What Controls Volcanic Eruptions?. Ch 12.2. Some eruptions are quiet…. Kilauea, Hawaii. Some eruptions are EXPLOSIVE!. Mt. Pinatubo. Montserrat. Mt. St. Helens. What Controls Volcanic Eruptions?. How much water vapor (a gas) and other gases are trapped in the erupting magma
What Controls Volcanic Eruptions?
Mt. St. Helens
Silica-rich magma is called granitic/rhyolitic magma
Results in explosive eruptions
Ex. Soufriere Hills in Montserrat
Characteristic of convergent plates
Silica-poor magma is called basaltic magma
Results in quiet eruptions
Characteristic of divergent plates
high in silica
high amount of trapped gases
lead to explosive type eruptions
Soufriere Hills volcano-active since 1995
At what type of boundary would granitic/rhyolitic magma form?
Sound heard 3,000 mi away!
13,000 x more powerful than nuclear blast at Hiroshima in WWII
Anak Krakatau (Child of Krakatau)
Mauna Kea, Hawaii
Mauna Loa, Hawaii
Common at divergent plate boundaries, mid-ocean ridges
Paricutin, Mexico (1943-1952, newest volcano in Western Hemisphere, 1000 killed)
Pu'u ka Pele on flank of Mauna Kea volcano, Hawaii
Mt. Fuji, Japan- one of the most photographed volcanoes in the world because of its near perfect symmetry
Ex. Mt. St. Helens
Volcanoes eject different types of material. This material is known as tephra or pyroclastic material.
There are 3 main types:
Ash-less than 2 mm in diameter
Lapilli/cinders-2mm-64 mm in diameter
Blocks orBombs-larger than 64mm
Mt Pinatubo, Philippines 1991