GLG 112 Test 3 Pretest
Choose the order of the stream where you would expect a flood with the largest discharge.
4th order
Ash layers from the three most recent caldera-forming eruptions at Yellowstone (2.1, 1.3, and 0.64 million years ago) stretch:
?
Prior to an eruption, the surface of a volcano may rise centimeters to hundreds of meters as a result of:
?
What happens to a river as it flows through a delta and encounters the sea?
?
What event triggered the main eruption of Mount St. Helens May 1980?
?? A landslide removed rocks and released pressure on the magma.
What is a floodplain?
A broad strip of land built up by sedimentation on either side of a stream channel. Covered with water during a flood.
The eruption that occurred on Mount St. Helens was triggered by:
A huge landslide caused a lateral blast that knocked down trees and buildings.
What is a drainage divide?
A ridge or strip of high ground separating one drainage basin from another
All of the following are lines of evidence written by Plato that support the hypothesis that Santorini is the location of the lost city of Atlantis except:
An advanced civilization built Atlantis - likely the Minoans who lived on Santorini *Zeus, the God of sky and thunder, sent "lightening and thunder" onto the city* Atlantis was a "city built of concentric rings" - likely a nested caldera "Red, white, and black" rocks surrounded Atlantis - these colors may be volcanic rocks of Santorini
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?
Average time between eruptions **Age of the oldest volcanic layer present** Length of time since last eruption Abundance of felsic pyroclastic materials in its deposits
What is the term for small, shifting channels that carry water away from the main river channel and distribute it over the surface of the delta?
Distributaries
Which of the following commonly precede a volcanic eruption?
Increased gas flow from a volcano Steam eruptions from the volcanic crater Increased heat flow from the volcano
How is mafic lava able to travel great distances away from the vent from which it is erupted?
Lava tubes insulate and funnel the lava very far away from the vent.
The downfall of which ancient civilization in the Mediterranean closely followed the caldera-forming eruption at Santorini?
Minoan
An urban community developer redesigns a neighborhood so that the streets are narrower and more vegetation is planted. Also, the residents are now required to install rainwater catchment systems on their properties. What is the effect of this change on surface runoff?
Surface runoff will decrease
What does it mean when the amount of SO2 emitted from the vent of a composite cone or caldera quickly decreases?
The volcano has stopped degassing because of an obstruction at the vent (i.e. the gas is trapped in the magma)
formed where the Nile River encounters the Mediterranean Sea, is:
a delta
A delta forms when:
a river slows and deposits sediment as it enters a lake or sea
Which of the following acts to keep a rock solid (instead of melting)?
an increase in confining pressure
Hazards associated with basaltic lava flows and eruptions are:
burial of roads and neighborhoods by lava flows house fires Volcanic gases and methane explosions
What typically happens when tributaries join the main river?
channel size increases water velocity increases the amount of discharge increases total sediment load increases
This relatively large, symmetrical volcano contains interlayered lava flow, pyroclastic deposits, and volcanic mudflows. What kind of volcano is it?
composite cone
What is the main hazard of a shield volcano?
destruction by moderately fluid lava flows that can flow far from the volcano
The amount of water flowing through a channel over a given amount of time is called its:
discharge
This relatively small volcanic feature consists of solidified lava and some volcanic ash. What kind of volcano is it?
dome
Shield volcanoes commonly involve:
fluid lava flows
The force behind a river's flow is:
gravity
Which of the following is properly called a flood?
if water spreads out over the floodplain
Continental rifts have a diverse suite of igneous rocks associated with them because melting occurs:
in the mantle and in the crust
What happens to water velocity downstream? It generally:
increases
How does the addition of water cause melting?
it changes the location of the liquid-solid boundary
Volcanic mudflows (lahars) are common on composite volcanoes because:
large amounts of rain and snowmelt mix with loose ash on steep slopes
Which of the following typically decreases downstream in a river?
maximum sediment grain size
As magma is generated along a subduction zone:
minerals in the subducted plate release water, which lowers the melting temperature of the mantle material above
The cross-sectional area of the channel of a stream or river is calculated by:
multiplying the channel's width by its average depth
The volume of water flowing through any part of a river per unit time is calculated by:
multiplying the velocity by the cross-sectional area of the river
A stream or river that flows all year is referred to as:
perennial
What hazards are associated with ash clouds and ash fall?
roof collapse, jet engine failure, volcanic weather, contamination of surface water. NOT fire
Which of the following volcanoes is generally the largest?
shield
Yellowstone is still an active volcano. Which of these signs of volcanic activity has not recently occurred at Yellowstone?
small ash eruptions
A hydrograph shows:
the change in a river's discharge over time
Which of the following influences whether a flood occurs?
the height of levees the amount of discharge urbanization (replacing farms or natural land with buildings) the width of the channel
Where is the cut bank located?
the outside curve of a meandering stream
Which of the following is true of a 100-year flood?
the probability of a 100-year flood occurring on any given year is 1:100