Module 2 Notes
Module 2 Notes Geoscience 115
Popular in Science Behind the News- The World Around Us
Popular in Geology
This 4 page Class Notes was uploaded by Hannah James on Sunday September 6, 2015. The Class Notes belongs to Geoscience 115 at University of Wisconsin - Madison taught by Philip Brown in Spring 2014. Since its upload, it has received 13 views. For similar materials see Science Behind the News- The World Around Us in Geology at University of Wisconsin - Madison.
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Date Created: 09/06/15
Volcanoes What is inside the Earth and where is it coming out 0 Volcanoes often alter the shape of Earth s surface 0 January 2014 Mt Sinabung in Sumatra Indonesia erupted killed 14 O 2011 Not many eruptions but ash clouds from remote volcanoes sometimes affected modern life I Puyehue in Chile had dust clouds that circled the globe in S hemisphere O 2010 Eruption of Eyj afj allajokull in Iceland erupted under snow and ice and created ash cloud that disrupted air traffic for weeks 0 Recent eruptions O 1996 Mt Pavlov in Anchorage Alaska came to life with earthquakes that stirred the underground magma I Steam plumes and an ash clouds followed lava fountains upward spray of lava caused by the pressure of magma below it and two lava ows were still active months later 0 The Smoking Mountain I Popocatepetl located in Mexico is continuously active today wish steamash eruptions earthquakes etc 0 Awoke in 1995 has been quietly active since I A catastrophic eruption would be dangerous for millions 0 Volcanoes show us that Earth is alive 0 Earth is tons of hot molten rock covered by layers of cool rock I Hot rock is trying to find its way to the surface hence volcanoes I Hot rock has lots of energy so it creates steam explosions etc 0 Volcanoes have peculiar distribution 0 Most are located around edge of the Pacific Ocean Ring of Fire I This area is where tectonic plates collide heavier ocean ones sink beneath crust ones so it s one big subduction zone I Origin of lava ow is often 100km below a subduction zone I Sinking ocean crust contains hydrous minerals contains either H20 or OH in its structure and water in the pores in the rock that is under lots of pressure 0 This hot highpressure water is released and ows through the hot rock in the upper mantle and lower crust partially melting it and making it now magma rise through the crust O The lower you go the hotter magma gets 0 The upper mantle is thought to be the source of magma columns that feed volcanoes O Magma gathers in the magma chamber a few km below the surface pressure in the chamber increases until eruption causes it to decrease I Upward ow of magma can take many forms depends on chemical composition of magma and local geology 0 Making predicting eruptions difficultcomplicated 0 Forecasting volcanic eruptions is an inexact science 0 0 Issue is simple false alarms created cryingwolf effect I Cause a refusal to evacuate making a fatal mistake Forecasting depends on data such as the chemical nature of gases emitted changes before an eruption the slope of the land re ects subsurface magma movement etc I Issue is not gaps in science but lack of moneyequipment and people to gather data between eruptions 0 This baseline data can help identify changes before eruptions 0 Volcanic landscapes show how they change the Earth 0 Calderas large circular depressions surrounded by steep cliffs form when magma chamber empties and the surface above it collapses larger than a crater Crater circular depression at the top of a volcano through which gases lava etc are extruded I Crater Lake National Park is actually a caldera Lahar occurs when volcanic ash meets ice snow or liquid water and produces a torrential mud ow I 1985 lahars triggered by melting glaciers in Nevada del Ruiz Colombia buried the town of Armero killed 25000 I 1992 Mt Pinatubo in the Philippines released lahars but warnings prevented many deaths I Can also occur after eruptions loose ash mobilized by rain Pyroclastic ows incandescent ash and gas that ow downhill rapidly I 1902 Mt Pelee erupted with a ow killing 29000 I Hot gases reduce friction and allow the fat motion 0 After ow cools and stops material cools and forms an ash ow tuff if deposited material is thick enough the pumice and glass shards compress and form rock called welded tuff Phreatic Explosions when volcanic heat makes steam that explodes into the air Shield Volcano a volcano with multiple vents where lava ows without exploding I Ex Mauna Loa in Hawaii I Extremely uncommon because they form over a hot spot weak place in Earth s crust where magma rises to the surface not a subduction zone O Seamounts underwater volcanoes that form over a midocean ridge or a hot spot I As Pacific Ocean plate passes over hot spots it causes a new volcano I As the plate drifts away volcano stops erupting and new ones are made 0 Pillow Lava Forms during a slow underwater lava ow I As outside of ow cools it becomes elastic and the structure in ates with hotter uid lava from the inside 0 Increased pressure causes the lava to break through the crust and form an adjacent or overlying mass another pillow 0 Is a sign that an area was underwater during the formation of volcanic rocks 0 Columnar Joints Form during the cooling of volcanic rock ow contracts while cooling and forms fractures that produce a polygonal sixsided pattern I Below the surface these joints for parallel columns of igneous rock 0 Hot SpringsGeysers often get energy from heat contained in recently formed igneous rock which can be associated with a still molten magma chamber I Ex Old Faithful 0 Geothermal Power Plants Electricity generating stations that get energy by tapping hot water in underground rocks commonly heated by magma I Often located along the Ring of Fire 0 Flood Basalts are as if Earth spring a giant leak O Basalt is a common igneous rock that forms quick owing lava all the sea oors in the world are underlain by basalt 0 Flood basalts arise when lava oozed from a fissure in the Earth and ooded the landscape basalt makes the lava ow fast and far up to lOOkm per hour I This lack of viscosity thickness allows it to form these massive land provinces 0 Are interesting because past ones correlate with periodic extinctions in the fossil record I Evidence for these oods causing extinctions are mixed 0 EX one occurred when dinosaurs were wiped out but there is also strong evidence for a cometmeteor around that time 0 This process is occurring right now MidAtlantic Ridge 0 California has many volcanic effects to worry about 0 Long Valley Caldera has seen recent activity magma chamber is filling O Mammoth Mountain I Massive output of C02 which indicates resurgent magma 0 Largest Eruption in History 0 Aug 26th and 27th 1883 Krakatau in Southeast Asia erupted and sounded like a cannon up to 600 km away could be detected 4500 km away I Lofted 20 cubic km of rock into the ATM smoke and ash column 26 km above Earth s surface caused tsunamis that killed 36000 I Obliterated 23 of the 11 km island of Krakatau and darkened the sky for dozens of km around I Located on a subduction zone allowing for the power of the explosion 10000 times that of the Hiroshima bomb 0 Allowed scientists to observe new island colonization after the eruption I Species could get there by air passive transport oating sea oating or animal hitchhiker 0 Prof Ian Thornton wrote a book and talks about the colonization 0 Paricutin 1943 Central Mexico 0 Able to witness the building of the volcano from the ground up
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