Transcript Volcanoes
Volcanoes Volcano facts How many eruptions? 15,110 volcanoes in last 10,000 years The highest peak? 6,887 m, Ojos del Salado (Chile) The biggest eruption? 2,500 km3,Yellowstone, 2.2 Ma (USA) First volcanologist? 79 AD - Pliny the Younger Total deaths 238,000 (1600-1982) History The word Volcano is derived from the name of the ancient Roman island of Vulcano. The Romans believed that Vulcan, the god of Fire and the maker of weapons, used the volcano on that island to forge his weapons. Definition of a Volcano 1. An opening in the crust of the Earth from which magma and gases escape to the surface. 2. The mountain that is formed from volcanic processes. Volcano Classification Active- are either currently erupting or have erupted recently. Over 500 volcanoes are in this group. Dormant- are not currently erupting but are considered likely to do so. Mt. St Helens was dormant for 123 years before it erupted in 1980. Extinct- or dead volcanoes have not erupted in recent history and are not likely to erupt. Anatomy of a Volcano A volcano is a mountain formed of lava and/or pyroclastic material. A crater is the depression at the summit of a volcano or that which is produced by a meteorite impact. A conduit, or pipe, carries gas-rich magma to the surface. Anatomy of a Volcano Types of Volcanoes The three main volcanic types are shield volcanoes, cinder cones composite cones Shield Volcanoes Shield volcanoes are broad, gently sloping volcanoes built from fluid basaltic lavas. Cinder Cones Cinder cones are small volcanoes built primarily of pyroclastic material ejected from a single vent. Steep slope Small is size Occur in groups Cinder Cones Composite Cones Composite cones are volcanoes composed of both lava flows and pyroclastic material. Most are located in the Ring of Fire (Ex Mt. Rainer) Large in Size Most Violent Eruptions Composite Cones Mt. Rainer Mount St. Helens Before and After the May 18, 1980, Eruption Factors Affecting Eruptions Composition of the Magma Temperature of the Magma Dissolved Gasses Viscosity- is the measure of a material's resistance to flow. Temperature- hotter magma’s are less viscous Composition- Silica Content High Silica- high viscosity Low Silica – low viscosity There Are Three Major Volcanic Zones Subduction Zones Mid-oceanic ridges Hot spots There are Two Different Types of Lava Pahoehoe lava (resembles braids in ropes) Aa lava (rough, jagged blocks) Pyroclastic materials is the name given to particles produced in volcanic eruptions Pahoehoe (Ropy) Lava Flow Fast Moving Slow-Moving Aa Flow Mt. Saint Helens Erupting Mount Saint Helens photographs 10-26-04 1980 Eruption http://www.youtube.com/watch?v=njV9ski1gB4 http://www.youtube.com/watch?v=pGImksoOwtU&featur e=related http://www.youtube.com/watch?v=1Vn6kxfD3Ek&feature =related Pompeii- Italy Santorini Greece Old Faithful- Yellowstone Sunset Crater – Flagstaff Arizona Mt. Merapi Nov 1, 2010 Eyjafjallajokull- Iceland Kilauea Hawaii- Most active volcano Popocateptl- Mexico Mt Erebus Volcano- Antarctica One of the worlds most active volcanoes