Volcanoes
What are the 3 major types of
volcanoes?
• Shield
– Gentle sloping sides, slow moving/runny lava
• Composite
– Tall, steep sides. Very violent eruptions. Thick
sticky lava. Layers made of __________,
_____, and pyroclastic materials
• Cinder Cone
– Short, ______ sides. Layers made of ash.
– What do you think pyroclastic means?
LAVA DOME
A type of volcano often formed on or near
another active volcano. Magma rises just
under the crust and cools.
What is volcanism?
Any activity that includes the movement of
_________ toward or onto the ________
of the earth.
Because of high temperature and pressure
in the earth- pockets of magma form when
surrounding rock ______, as more rock
melts, the pocket grows
Predict what happens next.
Why does the magma come to the surface?
The magma is hotter, and less _______ than rock so it
rises to the surface through _______ in the rocksmelting more rock.
This occurs mostly at plate boundaries
Any magma that makes it to the surface is called ______the opening it comes through is called a ______.
The build up of material over the vent is a _______.
http://www.youtube.com/watch?v=mYekQtFLT2A
http://www.youtube.com/watch?v=ZZnvzSpNLAE&feature=related
What state do you think has the most volcanoes?
Volcanoes at subduction zones
What happens here? Draw a picture of what
you think happens.
Volcanoes at subduction zones
O-C plate boundaries:
Oceanic is pushed under the continental,
melting the plate.
Magma rises to the surface _________, the
crust buckles _______, trenches form at the
boundary.
O-O
Same as O-C, just under water. Volcanoes here
are called island ______volcanoes. Japan and
Alaska
Why does Oceanic plate subduct more often the
cont?
What happens at divergent boundaries?
What happens at divergent boundaries?
As plates move apart magma comes to the
surface making mid ocean _________
Most of the eruptions here goes unnoticed,
mountains and volcanoes are continuously
forming. They can be seen only on land in
___________.
Iceland is in part a __________.
Where is Iceland?
Hot Spots
Not all volcanoes are on __________.
Sometimes magma can rise to the surface in
the _____________ of a plate.
These volcanoes seem like they are
stationary, however, as the plate moves
over the hotspot new volcanoes are
formed, and old ones are __________
away.
http://www.youtube.com/watch?v=tfXGbzgGJ74&feature=related
Types of lava
Different types of ____________ make different
types of lava.
Mafic- oceanic crust- full of ________ and
magnesium- dark in color- small __________quiet eruptions
Felsic- continental crust- ________rich- light in
color- large crystals-violent eruptions
Pahoehoe (Pah-Hoy-Hoy)- slow moving- “______”
Aa (Ah Ah)- quick cooling- jagged chunks
Pillow lava- when lava flows onto the ocean floor
through ____________
Write 2 things you learned about volcanoes today.