EAPS 106 exam 2 - EAPS 106 Exam 1 Study Guide (Completed) PDF

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EAPS 106 Exam 1 Study Guide (Completed)...

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EAPS 106, Geosciences in the Cinema, Fall 2018 Midterm Exam 2 Review You should know the following: How subduction zone earthquakes cause tsunamis  The uplifting of the seafloor from elastic rebound during a subduction earthquake  Stuck area ruptures in an earthquake causing a tsunami How tsunami and wind-blown waves differ  Tsunami waves can have similar heights to large wind-blown waves, but carry a much larger volume of water, have a much longer wavelength (distance from crest to crest), and travel much inland  Wind waves come and go without flooding higher areas  Tsunamis run quickly over the land as a wall of water  In tsunamis water flows straight  In wind waves water flows in a circle How the characteristics of a tsunami wave change as a function of water depth  Out at sea: o Long wavelengths (crest to crest) o Low wave heights o Great speed (jetliner speed)  Approaching shore: o Slow down (car driving through campus)  Which causes the back of the waves to catch up to the front o Reducing wavelength o Increasing wave height When water waves will generally break  Tsunami waves (like all water waves) break when the wave height is about equal to the water depth Which type of earthquake generally causes a tsunami  Subduction earthquakes generally cause a tsunami o Tectonic subduction on tectonic plate boundaries The dangers tsunamis pose when they come on shore  A tsunami wave can continue coming on shore for 20 minutes and reach many miles inland, destroying everything and everyone in its path How we know about past tsunamis  Dozens of Tsunami Stones along the coast of Japan warn residents not to build below them, some are more than 600 years old  Our own tsunami stones are written in sand deposits along the entire coast of the Pacific northwest o Soil, tsunami sand, peat (old soil), tsunami sand The various causes of tsunamis, which have the potential to be the biggest, and which region of the US they endanger  Causes: o Distant earthquakes o Local earthquakes o Landslides o Volcanic eruptions

o Asteroid impact  ^ size of tsunami in that order from largest to smallest  The United States east coast is vulnerable to tsunamis generated by underwater landslides in the Atlantic About how many total people have been killed by historic tsunamis  Several hundred thousand people have been killed by tsunamis  ~600,000 people The indicators that a tsunami wave may be approaching and how much time you have to escape  Significant seismic shaking near the shore o 20-40 minutes  Tide going out very far and very fast o 5-10 minutes  Tsunamis consist of 3-10 waves, and often the 2nd or 3rd wave is the largest – don’t go back to the shore until given the all clear or at least many hours have passed Why so many people died around the Indian ocean due to the 2004 tsunami  How the DART tsunami early warning system works  The DART early warning system can send out tsunami warnings in as little as 15 minutes after an earthquake, including path and size estimates  The key is the pressure sensor on the seafloor  Steps: o A sensor on the ocean floor measures water pressure o The measurements are sent by acoustic signal to a buoy on the surface o The transmitter buoy sends the signal further to a satellite o The signal is then sent to early warning stations on land How the Hawaiian Islands generate tsunamis  Underwater landslides on the islands of Hawaii have caused numerous tsunamis What caused the largest tsunami run-up (the height water reached on land) ever recorded  In 1958 a tsunami generated by an avalanche in Alaska caused the highest tsunami run-up ever recorded The settings where the different types of volcanism are found  On the Earth there are three settings were volcanism occurs: o Mid-ocean ridges o Subduction zones o Hot spots What the Ring of Fire refers to  The ring of fire refers to subduction zone volcanism that occurs everywhere that plates are subducted, causing a “ring of fire” around the Pacific Ocean Understand the cause of hotspot volcanism and why it leads to a chain of volcanoes  Hot spot volcanoes are caused by an age progression from one end to the other  The movement of the Pacific plate drags the head of the magma plume (magma under the surface) How and where hot rocks melt  The vast majority of the mantle is below its melting temperature

Magma (melted rocks) only occurs in very specific places and actually comprises only a very small percentage of mantle volumes  How: o Increased temperature o Decreased pressure as the rock rises o Addition of water (decreased melting temperature) What viscosity is a measure of  Viscosity is a measure of how easily a fluid flows How shield, stratovolcanoes, and cinder cones form  Shield: o These volcanoes have low viscous lava and broad topography  Stratovolcanoes: o Midsized volcanoes that form due to altering layers of pyroclastic flows (explosive) and lava flows (effusive)  Cinder cones: o Built when tephra (cooled lava fragments) are thrown out of a volcanic vent Know some basic facts about the Hawaiian Islands (how they formed, whether they are tall)  Hawaiian Island are shield volcanoes  The island of Hawaii is a huge shield volcano and is the tallest mountain on Earth as measured from its base (the seafloor) to its top What causes explosive eruptions and the factors that influence whether a volcano will explode  The shape of a volcano and the likelihood of it erupting explosively is dependent in part on the viscosity of its magma  Three main factors control whether a volcano will erupt explosively or effusively: o Amount of magma:  the more magma. The more dissolved gas o Amount of dissolved gas:  the more gas, the greater potential for pressure build up o Viscosity of magma:  Low viscosity magmas will flow through cracks to the surface, while sticky magmas will resist flow and allow great pressure to build The four main types of eruptions and their relative sizes  Hawaiian eruption o Smallest o 6,500 ft. o < 2 km  Strombolian eruption o 38,000 ft. o < 10 km  Vulcanian eruption o 65,600 ft. o < 20 km  Plinian eruption 

o Largest o 180,400 ft. o < 55 km About how many volcano-related deaths have occurred in the past 500 years  More than 250,000 people have been killed due to volcano-related deaths in the last 500 years The basic characteristics of the various volcanic hazards and which ones cause the most and least fatalities  Basic characteristics of volcanic hazards: o Unknown o Lightening o Seismicity o Flood o Debris avalanche o Gas o Lava o Tsunami o Indirect (famine, etc.) o Mudflow (indirect) o Mudflow (direct) o Pyroclastic flow/surge o Tephra  Pyroclastic flow/surge, Indirect (famine), tsunami, and direct mudflow cause the most fatalities Know the common precursors to a volcanic eruption and whether volcanic eruptions are predictable  Precursors: o Earthquake frequency increases o Harmonic tremors o Gas release (sulfur or carbon dioxide) o Rapid ground deformation (uplift or tilt) o Surface temperature increase  Volcanic eruptions can be predicted to within days, but these predictions are never straightforward Why the destruction of Pompeii in 79 AD is so interesting  2,000 people were killed  A description of the eruption was written down by Pliny the Younger  Pompeii was buried under more than 30 feet of ash and lost from history for 1500 years, but was preserved by the ash and dug out  The ash preserved the forms of the dead Why Pliny the Younger was famous for  Pliny the Younger is famous for writing down an unbelievable account of the eruptions of Mount Vesuvius and the destruction of Pompeii  “You could hear the shrieks of women, the wailing of infants, and the southing of men; some were calling their parents, others their children or their wives, trying to recognize

them by their voices. People bewailed their own fare or that of their relatives, and there were some who prayed for death in their terror of dying. Many besought the aid of the gods, but still more imagined there were no gods left, and that the universe was plunged into eternal darkness for evermore.” Understand what the Volcano Explosivity Index (VEI) scale is a measure of  The Volcano vity Index (VEI) measures the volume of ash and other rock to compare the sizes of different volcanos to each other Know why geysers erupt but hot springs do not  Geysers erupt because their hot water and pressure gets trapped under the surface and eventually the pressure gets too high and it must explode How we know Yellowstone is a hotspot  When the lava plume head hit the surface it erruped a giant flood basalt folowdd by a hotspot track to its present location beneath Yellowstone  We know that Yellowstone is a hot spot due to the pate motion and volcani trail that give us its timeline How calderas form  A caldera is a large circular depression formed when the surface collapses into an emptied magma chamber  Though associated with very large explosive eruptions, calderas are much bigger than an eruption crater The history, evidence for, and consequences of large, explosive eruptions at Yellowstone  Yellowstone has three calderas, indicating three very large eruptions in the past 2.1 million years (only two of the three were supereruptions) o Huckleberry Ridge Tuff and Island Park Caldera  Erupted 2,500 cubic kilmoeters of ash and pumice  2 million years ago o Mesa Falls Tuff and Henry’s Fork Caldera  Erupted 280 cubic kilometers of ash and pumice  1.3 million years ago o Lava creek Tuff and Yellowstone Caldera  Erupted 1,000 cubic kilometers of ash and pumice  600,000 years ago How the extent and activity of the magma chamber under Yellowstone is explored  Understand the global consequences of large explosive volcanic eruptions  Significant ash fallout  Large volcanic eruptions causing global cooling o Explosive eruptions emit large amounts of ash and SO2 o SO2 reacts with oxygen and water vapor to create sulfuric acid droplets o The ash and sulfuric acid droplets block sunlight, causing global cooling Why the Krakatoa, tambura, and toba eruptions were historically so significant  Tambura o “The monster creator” o In the cold Tambura summer of 1816, while together on holiday in Switzerland, Mary Shelley came up with Frankenstein and Lord Byron came up with Dracula  Krakatoa

o “The Scream” painting by Edvard Munch was influenced by sunsets in Norway altered by the 1887 Krakatoa eruption  Toba o The Toba caldera super eruption in Sumatra 74,000 years ago lead to global cooling that almost wiped out humanity o Observations from ice cores suggest that ash from Toba caused a 6-10-year cooling of 3 degrees Celsius which may have triggered the onset of a 1000 yearlong ice age o This ice age reduced the human population to only ~10,000 and maybe only 1000 mating pairs Understand the global consequences of giant flood basalts  Giant flood basalts may have been responsible for mass extinctions  Flood basalt ages often correspond with major extinction events in the world  Why? o Large amount of greenhouse gases led to global warming and acid rain o Lava flows with volumes 1000s of times those of ordinary eruptions...