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Download Ring of Fire – Around Pacific area, lots of volcanoes
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Transcript
Geo [Somewhat Colloquiallized] Term Sheet : Volcanoes/Dating PART 1+2 Ring of Fire – Around Pacific area, lots of volcanoes Not a lotta volcanoes in Africa/mainland Asia Magma generated by: Dropping pressure (rocks coming up quickly)/Added water Geothermal gradient – The gradual increase in heat as you go deeper into the earth Mantle is made of silly-putty-consistency slow-flowing rocks Mafic (Max): Basalt – Higher melting temperature, less viscous, most common lava for Earth Shield volcanoes – Shallow, very gentle slope MORB – Mid-Ocean Ridge Basalt – Stuff that erupts from nearly every mid-ocean ridge volcano on Earth Felsic (Max): Rhyolite – Retains shape really well Magma chambers generally have conduit leading down S Wave – Perpendicular – Transverse (up down up down) P Wave – Back and Forth – Longitudinal (back forth back forth) Ground Tilt – Used to determine magma stuff Sill – Rising magma, moves with layers Dike – Rising magma, moves across layers - Basaltic Lava Types - Aa – Cooler, thicker, like a pile of rocks Pahoehoe – higher temperature, runnier, like honey, ropy texture at end Cinder cone – Common , small, explosive central vents, like rock launched up, few hundred meters tall, like sand poured out of hand but with big rocks called cinders, basalt, big pile of debris Strato Volcano/Composite Cone – Classic volcano, silicate, Mt. St. Helens, get larger than cinder cones, layers of cinder/ash/lava, layered (hence “strato”), active for long periods of time, explosions make irregular surface, lots of small eruptions Caldera-Style SUPERVOLCANOOOO – Massive, form giant depressed valleys when their magma chamber collapses (calderas), thought to be responsible for a lot of the lesser extinctions on Earth Tuff – Gangsta way to spell “tough”, also compressed volcanic ash into fake rocks Domes – Dacitic magma forms on volcano, blob Tambora – “Year without a summer”, 1815-ish enormous eruption Krakatau – Smaller than Tambora but still frickin’ huge, 1883 Volcanic Explosivity Index (VEI) 1 2 3 4__________________________________________________________5 > 1 km^3 (Mt. St. Helens) 6 > 10 km^3 (Pinatubu, Krakatau) 7 > 100 km^3 (Tambora, Thera, Mt. Mazama, Long Valley) 8 > 1000 km^3 (Taba, Yellowstone) Plennian Eruptions – Large mushroom cloud Pyroclastic Flows – Fast, hot, deadly, air Airfall – Gets sorted as it falls. From the air. Nyur nyur nyur Lahar – Colossal mud flows formed because of tuff and ash mixing with dirt and making it less stable Jokulhaups – Giant floods that come from volcano erupting under a glacier Pyroclastic particles – Volcanic debris ranging from ash (smallest) to blocks (biggest) Volcanic Breccia – Solidified debris – angular chunks in finer grain background Varvs – Annual layers that form in some sedimentary rocks in the same manner as tree rings Carbon (14) Dating – Only works for relatively recent stuff because it decays so quickly, also doesn’t really work for stuff after 1940 due to atmospheric nuclear testing Half-Life – Average time when half of nuclei disappear (for Carbon 14 about 5,730 years) Dendrochronology –Dating using tree ring counting