Transcript File
Volcanic Energy What is a Volcano? Pyroclastic Flow Vent Pipe Lava Flow Magma Chamber A Volcano is a weak spot on the Earths Crust. Magma – Below Earths surface (w/gasses) Cools & forms rock. Lava – Above Earths surface (w/o gasses) Cools & forms rock. The World of Zits and Stretch Marks There are over 600 volcanoes. Most volcanoes are likely to be found along plate boundaries. Volcanoes & Plate Boundaries • Divergent & Convergent Plate Boundaries Briefly explain how volcanoes form at plate boundaries. Volcanoes & Plate Boundaries • Hot Spots Briefly explain how volcanoes form at hot spots. Types of Energy Associated with Volcanoes • Thermal Energy • Mechanical Energy • Light Energy – (Glow & least effective for change) • These energies combined change the earths surface How does it work? Ash, Gasses, etc. Overlying Rock Pressure Demo: Flask, boiling water Overlying Rock Pressure is Overcome by internal Pressure Gas Pressure The explosion of a volcano is similar to the soda water bubbling out of a warm bottle of soda pop. dissolved gases are trapped In magma under pressure. As magma rises, the gasses have less pressure and expand and form bubbles & puts pressure on crust blamo - eruption. When a volcano erupts, it unleashes a ton of energy. 2 Kinds of Eruptions • Quiet • Explosive – Dependant upon Silica content in the magma Quiet Eruptions • Low silica makes it flow easier as gasses bubble out gently. It oozes quietly from the vent and can flow for many kilometers. – Aa – Pahoehoe – Spatter Cone Explosive Eruptions • A volcano erupts explosively if its magma is high in silica. High silica content has more viscosity – from chemical bonds breaking and reforming, making it thick and sticky. Explosive Eruptions • High viscosity magma does not always flow out of the crater. Instead, it builds up in the volcanoes pipe, plugging it like a cork in a bottle. • Dissolved gases, including water vapor, cannot escape from the thick magma. – The trapped gases build up pressure until they explode. – The erupting gases and steam push the magma out of the volcano with incredible force. Volcanic Hazards Volcanic Hazards Quiet Eruptions • Quiet Eruptions: – Lava flows from vents, setting fire and burying everything in its path. – Covers large areas with a thick layer of lava. Volcanic Hazards Quiet Eruptions Fig. 7.23a Stephen Teachers, Please Marshak don’t mark your students tardy – we have a bus that’s running late. * Volcanic Hazards Explosive Eruptions • Explosive Eruption – Belches out: • hot clouds of deadly gases, ash, cinders & bombs. – Ash covers entire towns. • If wet, heavy ash causes roofs to collapse • If jets suck it in, the engine fails – Eruptions cause landslides and avalanches of mud, melted snow and rock. DVD: Dante’s Peak – moment at explosion. Mt. Saint Helens Mt. Saint Helens Mt. Saint Helens Mt. Saint Helens Mt. Saint Helens The Aftermath The Aftermath The Aftermath Rabaul Caldera on September 19, 1994 U.S. Clark Air Base, Philippines, about 25 km east of Mount Pinatubo Monitoring Volcanoes • Because volcanoes have a lot of energy, we can use instruments to detect that energy to determine when she’s gonna blow! – Tilt Meters – Seismometers Top 10 Signs it’s Gonna Blow Things we look for when we Monitor • • • • Bulging (M) Tilting (M) Increase in Earthquakes – (M) Increase in Temperature from underground water – (Th/Ht) • Out-gassing – (M) • Many other indicators Increase in Earthquake Activity Volcano Vocab Ash Rock, minerals and volcanic glass. Can travel thousands of kilometers away from the volcano Pyroclastic Flow Gases and rock traveling down from the volcano due to gravity. Temperatures can reach 1000° C and travel up to 700 km/hr Lahar Flow of mud and water. Often caused by volcanic eruptions that melt snow and glaciers. Can travel over 50 m/s, 140 meters thick and be hot or cold Aa High Viscosity lava flow Pahoehoe Low viscosity lava flow http://discoverykids.com/games/ volcano-explorer/ Lava Based Volcanic Landforms • Shield Volcanoes – Largest volcano – Low Silica: Low Viscosity – Lava flows gradually builds a wide, gently sloping mountain. • Thin layers of lava pour out of a vent and harden on top of previous layers. • i.e. Hawaii Lava Based Volcanic Landforms • Cinder Cones – Smallest type of Volcano – High Silica: High Viscosity • Produces ash, cinders and bombs. • Materials build up around the vent in a steep, cone shaped hill or small mountain. • i.e. Paricutin, Mexico Lava Based Volcanic Landforms • Composite Volcano – 2nd Largest – Mix of other two (Medium Silica) – Sometimes lava flows alternate with explosive eruptions of ash, cinder and bombs. – Magma is a mix of Shield & Cinder – Tall, cone shaped w/ alternate layers of ash and lava.. Lava Based Volcanic Landforms • Lava Plateau – Instead of forming mountains, some eruptions of lava form high, level areas. • Lava flows out of several long cracks in an area. The thin, runny lava travels far before cooling and solidifying. Magma Based Volcanic Landforms Volcanic Neck Dike Magma Based Volcanic Landforms Batholiths Geothermal Activity • Hot Springs • Geysers Yellowstone