Download Volcanoes 2007

VOLCANOES
Lava & Magma
Lava vs. Magma…What’s the difference?
Lava- magma that flows into Earth’s surface;
the rock that forms when magma cools &
solidifies.
Magma- liquid rock produced under the
Earth’s surface.
Major Volcanic Zones
1.
Subduction Zone- one tectonic plate moves under another.
-deep trenches form
-island arcs form
2.
Mid-Ocean Ridges- plates pulling apart from one another.
-Produces the most magma from underwater volcanoes.
-Mid-Atlantic Ridge and Iceland are examples.
3.
Hot Spots- happen with the interior of plates.
-example = Hawaiian islands
-made by mantle plumes
Where volcanoes form
Hot Spots
Mid Ocean Ridges
Subduction Zones
Hot Spots
Types of Magma
1.
Mafic
-made up of magnesium and iron
-dark in color
-oceanic and continental crust
2.
Felsic
-made up of silicates
-lighter in color
-continental crust
Types of Eruptions
1.
Quiet Eruptions
-mafic magma
-oceanic volcanoes (Hawaii)
-low viscosity
2.
Explosive Eruptions
-felsic magma
-continental volcanoes
-high viscosity
-throw off large amounts of pyroclastic material
STRUCTURE
• Tephra
(pyroclastics) – ash
and rock ejected
from a volcano.
•Vent – conduit or
pathway for magma.
• Strata – layers of
rock.
• Magma chamber –
storage place for
magma.
LAVA
LAVA
Pahoehoe
AA
Pillow Lava
Tephra (pyroclastic material)
Volcanic Ash – the
small
stuff
Volcanic
Ash is
small,
but it is
the most
deadly.
Volcanic Blocks
Volcanic Bombs
Types of Volcanoes
1. Shield – Broad at the base, gently sloping sides, quiet
eruptions, largest volcanoes. (Exp- Hawaiian Islands.)
2. Cinder Cone – Explosive eruptions, very steep slopes,
only a few 100 meters high.
3. Composite of Stratovolcano – Explosive eruptions,
pyroclastic flows can be deadly, very large volcanoes.
(Exp- Mt. St. Helens, Mt. Pinatubo)
TYPES OF VOLCANOES
CINDER CONE
CINDER CONE
SHIELD VOLCANO
Mauna Kea, Hawaii
SHIELD
COMPOSITE VOLCANO
Mt. Fuji
Craters & Calderas
Crater- opening of the volcano where magma and or
pyroclastic material is released.
Caldera- when the magma chamber of a volcano
empties and collapses on itself.
CRATER
CRATER
CALDERA
Crater Lake in Oregon
Mt. Mazama
EXTRATERRESTRIAL
VOLCANOES
VOLCANOES FOUND ON MARS, IO (MOON OF
JUPITER), OUR OWN MOON
MARS – OLYMPUS MONS, 28 KM ABOVE THE
SURFACE, 600 KM ACROSS, CALDERA IS 70 KM
ACROSS.
IO – ACTIVE VOLCANOES ON SURFACE (FIRST
PLANETARY BODY TO HAVE ACTIVE VOLCANOES)
MOUNT ST.
HELENS
MT. ETNA
Predicting Volcanic Eruptions
-changes in earthquake activity around an
earthquake.
-increase in pressure of the surrounding rocks.
-temperature changes
-fracturing of rock
-sections of the volcano may bulge