Eruption types Flashcards
What is magma?
melted rock
Traditionally and typically where is magma found?
under the Earth’s surface
what is magma primarily composed of?
silica rocks
- 45 to 75 percent of silicate minerals
magma is composed of ____ to ___ percent of silicate minerals
45 to 75
which minerals is magma composed of
silicate
temperatures of erupting lava range from..
800-1200 digress celsius
What is one of the most important properties of magma?
its viscosity
what is viscosity?
how thick a fluid is
viscosity is how _____ a fluid is
thick
fluids with high viscosity flow _____
slowly
fluids with low viscosity flow _____
easily
What two variables does a madams viscosity depend on?
temperature, silica content
higher temperature magma has a _____ viscosity
lower
the hotter the magma…
the more easily it flows
magma that has more silica (felsic) has a _____ viscosity
higher
if magma has high silica it…
flows more slowly
magma that has less silica (mafic) has a _____ viscosity
lower
less viscus magma lets gas escape more ______
easily
dissolved gas content of magma depends on….
viscosity
the nature of volcanic eruption depends on…
dissolved gas content
if you have a lot of dissolved gas you will get a more ________ eruption
explosive
more viscus magma…
holds more gas
less viscous magma are ______ explosive
less
different types of volcanoes form according to the different ______ that is being erupted at that point.
magma
low viscosity lava erupting creates…
Hawaiian type eruption
What do Hawaiian eruptions form?
- a type of volcano called shield volcanoes
- flood basalts
shield volcanoes form from…
Hawaiion eruptions
Hawaiian eruptions happened when there is…
low viscosity lava erupting
shield volcanoes are _____ and _____ volcanoes
large, broad
do shield volcanoes have explosive eruptions?
no
flood basalts are the ______ eruptions of lava on Earth
largest
What is the distance a flood basaltic eruption can exceed?
2000km
How long can the individual lava flow of a flood basalt flow?
10 plus years
Are flood basalts rare or common occurrences?
rare
Flood basalts provide evidence that…
the earth goes through periods of enhanced volcanic activity
major extinctions correspond with…
flood basalts
what is thought to cause flood basalts?
combination of continental rifting on top of a mantle plume that just brings abnormally hot material to the surface, and as that material rises to the surface the pressure drops and causes even more melting. huge gush of magma to the surface
Strombolian eruptions are created from _______ viscosity lava
intermediate
Strombolian eruptions form volcanoes called…
cinder cones
Cinder cones are _____ volcanoes made of loose volcanic rock
small
Plinian eruptions are composed of magma that has _____ viscosity
high
Plinian eruptions are _____ and _____
explosive, violent
Plinian eruptions form volcanoes called…
stratovolcanoes
- look like mountains, are tall, huge, have massive eruptions
What are the three types of volcanoes?
shield, cinder cone, stratovolcano
List the explosiveness of the types of explosions in order of least to most explosive.
- Hawaiian
- Strombolian
- Plinian
List the size of the types of volcanoes in order of largest to smallest
- shield
- stratovolcano
- cinder cone
What are four other features associated with volcanoes?
craters, calderas, geysers, fumaroles
what are craters?
bowl-shaped depression at volcanoes summit
What is a caldera?
larger depression from collapse due to emptying magma chamber
What is the only difference between calderas and craters?
calderas are much larger
How are geysers and fumaroles formed?
by hot water and gases from a nearby fuming magma chamber
what type of volcanoes do convergent boundaries tend to form?
stratovolcanoes (silica-rich magma)
where are volcanoes concentrated?
along plate tectonic boundaries.
where do shield volcanoes tend to form?
along divergent boundaries
