapilli fragments, whereas shield volcanoes are formed by the steady accumulation of fluid lava flows characteristic of Hawaiian eruptions.
Strombolian eruptions are generally quieter than Hawaiian eruptions and produce sustained eruptive columns.
Answer: False
Explanation: Strombolian eruptions are generally noisier than Hawaiian eruptions and do not produce sustained eruptive columns; instead, they are characterized by episodic bursts.
Strombolian eruptions involve highly viscous magma, leading to high gas pressure buildup and non-aerodynamic fragments.
Answer: False
Explanation: Strombolian eruptions involve lavas with *intermediate* viscosity, which allows gas bubbles to coalesce and burst. Highly viscous magma leading to high gas pressure and non-aerodynamic fragments is characteristic of Vulcanian eruptions.
What type of volcano do Hawaiian eruptions typically build due to their calm, effusive nature?
Answer: Shield volcanoes
Explanation: Due to their calm, effusive nature and the steady production of fluid lava, Hawaiian eruptions typically build large, broad shield volcanoes.
How do Hawaiian eruptions often begin along a fissure vent?
Answer: As a 'curtain of fire'.
Explanation: Hawaiian eruptions often commence along a fissure vent as a 'curtain of fire,' a line of vent eruptions, before concentrating at a few central vents.
What unique volcanological object is formed when small volcanic particles cool quickly in the air and are drawn out into long strands by high winds during Hawaiian eruptions?
Answer: Pele's hair
Explanation: Pele's hair consists of long, thin strands of volcanic glass formed during Hawaiian eruptions when small volcanic particles cool rapidly in the air and are stretched by high winds.
What drives the explosive activity in a Strombolian eruption?
Answer: The bursting of gas bubbles within the magma.
Explanation: The explosive activity in a Strombolian eruption is driven by the accumulation and bursting of gas bubbles ('gas slugs') within the magma column, which release magma into the air.
What type of volcanic cone is typically built by the steady accumulation of volcanic bombs and lapilli fragments from Strombolian eruptions?
Answer: Cinder cone
Explanation: Strombolian eruptions, through the steady accumulation of ejected volcanic bombs and lapilli fragments, typically build cinder cones.
Which of the following is a key difference between Strombolian and Hawaiian eruptions?
Answer: Strombolian eruptions generate fewer molten lava flows.
Explanation: A key difference is that Strombolian eruptions generate fewer molten lava flows compared to Hawaiian eruptions, which are characterized by extensive effusive lava flows.
Ultra-Plinian eruptions are characterized by plume heights less than 25 kilometers and occur approximately every 10-15 years.
Answer: False
Explanation: Ultra-Plinian eruptions are characterized by plume heights *exceeding* 25 kilometers and occur with extreme rarity, approximately every 50,000+ years, not every 10-15 years.
Vulcanian eruptions are characterized by highly aerodynamic lava fragments due to low magma viscosity.
Answer: False
Explanation: Vulcanian eruptions are characterized by non-aerodynamic lava fragments due to the magma's higher viscosity and the incorporation of crystalline material from the fractured caprock.
Bread-crust bombs form when the interior of an ejected lava fragment cools and contracts faster than its exterior, causing cracks.
Answer: False
Explanation: Bread-crust bombs form when the *exterior* of an ejected lava fragment cools rapidly, while the *interior* continues to cool and vesiculate, causing the expanding center to crack the solidified exterior.
The most dangerous characteristic of a Peléan eruption is the slow-moving, effusive lava flows it produces.
Answer: False
Explanation: The most dangerous characteristic of a Peléan eruption is the formation of fast-moving pyroclastic flows, not slow-moving, effusive lava flows.
The growth of a 'lava spine' in a volcano's summit is an indicator that a Peléan eruption has already concluded.
Answer: False
Explanation: The growth of a 'lava spine' or 'Peléan spine' in a volcano's summit is an early sign of an *impending* Peléan eruption, not an indication that it has concluded.
Peléan eruptions are characterized by several smaller, discrete explosions, similar to Vulcanian activity, but with less overall force.
Answer: False
Explanation: Peléan eruptions are characterized by one large, powerful explosion, contrasting with the several smaller, discrete explosions typical of Vulcanian activity.
Plinian eruptions are named after Pliny the Elder, who was a victim of the 79 AD Vesuvius eruption.
Answer: False
Explanation: Plinian eruptions are named after Pliny the Younger, who chronicled the 79 AD eruption of Mount Vesuvius, not Pliny the Elder.
The distinctive feature of a Plinian eruption is its broad, low-relief lava flows that spread across the landscape.
Answer: False
Explanation: The distinctive feature of a Plinian eruption is its massive eruptive column, which can reach high into the atmosphere, not broad, low-relief lava flows.
Plinian eruptions are typically associated with low-viscosity basaltic lavas, which allow gases to escape easily.
Answer: False
Explanation: Plinian eruptions are typically associated with volatile-rich dacitic to rhyolitic lavas, which are more viscous and effectively trap gases, leading to greater explosive potential.
Lahars are slow-moving lava flows that solidify into dense rock formations.
Answer: False
Explanation: Lahars are fast-moving mudflows with the consistency of wet concrete, formed by the mixing of meltwater and tephra, not slow-moving lava flows.
The primary hazard of phreatic eruptions is the extensive lava flows they produce.
Answer: False
Explanation: Phreatic eruptions do not produce lava flows, as they involve no new magma. Their primary hazards include base surges, lahars, avalanches, volcanic block 'rain,' and the release of deadly toxic gases.
The 1902 eruption of Mount Pelée was significant for being the first recorded instance of a large-scale effusive basaltic lava flow.
Answer: False
Explanation: The 1902 eruption of Mount Pelée was significant as the namesake for Peléan eruptions, characterized by deadly pyroclastic flows, not as the first recorded instance of a large-scale effusive basaltic lava flow.
What is the highest Volcanic Explosivity Index (VEI) represented by an 'Ultra-Plinian' eruption?
Answer: VEI 8
Explanation: An 'Ultra-Plinian' eruption represents the strongest type of volcanic event, corresponding to a Volcanic Explosivity Index (VEI) of 8.
What makes the ejected lava fragments in Vulcanian eruptions distinct from those in Strombolian eruptions?
Answer: They are not aerodynamic due to higher magma viscosity and crystalline material.
Explanation: Ejected lava fragments in Vulcanian eruptions are distinct because they are non-aerodynamic, a result of the magma's higher viscosity and the greater incorporation of crystalline material from the fractured caprock, unlike the more aerodynamic fragments of Strombolian eruptions.
How do 'bread-crust bombs' typically form during Vulcanian eruptions?
Answer: The exterior cools rapidly while the interior continues to cool and vesiculate, causing the exterior to crack.
Explanation: 'Bread-crust bombs' form during Vulcanian eruptions when the exterior of an ejected lava fragment cools rapidly, while the interior continues to cool and vesiculate, causing the expanding center to crack the solidified exterior.
What is the most dangerous characteristic of a Peléan eruption?
Answer: The formation of fast-moving pyroclastic flows.
Explanation: The most dangerous characteristic of a Peléan eruption is the formation of fast-moving pyroclastic flows, which can travel at tremendous speeds and cause widespread destruction.
What does the growth of a 'lava spine' or 'Peléan spine' in a volcano's summit signify?
Answer: An early sign of an impending Peléan eruption.
Explanation: The growth of a 'lava spine' or 'Peléan spine' in a volcano's summit is an early indicator of an impending Peléan eruption, preceding the collapse of the lava dome that drives the explosive event.
Plinian eruptions are named after which historical figure who chronicled the 79 AD eruption of Mount Vesuvius?
Answer: Pliny the Younger
Explanation: Plinian eruptions are named after Pliny the Younger, who famously chronicled the catastrophic 79 AD eruption of Mount Vesuvius.
What is the distinctive feature of a Plinian eruption?
Answer: A massive eruptive column reaching high into the atmosphere.
Explanation: The distinctive feature of a Plinian eruption is its massive eruptive column, which can extend tens of kilometers into the atmosphere, formed by the explosive release of dissolved volatile gases.
What type of lavas are typically associated with highly explosive Plinian eruptions?
Answer: Volatile-rich dacitic to rhyolitic lavas.
Explanation: Highly explosive Plinian eruptions are typically associated with volatile-rich dacitic to rhyolitic lavas, which are more viscous and effectively trap gases, leading to greater explosive potential.
How are lahars formed during Plinian eruptions?
Answer: By the mixing of meltwater from snow/ice with tephra.
Explanation: During Plinian eruptions, lahars are formed when hot ejected material melts snow and ice deposits on the volcano, and this meltwater mixes with tephra (volcanic ash and rock fragments) to create fast-moving mudflows.
How does the viscosity of magma influence the characteristics of Strombolian versus Vulcanian eruptions?
Answer: Strombolian eruptions involve intermediate viscosity magma, allowing gas bubbles to burst, while Vulcanian eruptions involve more viscous magma leading to higher gas pressure.
Explanation: Strombolian eruptions are characterized by intermediate viscosity magma, which permits gas bubbles to coalesce and burst. In contrast, Vulcanian eruptions involve more viscous magma, hindering gas escape and leading to higher pressure buildup and more explosive events.
Thermal expansion from chilling upon contact with water is a primary mechanism for phreatomagmatic eruptions.
Answer: False
Explanation: Phreatomagmatic eruptions are primarily driven by the *thermal contraction* of magma upon direct contact with water, not thermal expansion.
There is a scientific consensus that phreatomagmatic eruptions are solely driven by the thermal contraction of magma.
Answer: False
Explanation: There is an ongoing scientific debate regarding the exact nature of phreatomagmatic eruptions, with some researchers suggesting that fuel-coolant reactions, in addition to thermal contraction, may be critical to their explosive nature.
Surtseyan eruptions are less explosive than ground-based Strombolian eruptions because water dampens the explosive force.
Answer: False
Explanation: Surtseyan eruptions are significantly *more* explosive than ground-based Strombolian eruptions precisely because of the violent interaction between magma and water, which enhances the explosive force.
A pyroclastic surge in a Surtseyan eruption is a high-altitude cloud of ash that forms above the main eruptive column.
Answer: False
Explanation: A pyroclastic surge (or base surge) in a Surtseyan eruption is a ground-hugging radial cloud that develops *alongside* the eruption column, not a high-altitude cloud above it.
Surtseyan eruptions typically form tall, conical stratovolcanoes over time.
Answer: False
Explanation: Surtseyan eruptions typically form maars (broad, low-relief craters) and tuff rings (circular structures from quenched lava), not tall, conical stratovolcanoes.
Submarine eruptions account for a small fraction, less than 25%, of the Earth's total volcanic eruptive volume.
Answer: False
Explanation: Submarine eruptions are estimated to account for approximately 75% of the Earth's total volcanic eruptive volume, particularly those occurring near mid-ocean ridges.
Pillow lava is a type of dense, blocky lava flow typically found on land after effusive eruptions.
Answer: False
Explanation: Pillow lava is the most common type of *underwater* lava flow, characterized by its unusual rounded shape, and is found in submarine volcanic settings, not typically on land.
Subglacial eruptions are common in tropical, low-altitude regions.
Answer: False
Explanation: Subglacial eruptions typically occur in areas of high latitude and high altitude, due to the presence of glaciers and ice sheets, not in tropical, low-altitude regions.
Subglacial eruptions primarily cause hazards through the release of highly toxic gases, with meltwater posing minimal risk.
Answer: False
Explanation: Subglacial eruptions primarily cause hazards through the generation of significant meltwater, which can lead to dangerous jökulhlaups (glacial outburst floods) and lahars (volcanic mudflows), rather than solely through toxic gas release.
Tuyas are formed exclusively by effusive lava flows on dry land, resulting in their flat-topped shape.
Answer: False
Explanation: Tuyas are formed by eruptions beneath ice, involving a complex sequence of pillow lava, hyaloclastite, and Surtseyan activity, followed by effusive lava flows, not exclusively by effusive lava flows on dry land.
Which mechanism primarily drives phreatomagmatic eruptions?
Answer: Thermal contraction from chilling upon contact with water.
Explanation: Phreatomagmatic eruptions are primarily driven by the thermal contraction of magma when it comes into direct contact with water, leading to violent interactions.
What is the primary mechanism driving phreatomagmatic eruptions?
Answer: Thermal contraction of magma upon direct contact with water.
Explanation: Phreatomagmatic eruptions are primarily driven by the thermal contraction of magma when it comes into direct contact with water, leading to violent interactions and fragmentation.
What is a Surtseyan eruption considered the 'wet' equivalent of?
Answer: Strombolian eruptions
Explanation: A Surtseyan eruption is considered the 'wet' equivalent of ground-based Strombolian eruptions, but it is significantly more explosive due to the interaction of magma with shallow water.
What geological structures are typically formed over time by Surtseyan eruptions?
Answer: Maars and tuff rings.
Explanation: Over time, Surtseyan eruptions typically form maars (broad, low-relief volcanic craters) and tuff rings (circular structures built from rapidly quenched lava).
What percentage of the total volcanic eruptive volume on Earth is estimated to be generated by submarine eruptions?
Answer: 75%
Explanation: An estimated 75% of the total volcanic eruptive volume on Earth is generated by submarine eruptions, particularly those occurring near mid-ocean ridges.
What is the most common type of underwater lava flow, known for its unusual rounded shape?
Answer: Pillow lava
Explanation: Pillow lava is the most common type of underwater lava flow, characterized by its distinctive rounded, pillow-like shapes, formed when lava erupts into water and cools rapidly.
In what geographical areas do subglacial eruptions typically occur?
Answer: Areas of high latitude and high altitude.
Explanation: Subglacial eruptions typically occur in areas of high latitude and high altitude, where glaciers and ice sheets are present, facilitating the interaction between lava and ice.
What dangerous phenomena can result from subglacial eruptions due to the interaction of meltwater and volcanic material?
Answer: Jökulhlaups (glacial outburst floods) and lahars.
Explanation: The interaction of meltwater and volcanic material during subglacial eruptions can lead to dangerous jökulhlaups (glacial outburst floods) and lahars (volcanic mudflows).
A single volcano is typically limited to one characteristic eruptive style throughout its active lifespan.
Answer: False
Explanation: Volcanoes are not limited to a single eruptive style and frequently exhibit a variety of different types, including both passive and explosive events, even within a single eruptive cycle.
Columbia University volcanologists found that the 1963 Irazú Volcano eruption was likely triggered by magma that took a nonstop route from the Earth's mantle to the surface over just a few months.
Answer: True
Explanation: Research by Columbia University volcanologists indicated that the magma for the 1963 Irazú Volcano eruption ascended rapidly from the Earth's mantle to the surface in a matter of months, challenging previous models of slower magma transport.
Before the 1990s, deep-sea volcanic eruptions were easily detected by land-based seismometers.
Answer: False
Explanation: Before the 1990s, deep-sea volcanic eruptions were largely undetected because land-based seismometers could not detect sea-based earthquakes below a magnitude of 4.
Glaciovolcanism is primarily studied for its role in current atmospheric gas composition, not as a climatic marker.
Answer: False
Explanation: Glaciovolcanism is primarily studied as an important climatic marker, providing insights into past ice distribution and historical climate conditions, rather than its role in current atmospheric gas composition.
Mount Vesuvius exhibited phreatic activity just before its catastrophic 79 AD Plinian eruption.
Answer: False
Explanation: Mount St. Helens exhibited phreatic activity prior to its catastrophic 1980 Plinian eruption. The provided information does not state that Mount Vesuvius had phreatic activity before its 79 AD eruption.
Mount Kerinci in Indonesia is known for almost annual effusive Hawaiian-type eruptions.
Answer: False
Explanation: Mount Kerinci in Indonesia is known for producing almost annual *phreatic* eruptions, not effusive Hawaiian-type eruptions.
What did Columbia University volcanologists discover about the magma ascent for the 1963 Irazú Volcano eruption?
Answer: Magma took a nonstop route from the Earth's mantle to the surface over just a few months.
Explanation: Columbia University volcanologists discovered that the magma for the 1963 Irazú Volcano eruption ascended rapidly from the Earth's mantle to the surface in a matter of months, a finding that revised previous understandings of magma transport.
How did advances in technology in the 1990s improve our understanding of deep-sea volcanic eruptions?
Answer: By making it possible to 'listen' to acoustic T-waves released by submarine earthquakes.
Explanation: Advances in hydrophone technology in the 1990s enabled scientists to 'listen' to acoustic T-waves released by submarine earthquakes, significantly improving the detection and understanding of deep-sea volcanic eruptions.
Which volcano exhibited phreatic activity just before its catastrophic Plinian eruption in 1980?
Answer: Mount St. Helens
Explanation: Mount St. Helens exhibited phreatic activity immediately prior to its catastrophic 1980 Plinian eruption.
What type of volcanic activity is Mount Kerinci in Indonesia known for almost annually?
Answer: Phreatic eruptions.
Explanation: Mount Kerinci in Indonesia is known for producing almost annual phreatic eruptions, which are steam-blast events without new magma.
What is the primary rock type produced by mid-ocean ridge volcanism?
Answer: Basaltic rock
Explanation: Mid-ocean ridge volcanism primarily produces basaltic rock, which forms from the decompression melting of mantle rock.