Unformatted text preview: National Parks formed by National Parks formed by Volcanic Activity (part 1)
Mount St. Helens National Volcanic Monument Crater Lake National Park Extrusive igneous rocks Different chemistry Volcanism Volcanism High Silica ~70% Rhyolite Moderate Silica ~60% Andesite Low Silica ~50% Basalt Chemistry controls viscosity Rhyolitic – very viscous Basaltic – very runny Lava Flows Volcanic Rocks Volcanic Rocks Aa Pahoehoe Pyroclastic material (based on size) Ash Lapilli Blocks Tuff Pumice and Scoria Types of Volcanoes Types of Volcanoes Shield Volcano Composite cone Volcanic dome Cinder cone Divergent plate boundaries Location of Volcanoes Location of Volcanoes Mid ocean ridges Continental rift zone Convergent plate boundaries OceanicOceanic Crust OceanicContinental Crust Hot spots Mount St. Helens Mount St. Helens Vital Statistics Southwest Washington 110,000 acres 170 square miles History History 6,5003,500 years ago evidence of NA 3,500 years ago eruption 1,500 years ago Numerous tribes 1792 British Royal Navy 1800 eruption Early 1800 Brit & US exploration History History 180506 Lewis & Clark 18311851 numerous small eruptions 18511980 inactive 18901910 mining 1982 Established by President Reagan as “Mount St. Helens National Volcanic Monument” Managed by the US Forest Service Geologic Features Geologic Features The Volcano & Mass Movements Stratovolcanic cone 18 MAY 1980 Earthquake Debris avalanche from collapse of dome Geologic Features Geologic Features The Volcano & Mass Movements Lateral blast Ash Eruption & Fallout Pyroclastic Flow New Crater Mud Flows Geologic History Geologic History Eocene 6040 mya flat coastal lowland, sandstone, shale, coal 40 mya coastal plain sinks, volcanic islands form Volcanic rocks and sedimentary rocks 30 mya uplift 25 mya fissure basalts 10 mya erosion to low hills 1 mya Mt Rainier and other vol mts begin to form, glaciation Activity since 1980 Activity since 1980 19801986 Continued activity, lava domes &small eruptions Winters of 1989 & 1990 ash eruptions 19902004 relatively quiet 2004 new lava dome March 2005 minor eruption 20052008 minor ejections of steam Crater Lake National Park Crater Lake National Park Vital Vital Statistics Southwest Oregon 160,000 acres 290 square miles Human History Human History Klamath tribe Mid 1800’s prospectors & soldiers 1883 Scientific Studies 1885 drive to NP status begins 1902 NP signed by TR Geologic Features Geologic Features Caldera of Stratovolcano Remnants of Mt. Mazama Igneous Dikes Cinder cones Glaciation Geologic History Geologic History Early history similar to other Cascades Volcanoes Mt. Mazama built starting 1 to 2 mya Glaciation during this construction ~7000 years ago eruption Between 6000 and 1000 ya creation of cinder cones ...
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- Spring '10
- Volcano, Helens National Volcanic, Geologic History Geologic, Dikes Cinder cones Glaciation, National Volcanic Monument, History Geologic History