Volcanic Eruptions Flashcards
Volcanoes are mostly found along
Convergent boundaries
three types of magma
basaltic, andesitic, rhyolitic
is the process where the early-formed minerals are denser (heavier) than the liquid (melt) and sink toward the magma chamber
Crystal Settling
occurs during the ascent of two chemically distinct magma bodies as the more buoyant mass overtakes the more slowly rising body
Magma mixing
Most magma that erupts on the Earth’s surface is __________ in
composition and has a temperature of ______________°C to __________°C.
basaltic, 1000°C to 1250°C
partial melting of the ultramafic rock __________ will yield a magma of basaltic composition.
peridotite
Basaltic magmas are generated at
subduction zones
are steep-sided mounds that were formed from viscous lava (rhyolitic lava); lava domes can act like a plug when it begins to solidify and thus allow pressure to build in the magma chamber and result in a more explosive eruption
lava dome
formed when lava eventually cools and solidifies into an igneous rock body
lava flow
formed when large volumes of basaltic lava will flow onto the surface along large fracture zones
Continental flood basalt
an accumulation of extrusive materials around a vent (sometimes a fault or fracture) through which lava, gas, or pyroclastics are ejected.
volcano
relatively small and is formed when lava is ejected into the air and cools into pyroclastic material called cinders, which then fall and accumulate around the vent
cinder cone volcano
also known as “stratovolcano”; are cone-shaped volcanoes with steep slopes consisting of alternating layers of pyroclastic material and lava flows
Composite cone volcano
a circular depression where lava and pyroclastic material is being ejected
crater
are exceptionally large landforms composed primarily of basaltic lava flows. It has a broad cross-sectional shape due to the low viscosity of basalt which can travel considerable distances from the vent and spread out over large areas
shield volcano
a circular depression that forms after an eruption when large volumes of magma are ejected from a shallow magma chamber, leaving it relatively empty and thus causing it to subside/collapse.
caldera
three classifications of volcanoes
Active Volcanoes
Potentially Active Volcanoes
Inactive Volcanoes
The ____________ caused by the overlying rocks gives the molten material within the magma chamber a tremendous amount of fluid pressure.
confining pressure
a zone of molten material where magma accumulates and occurs at a considerable depth.
magma chamber
As magma rises and encounters less confining pressure, it expands and pushes outwards on the surrounding rocks, thereby creating ________ and ________ and subsequent earthquakes.
fractures and faults
If the overlying rocks at some point are no longer capable of containing the fluid pressure, then significant amounts of magma can make its way to the surface, resulting in a __________________
volcanic eruption
Eruptions create pulverized rock that is ejected along with the lava
which is collectively known as
pyroclastic materials
The finest material, called __________, can travel hundreds, even
thousands, of miles before falling back to Earth’s surface.
volcanic ash
solidified lava and pulverized rock
Tephra
ways to classify pyroclastic deposits and rocks
- Grain Size
- Grain Size Mixture
- Components
It is a relative measure of the explosiveness of volcanic eruptions, and was devised by Chris Newhall of the United States Geological Survey and Stephen Self at the University of Hawaii in 1982.
Volcanic Explosivity Index (VEI)
most common hazard on an explosive volcanic eruption
pyroclastic material and hot gases
also called as debris avalanche, occurs whenever steep flanks of a volcano become unstable and results rapid downslope movement
of rocks, debris, and/or snow/ice.
Volcanic landslide
also called a lahar or debris flow, is a mixture of ash, rock, and
considerable amounts of liquid water.
Volcanic mudflow
volcanic gas is mainly composed of
water vapor (H2O)
carbon dioxide (CO2)
sulfur dioxide (SO2)
