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 Mafic -made up of magnesium and iron -dark in color -oceanic and continental crust Felsic -made up of silicates -lighter in color -continental crust
Types of Eruptions Quiet Eruptions -mafic magma -oceanic volcanoes (Hawaii) -low viscosity 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 The End!