Download Volcanoes

Volcanoes
A
mountain that forms when molten rock,
called magma is forced to the Earths
surface.
Nonexplosive Eruptions
Lava
is defined as magma that flows onto
the Earths surface.
Some lava may be sprayed into the air.
Low gas content.
Pose a greater threat to property than
human life.
Explosive Eruptions
Clouds
of hot debris and gases shoot out
from the volcano at supersonic speeds.
Molten rock is blown into millions of pieces
in the air.
Dust size particles may travel for years in
the upper atmosphere.
Volcanoes shrink after explosion due to the
used up magma in the magma chamber.
Definitions
Magma
chamber: under the volcano where
magma is stored.
Vents: holes in the crust where magma and gas
are released.
 Plug: mass of solid lava that blocks a volcano’s
vent.
Geothermal energy: power made from heat
within the Earth.
Geyser: fountain of hot water and steam erupting
from the ground in a volcanic area.
3 Types of Volcanoes
Cinder Cone
Made
up of piles of ash and cinders that collect around
the opening.
Steep sides and narrow base
Very explosive due to thick magma and lots of water
vapor trapped inside.
Located in South America.
Shield Cone
Forms
from easy flowing lava from cracks in the crust.
Large mountains with gentle slopes.
Not explosive, magma is thin with little gas.
Hawaiian Islands are shield volcanoes
Composite Cone
Combination
of a shield and cinder cone.
Eruptions can change drastically from easy
flowing lava to some of the most explosive and
destructive volcanoes.
Example: Mt. St. Helens
Magma
Water
saturated
If contains lots of water it is more likely to
explode.
Compare it to shaking a can of soda then
opening it up.
Water saturated magma is found along
subduction zones.
Example: Mt. St. Helens
Magma Continued
Silica
rich
Causes
magma to thicken up.
Vents plug up
Leads to more explosive eruptions.
Less silica equals to easier flowing and
thinner lava.
Types of Lava
1.Blocky
Lava
- Stiff
- Cannot travel far from the erupting vent.
- Forms a jumbled heap of sharp edged
rocks.
More Lava
2. Pahoehoe Lava
- Flows slowly
- Looks like dripping wax
- also looks like a glassy surface with rounded
wrinkles
And more Lava…
3. Aa Lava
- Hawaiian Lava
- has a jagged surface
- stiff lava that flows out quickly and forms a stiff crust
-Lava underneath continues to flow, thus tearing the above
crust and making it jagged
And more lava…
4. Pillow lava
- Forms when lava erupts underwater
- Forms rounded lumps
Pyroclastic material
Produced
when magma explodes from a
volcano and solidifies in the air.
Produced when existing rock is shattered
by eruptions.
3 types
Types of Pyroclastic Material
1.Volcanic
bomb
- Large blobs of magma that hardens in the air.
- Produced from volcanoes with high silica content
More Pyroclastic Material…
2. Lapilli
- Latin for Little stones
- Pebble size bits of magma that become
solid before hitting the ground.
More Pyroclastic Material…
3. Volcanic Ash
-Forms when gas in stiff magma expands
rapidly and the walls of the gas bubbles
explode into tiny glass like shards.
Volcanic Depressions
Craters
- the depressions that forms on the top of a
volcano as a result from an explosion or
collapse of material.
More Depressions…
Volcanic
Caldera
- Bigger than a crater, forms when
magma chamber that supplied material to
a volcanic eruption empties and its roof
collapses.
Hot Spot Volcanoes
Places
on Earth that are directly above columns
of rising magma called Mantle Plumes
Not located near plate boundaries
Mantle plumes stay in same spot while the
tectonic plate moves above it