CH. 5: Volcanoes & Volcanic Hazards Flashcards
Effusive volcanoes are those with low viscosity lavas that are likely ____ in composition. A _____ volcano is usually effusive.
mafic / shield
The character of a lava flow depends on the viscosity of the lava erupted. _____ lava is less viscous than ____ lava.
basaltic / rhyolitic
Which of the following terms best describes this extrusive igneous feature?
pahoehoe lava
rhyolite lava:
tends to erupt explosively due to pressure buildup from the high viscosity of the lava
volatile rich magmas are generated by melting due to addition of volatiles. At what plate tectonic setting does this occur?
convergent subduction
A caldera forms by:
draining of a magma chamber beneath a volcano during an eruption
Which of these volcanic settings produced 70% of the Earth’s surface?
lavas erupted at mid-ocean ridges
Which of the following is false about hot spot volcanism?
hot spot volcanoes are always explosive
Mt. Vesuvius erupted in a very violent explosion in 79 CE and buried the residents of Pompeii in ash. On the basis on this information, which of the following would you LEAST expect to find at Vesuvius?
basaltic (mafic) lava
Which of the following is true about lahars:
all are true about lahars
can occur even if an eruption has not occurred recently
can carry away people/buildings/other structures
high density + fast flowing floods of water and tephra
What makes CO2 gas hazardous to humans?
all are true about CO2 gas
it is colorless and odorless
it is denser than air so it will not rise rapidly and can easily be breathed i without one’s knowledge of its presence
it can deprive the brain of oxygen and cause fainting and or death
Flood basalts typically originate from:
a mantle plume
In the Mastering Geology assignment this week we learned about Flood Basalts. One example was the Columbia River Flood Basalt Province. Which of the following are true about these flood basalts?
the relatively flat features of solidified flood basalts is indicative of the very low viscosity of the lava when it was erupted and emplaced
the flood basalts have fine grained texture that indicates relative fast extrusive cooling
thick layers of basalt indicate many repeated eruptions of multiple lava flows with the youngest flows at the top
True or False. Landslides can cause volcanic eruptions even in extinct volcanoes
False
Identify the FALSE statement about pyroclastic flow hazards
they can flow up to 100 km away from a volcano
Why are volcanic rocks often exposed at Earth’s surface as hills, ridges, and mountains surrounded by areas of lower elevation?
volcanic rocks are often more resistant to erosion than surrounding rock
What main hazard do lava flows pose to humans?
destruction of immovable property
The main difference between lavas that form pahoehoe texture and lavas that form aa texture is:
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?
west
In which of the following lava types would you expect to see the development of pahoehoe?
basalt
Continental rifts produce magma that is formed by ____ melting in the mantle with felsic magmas produced by _____
decompression / partial melting of continental crust
If you find a 500 meter depression atop a volcano, it is likely a:
crater
Match each of the following ocean features with their tectonic setting.
- seamounts
- island arcs
- mid ocean ridge
- hot spots
- subduction zone
- divergent plate boundary
Identify the FALSE statement about volcanic ash hazards
it is not hazardous if breathed in because the size of particles is too small
