GEO - Week 5 Notes

GEO - Week 5 Notes Volcanoes - Volcanoes are the structure in the earth ’ s crust containing an opening at the end of a central vent or pipe through which magma rises from the asthenosphere and upper mantle - Magma rises and collects in a magma chamber deep below the volcano until conditions are right for an eruption - If you have granite that is richer in tetrahedra, some chains are longer. Thew flow a considerable distance before they solidify. - There are more than 600 active volcanoes in the world - Eyjafjallajokull Volcano in Iceland erupted producing ash clouds that rose to 10,660m, closing airlines for 5 days and cancelling more than 100,000 flights - Volcanoes occur in the Pacific Ocean in what is called the “Ring of Fire” - Batholith - When magma solidifies and causes a big mountain - Laccolith - When magma solidifies and causes a small mountain - Result of plate tectonic activities Settings for Volcanic Activity 1. Along Subduction Boundaries at continental plate - oceanic plate convergence (Mount St. Helens, Kliuchevskoi, Siberia) or oceanic plate - oceanic plate convergence (The Philippines; Japan) 2. Along Seafloor Spreading Centres on the ocean floor (Iceland, on the Mid-Atlantic Ridge; off the coast of British Columbia, Oregon and Washington) and along areas of rifting on continental plates (the rift zone in East Africa) 3. At Hot Spots , where individual plumes of magma rise to the crust (Hawaii; Yellowstone National Park; Nazko region in central B.C) Two Types of Basaltic Lava: AA Lava: They create sharp spiky edges and form a thick skin over the surface of a slowing lava flow, cracking and breaking as it cools and solidifies. Pahoehoe: As lava flows out and begins to have contact with air, it twists and turns or curls into a cool shape forming patterns when the magma solidifies. It has lower viscosity than AA 1. Stratovolcanoes (Eg Mountain Rainier) - Spews Felsic lava and clouds of hot white gas - Composite volcanoes - they have erupted over the last years and the mountain is characterized by the deposition of different layers - It is symmetrical in shape - It is cone shaped - indicative of release of granite magma. Its very sticky so it doesn’t travel very far before solidifying - Very violent when it goes off - the conduit is often blocked and you have large accumulation of gasses, high pressure is created, should there be a little outlet, the mountain would just explode (many km of land could be covered in ash)