Volcanic Eruptions Flashcards
What are a direct consequence of plate tectonics and mantle convection?
Volcanoes
What are the products of a volcanic eruption?
- Volcanic gases
- Pyroclastic debris
- Lava flows
There are 5 volcanic settings: (MOCCC)
- Mid-ocean ridges—spreading axes
- Oceanic hot spots
- Convergent boundaries—subduction zones
- Continental rifts—incipient ocean basins.
- Continental hot spots and flood basalts
There are 3 types of lavas
Basaltic lavas are runny (low viscosity).
Rhyolite lavas are thick (high viscosity).
Andesite lavas are in between.
Basaltic (mafic) lava flows are (T, SiO2, viscosity)…
very hot, low silica, low viscosity.
Pahoehoe (Hawaiian) describes…
basalt with a glassy, ropy texture
A’a’ (Hawaiian) describes…
basalt that solidifies with a jagged, sharp, angular texture.
What are Cinder Cones? Also called?
Cinder cones ALSO KNOWN AS Scoria cones, the smallest type of volcano, are cone-shaped piles of ejected lapilli-sized fragments that have built up at the angle of repose around the vent.
This has the highest SiO2 content and is the most viscous lava.
Rhyolitic lava
Where are magma chambers located?
Upper crust
A bowl-shaped depression atop a volcano.
A Crater
Where do Flank Eruptions occur?
On the sides on volcanoes
What is a caldera? How do they form?
Much larger than a crater. Calderas form when a magma chamber empties and the volcano collapses into the evacuated space.
They are typified by steep sidewalls and flat floors.
A gigantic volcanic depression
A Caldera
An avalanche of hot ash, gas, and debris that develops from some silica-rich volcanic eruptions.
Pyroclastic Flows
Felsic magmas have more or less gas than mafic
magmas?
Felsic = more gas Mafic = less gas
Lahars
Water-rich debris flows carrying ash and large blocks
Eruption Predictions
- Ground Swelling
- Seismicity
- Outgassing increases
- Change in springs
Mount Tambora
“The year without sun” - 1815
The process that drives volcanoes comes from?
Earth’s efforts to release heat
Magma moves upward in the Earth because of?
Buoyancy
The degree of explosivity of an eruption is strongly dependent upon ?
- Magma viscosity 2. magma volatile content
The largest known explosive eruptions produced how much ash?
2500 km cubed
