Geology 101 Chapter 5 and HW 5: Volcanoes
Which of the following indicates that a volcanic eruption could be imminent?
A change in the composition of gasses being released
Which of the following objects has a size similar to that of lapilli?
A marble (15 mm)
Which of the following is a feature of an aa flow?
Aa flows have sharp, jagged edges.
What is the difference between aa lava and pahoehoe lava?
Aa lava has a prickly texture; pahoehoe has a smooth, ropy texture.
Which of the following would decrease the viscosity of magma?
An increase in temperature
In order to cover such large expanses of seafloor, shield volcanoes erupt ________ lava.
Basaltic
Which of the following lavas make up 90% of the total volume of lava on Earth?
Basaltic
Which one of the following statements is NOT true about andesite and basalt?
Basaltic lava is thicker than andesitic lava.
What is one way that cinder cones differ from composite and shield volcanoes?
Cinder cones are smaller than composite and shield volcanoes.
Which of the following is the volcanic feature in which magma rises through before it is released at the surface?
Conduit
In general, why does Earth's crust sit on top of the mantle?
Earth's crust is less dense than the mantle.
Most cinder cones have eruptive phases that last for centuries. T or F
False
The more silica in magma, the lower the viscosity. T or F
False
What is the driving force behind pyroclastic flows?
Gravity
How are felsic magmas formed?
Heat from the mantle melts part of the lower crust.
Which of the following volcanic materials flows out of a volcanic vent?
Lava
Which of the following scenarios best describes how the Hawaiian Islands formed in the Pacific Ocean?
Magma generated from a hot spot burned through the overlying plate to create volcanoes.
Which of Hawaii's five volcanoes are still considered to be active?
Mauna Loa Kilauea
Volcanic ash is best described as which of the following?
Microscopic pieces of rock ejected by a volcano
The Ring of Fire is a narrow zone of composite cone volcanoes rimming the ________ Ocean.
Pacific
How do mafic volcanic rocks get to Earth's surface?
Pressure from overlying crust forces mantle magmas through cracks to Earth's surface. These magmas erupt out of volcanoes, cool, and solidify into rock.
________ is/are pulverized rock, lava fragments, and ash erupted from a volcano.
Pyroclastic materials
Lavas erupting from composite cones are generally ________-rich, making them very viscous.
Silica
Which type of volcanic hazard can decrease global temperatures?
Volcanic ash
Fumaroles
a flank vent that emits gases
Parasitic cones
a flank vent that emits lava and pyroclastic material
Crater
a funnel-shaped depression at the summit of most volcanic cones, generally less than 1 km in diameter
Caldera
a volcanic crater that has a diameter of >1 kilometer and is produced by a collapse following a massive eruption
In general, when will melted rock in the mantle rise?
almost always
In addition to viscosity, which of the following parameters has an influence on whether a volcanic eruption will be effusive or violent?
amount of gas in the magma
At which type of tectonic setting would you expect the development of composite volcanoes?
an oceanic plate subducted beneath a continental plate
In which of the following lava types would you expect to see the development of pahoehoe?
basaltic
Which of the following types of lava will most likely lead to a volcanic eruption of an effusive nature?
basaltic
What do we call pyroclastic material, ejected during a volcanic eruption, composed of incandescent lava that is greater than 64 millimeters (2.5 inches) in diameter?
bombs
Which of the following volcanic types typically produces small, steep-sided structures composed of pyroclastic material?
cinder cones
What is piled up along the cone of SP Crater that causes it to be so steep?
cinders
Which of the following volcanic forms best describes large, nearly symmetrical structures composed of interbedded lavas and pyroclastic material primarily deposited from a central vent?
composite volcanoes
What drives melting at divergent boundaries?
decompression melting
What type of boundary is present along the eastern boundary of the North American plate?
divergent oceanic-oceanic
Which materials in Hawaii's lava help to keep it fluid for longer at the surface (as opposed to cooling and solidifying quickly), thus allowing extensive lava flows to develop?
iron magnesium
What do we call mudflows produced by the melting of snow and glaciers on composite volcanoes?
lahars
At which of the following tectonic settings would you expect to find volcanoes producing significant amounts of very fluid, high-temperature lavas?
mantle plumes
At which type of tectonic setting would you expect the development of shield volcanoes?
mantle plumes
At what tectonic setting is Hawaii located?
oceanic hot spot
A hot spot that occurs in oceanic crust is likely to produce which of the following types of eruptions?
quiet and effusive
In which of the following lava types would you expect to find the greatest percentage of gases?
rhyolitic
In which of the following types of lavas would you expect to find the greatest production of pyroclastic material?
rhyolitic
Which of the following types of magma has the highest viscosity?
rhyolitic
At which of the following tectonic settings would you expect to find volcanoes producing the highest volumes of pyroclastic material?
subduction of an oceanic plate under a continental plate
Which of the following has the single most immediate effect on lava's ability to solidify?
temperature
The volcanic islands in the above figure were created as the tectonic plate passed over a hot spot in the mantle. Based on the ages of the volcanic islands, in what direction was the tectonic plate moving toward?
toward the west
Which of the following tectonic settings does NOT produce volcanism?
transform boundary
What causes vesicles to form in lava?
trapped gas bubbles
The subduction of oceanic crust under continental crust predominantly produces which of the following types of volcanic eruption?
violent and explosive
What type of volcanism characterizes the ring of fire?
volcanism caused by convergent oceanic-continental boundaries volcanism caused by convergent oceanic-oceanic boundaries
Which of the following gases is most abundant in basaltic lavas?
water vapor
When will magma rise to Earth's surface?
when the magma is less dense than adjacent rock
