Transcript Slide 1
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 (hot fragment of preexisting rocks that are blown from the vent of a volcano). 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 ***On the next few slides please draw each type of volcano in your notes*** 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 Washington State Mount St. Helens Before and After the May 18, 1980, Eruption Washington State 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 Pyroclastic Avalanche- Pahoehoe (Ropy) Lava Flow Fast Moving Pahoehoe Lava Slow-Moving Aa Flow Aa Lava Intrusive Activity Plutons- intrusive igneous rock bodies which are classified by shape, size, and their relationship to other surrounding rocks. -Batholiths-LARGEST plutons, irregularly shaped, coarsegrained igneous rocks. -Laccoliths-mushroom-shaped pluton with a round top and flat bottom. Relatively small -Sills-when magma intrudes parallel to rock layers -Dikes-a pluton that cuts across pre-existing rock layers *MANY PLUTONS ARE FORMED DUE TO MOUNTAIN-BUILDING PROCESSES Mt. Saint Helens Erupting Mount Saint Helens photographs 10-26-04 1980 Eruption Pompeii- Italy https://www.youtube.com/watch?v=QScagfQC5-w Santorini Greece Old Faithful- Yellowstone Sunset Crater – Flagstaff Arizona Kilauea Hawaii- Most active volcano Popocateptl- Mexico Mt Erebus Volcano- Antarctica One of the worlds most active volcanoes Please write down this link in your notes!!! http://www.cotf.edu/ete/modules/volcanoes/volcano.html