CH 6 Homework Questions
mass extinctions
According to the fossil record, what events have coincided with the approximate times when flood basalts were erupting?
at very shallow levels, such as within the volcano
At what depth do gas bubbles have the most effect on magma?
volcanic eruptions.
Changes in topography, water chemistry, and gas output all are used to help predict
The fluid cascade of lava.
Comparing these two photographs, which eruption has lower viscosity magma?
long fissures/dikes.
Flood basalt eruptions are fed by
All of these choices are correct.
Flood basalts influence life on Earth because
topography
Geologists use tiltmeters, GPS, and satellite radar maps to analyze the changes in __________ of a volcano.
All of these choices are correct.
Hazards associated with basaltic lava flows and eruptions are
hot spots
Large shield volcanoes are associated with which plate tectonic setting?
seismic shaking.
Magma rising through the crust fractures rocks, producing rhythmic, repeating
injected magma inflating the mountain.
Prior to an eruption, the surface of a volcano may rise centimeters to hundreds of meters as a result of
blocking of sunlight by volcanic ash and aerosols.
Reduced temperatures and growing seasons in Europe following the 1783 Laki eruption were primarily caused by
ejected fragments of vesicular lava.
Scoria cones are composed primarily of
All of these choices are correct.
Shield volcanoes commonly have
the low viscosity of basaltic magma allows it to flow downhill for long distances.
Shield volcanoes have low slopes primarily because
collapse of the roof of a magma chamber as magma erupts.
The main cause of caldera collapse is
composite volcano.
The most dangerous type of volcano is a
composite volcano
This relatively large, symmetrical volcano contains interlayered lava flow, pyroclastic deposits, and volcanic mudflows. What kind of volcano is it?
Shield volcano
This volcano is broad and low, and is composed of basaltic lava flows. What kind of volcano is it?
steep parts of the dome collapse and cause small pyroclastic flows.
Volcanic domes commonly are partially destroyed when
large amounts of rain and snowmelt mix with loose ash on steep slopes.
Volcanic mudflows (lahars) are common on composite volcanoes because
All of these choices are correct.
What are some factors that could allow flood basalts to have high-volume eruptions?
a rising mantle plume
What is the interpreted origin for magma that forms flood basalts?
lava dome
What type of eruption is shown in this photograph?
All of these choices are correct.
What types of rocks would be common in a composite volcano?
All these are used to monitor volcanoes.
Which of the following activities is NOT used to monitor volcanoes?
A pyroclastic flow forms when the gas flux cannot support the column.
Which of the following are differences between an eruption column and pyroclastic flow?
All these are true of felsic magmas.
Which of the following are true of felsic magmas?
Viscous magma prevents gas from escaping easily.
Which of the following are ways that viscosity affects gases in magma?
All of these choices are correct.
Which of the following commonly precede a volcanic eruption?
a volcano with a thick covering of snow or ice
Which of the following factors indicates a high risk for volcanic mudflows or lahars?
age of volcano
Which of the following is NOT a major controlling factor on volcanic eruption style?
Melting of snow caps dissolves large amounts of water into the magma.
Which of the following is NOT a reason why heat flow and gas output from a volcano tend to increase before eruptions?
age of the oldest volcanic layer present
Which of the following is NOT a way in which a volcano's history indicates the level of hazard it poses to nearby population centers?
They are fed from large interconnected composite volcanoes.
Which of the following is NOT true about flood basalts?
a scoria cone that erupts hot molten fragments on an unpopulated Pacific island
Which of the following is a hazard but not a risk, according to the textbook?
All of these choices are correct.
Which of the following is common in most calderas?
a volcano that contains andesite and welded tuffs
Which of the following is the best indicator that a volcano might be very dangerous?
Continent-continent convergent boundary with a high mountain range (Himalayas)
Which of the following plate boundaries is least likely to produce composite volcanoes?
A & B
Which of the following sites has volcanoes related to subduction? A is on an island arc, B is in the Andes, C is near Hawaii, D is along a mid-ocean ridge.
3
Which of the numbered features is a pyroclastic column?