Transcript Powerpoint

Volcanoes
By: Amy Axelrood
Formation and Eruptions of
Volcanoes
• Gas and buoyancy
pressure push magma
up against the earths
crust
• Weak parts in the
earth’s crust fracture
and crack and the
magma erupts out
• Eruptions can be
violent and explosive
or non-explosive
http://www.geology.sdsu.edu/how_volcanoes_work/index.html
Types of Volcanoes
• There are four types of volcanoes
-Shield Volcano
-Cinder Cone Volcano
-Composite Volcano
- Lava Domes
Shield Volcano
• Gently sloping
• Can be some of the
largest volcanoes
• Is formed when thin
layers of lava pour out of
a vent and harden on top
of previous layers
• Its profile looks like a
warriors shield
• Created the Hawaiian
Islands
• Mauna Loa
Cinder Cone Volcano
• Steep, cone shaped
hill or mountain
• Materials build up
around the edges to
create a cone shape
• They have violent
and explosive
eruptions
Composite Volcano
• Tall, cone shaped
mountains
• Layers of lava alternating
with layers of ash
• Some examples are Mt.
Fuji (left) and Mt. Saint
Helens (next slide)
• Wider base than Cinder
Cone
Mt. Saint Helens
Lava Domes
• Due to the
lava’s thick
density and
inability to flow
the lava clogs
the vent
• There is still
pressure on the
lava, but instead
of flowing it
domes up and
hardens
Location