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Presentation on theme: "Volcanoes."— Presentation transcript:

1 Volcanoes

2 Volcano A volcano is an opening in the Earth’s crust where lava comes out


4 Where to find volcanoes
Volcanoes can be found in 3 general locations Divergent Boundaries Subduction boundaries Hot Spots

5 Divergent Boundaries At divergent boundaries, volcanoes are created as the plates slide apart. Iceland is a good example.

6 Subduction Boundaries
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


8 Hot Spots 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.


10 Kinds of Volcanoes There are 3 kinds of volcanoes Shield Cone
Cinder Cone Composite Cone

11 Shield Cone Volcano Shield Cone volcanoes are not very tall and formed by layers of lava. Quiet Eruptions

12 Cinder Cone Steep Volcano with explosive eruptions.
Explosive eruptions caused by gas. Formed by layers of volcanic rock

13 Composite Cone Made of alternating layers of lava and rock
Alternates in explosive eruption and quiet eruptions AKA Stratocones

14 Volcanic lava 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

15 pahoehoe aa

16 Caldera vs. crater 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.

17 Caldera

18 Crater

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