Volcanoes
Where do we find volcanoes? Most of the 550 active volcanoes are found along the edges of the Earth's plates. More than half of them encircle the Pacific Ocean in the so-called Ring of Fire.
Parts of a volcano
What is a VOLCANO? An opening in the earth’s crust through which molten lava, ash and gases erupt that originate in the mantle. MAGMA is an underground pool of molten rock. When it comes to the surface of the Earth, it is called LAVA.
CRATER – roughly circular top of vent VENT – opening where magma flows out
Volcano Terms SILL – horizontal layer of magma that flows between the layers DIKE – vertical layer of magma that cuts through the layers
Shiprock, New Mexico—vent and dike of old volcano Devil’s Tower, Wyoming—old volcanic vent
Volcanic—dust, ash, cinders, and bombs Volcanic Dust—less than .25 mm Volcanic Ash—size of rice grains Volcanic—dust, ash, cinders, and bombs Cinders—size of golf balls Volcanic Bombs—few centimeters to meters
Lahar vs. Pyroclastic Flow Lahar—mudflow with rocks, other debris, and water
Pyroclastic Flow— fast moving current of extremely hot gas
Shield Volcano Broad volcano with gently sloping sides Gentle eruptions of lava Example: Mauna Loa, Hawaii Olympus Mons (Mars) – Largest in Solar System
Galapagos Islands Ecuador Mauna Loa Hawaii Rangitoto Island New Zealand
Cinder Cone Volcano Very steep sides. Violent eruptions. Usually not taller than 1000’. Most abundant Example: Paricutin, Mexico
1943--cinder cone erupted on a farm near Paricutin 1943--cinder cone erupted on a farm near Paricutin. It built up a cone to 1,200 feet covering 100 square miles over the course of nine years. Paricutin, Mexico SP Crater, Flagstaff, Arizona Cerra Negro, Nicaragua
Composite Volcano (Stratovolcano) Steep sides, symmetrical cones Built up through eruptions of lava flows, volcani ash, cinders, and bombs Examples: Mt. Hood, Mt. Rainier, Mt. St. Helens
Mount Fuji, Japan Mount Hood, Oregon Mount Rainier, Washington Mount Shasta, California
Mt. St Helens BEFORE 1980
Mt. St. Helens AFTER 1980