a volcano is an opening in the earth’s crust where lava comes out
TRANSCRIPT
A volcano is an opening in the Earth’s crust where lava comes out
Volcanoes can be found in 3 general locations
1. Divergent Boundaries2. Subduction boundaries3. Hot Spots
At divergent boundaries, volcanoes are created as the plates slide apart. Iceland is a good example.
When one plate subducts under another, a volcano is created. A good example is Mt. Fuji in Japan, Mt. St Helens in Washington and Aleutian islands in Alaska
Hot Spots are volcanoes that form in the middle of a tectonic plate. Hawaii is an example. As the plate moves, the hot spot stays in the same place, so a chain of islands is often created.
There are 3 kinds of volcanoes1. Shield Cone2. Cinder Cone3. Composite Cone
Shield Cone volcanoes are not very tall and formed by layers of lava.
Quiet Eruptions
Steep Volcano with explosive eruptions.
Explosive eruptions caused by gas.
Formed by layers of volcanic rock
Made of alternating layers of lava and rock
Alternates in explosive eruption and quiet eruptions
AKA Stratocones
Mafic lava – dark, no gas, not explosive, thin
Felsic lava – light, lots of gas, explosive, thick
Pahoehoe – ropey cooled lava, usually from mafic lava
Aa – thick, blocky cooled lava from felsic lava
pahoehoe
aa
Vent – name of actual opening of volcano
Crater – surrounding area around vent. Caldera – a collapsed vent; after a
volcano explodes, a huge opening left over from explosion.