2. How do volcanoes work?
• Magma is forced onto
Earth’s surface.
• It dries and hardens, this
happens many times over
thousands of years.
• Eventually a mountain
called a volcano is formed.
3.
4. Parts of a Volcano
• Most volcanoes share a
specific set of features.
• The magma that feeds the
eruptions pools deep
underground in a structure
called a magma
chamber.
• At Earth’s surface, lava is
released through openings
called vents.
• Flowing lava in the interior
travels through long, pipelike
structures known as lava
tubes.
5. Where do most volcanoes occur?
• Volcanoes occur at
both divergent and
convergent
boundaries and also
at hot spots.
7. Types of volcanoes
• Shield volcano: usually form at hot spots,
from non explosive eruptions
• Cinder cone volcano: form from explosive
eruptions, very steep.
• Composite volcano: form from both
explosive and non explosive eruptions.
8. Shield volcano
• Form from many layers of “runny” lava.
• Very wide, not to steep.
• Biggest type of volcanoes
• Tallest mountain in the world is Mauna Kea
(measures from sea floor to top)
• non explosive eruptions
10. Cinder cone volcano
• Smallest type of volcano
• Most common
• Made from pyroclastic material (material
shot out of a volcano)
• Form a large crater
• Explosive!
12. Composite volcano:
• Eruptions alternate between explosive and
non-explosive.
• Sometimes they have runny lava layers,
other times the have pyroclastic materials
form layers.
• Have a wide base and steep sides.
• Have a crater
• Mount Fuji
14. 2 Types of eruptions
• Explosive: volcanoes
that build enough
pressure to blow its
top, sending
pyroclastic material
into the air.
• Non explosive: Build
only enough pressure
to allow lava to run
down its sides.
15. Non explosive eruption
• Mafic: refers to rocks and magma rich in
iron and magnesium.
• This type of lava that is very runny.
• As magma nears the surface there is little
pressure, causing gasses escape easily.
• Magma low in Silica have quiet eruptions
16. Explosive eruptions
• Felsic: means magma with high silica and
feldspar content.
• Felsic magma traps water and gas
bubbles, which leads to lots of pressure.
• Silica acts like a cork
• Explosive eruptions are caused by a build
up of high pressure.
• Convergent zones contain lots of water,
therefore have explosive eruptions.
17. Pyroclastic materials
• Material that is thrown into the air during
an explosion.
• Volcanic bombs: large blobs of magma
that harden in the air.
• Lapilli: pebble size rocks
• Volcanic ash: tiny powder like material
18.
19. Four types of lava
• Aa: lava that is thick and sharp
• Pahoehoe: lava that forms thin crust and
wrinkles
• Pillow lava: lava that erupts under water,
has a round shape
• Blocky lava: cooler, lava that does not
travel far from eruption, jagged when it
dries.
