GEOL 110 Natural Disasters Final Study Guide
GEOL 110 Natural Disasters Final Study Guide Geol 110
Long Beach State
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This 4 page Study Guide was uploaded by Astrea Presley on Tuesday May 3, 2016. The Study Guide belongs to Geol 110 at California State University Long Beach taught by Carla Weaver in Spring 2016. Since its upload, it has received 62 views. For similar materials see Natural Disasters in Geology at California State University Long Beach.
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Date Created: 05/03/16
GEOL 110-06 Final Study Guide Chapter 7 to 9 Chapter 7 - Tornadoes The Coriolis effect - The Earth rotates counterclockwise and this motion causes all ﬂuids (water AND air) in the northern hemisphere to be deﬂected to the right and to the left in the southern hemisphere. Atmospheric circulation (global winds) - warm aid rises toward the north from the equator and the cold air of the north goes south which then sinks when it reaches 30 degrees north or south of the equator. It is then affected by the Coriolis effect and causes trade winds, which blow from east to west and between 0 and 30 degrees of latitude. The westerlies blow west to east. El Nino - Normally occurring every 7-10 years, warm waters are pushed west by trade winds causing increased rainfall in the Paciﬁc. Dry conditions then prevail in the eastern part of the ocean. Trade winds get weaker or halt therefore the warm water goes back causing cooler water and droughts in the Paciﬁc. The Nor’easters - low atmospheric pressure and clockwise rotation due to the Coriolis Effect characterize a cyclonic storm. The Nor’easter is a tropical cyclonic storm that forms away from tropical regions and can bring intense snow and rainfall and normally occur in the winter which is why they are less intense than hurricanes. Mega-storm Sandy - Sandy is the second costliest hurricane in history. It started out as a category 2 which would have usually slowed down due to the warm Atlantic ocean but the ocean was 5 degrees colder than usual. A nor’easter storm combined with Sandy creating a mega-storm. The jet stream was unusual due to Greenland’s good weather which pushed Sandy ashore. Tornadoes: “A tornado is a rapidly rotating column of air that extends down from the base of a large thunderstorm” This rotation is not due to the Coriolis Effect but is due to winds meeting that travel at different altitudes and directions. “The meeting of winds traveling to opposite directions at different altitudes. The resulting shear force produces a horizontal rotation that is transformed into a vertical rotation by updrafts within the storms. This usually occurs in what is called a ‘supercell thunderstorm’” 70% of the worlds tornadoes occur in America, speciﬁcally tornado alley “which extends through the central states from Texas to South Dakota” This is because: Low-altitude, warm and moist air moves north from the Gulf of Mexico. Middle-altitude, cool and dry air ﬂows south from Canada or from the Rocky Mountains. High-altitude, cold jet stream winds blow east at high speed. Tornadoes travel at speeds of up to 62mph, but have rotating wind speeds of up to 318 mph; they have the highest wind speed of all weather-related natural processes, including hurricanes. Luckily, only 1% of tornadoes have wind velocities higher than 200 mph, but they are responsible for most of the deaths. The intensity of tornadoes are based on velocity of wind. The Fujita Scale assess damages based on wind speed. The Enhanced Fujita Scale replaced the prior in 2007 and considers varying degrees of damage. Chapter 8 - Flooding Every stream overﬂows every 2 1/2 years. Usually ﬂooding is caused by extensive rainfall or snow melt. When rain falls it can either inﬁltrate into the ground or run off into the surrounding area. Factors that affect inﬁltration: Type of soil Presence of vegetation Intensity of rainfall Topography Land use When land is untouched the trees in the forest slow down run off and inﬁltration. Deforestation causes reduction in inﬁltration and an increase in runoff which increases the chances of ﬂooding. “When 40% of an area is covered by urban surfaces (impervious covers) and its 40% is served by storm sewers, the probability of ﬂooding from a near-by river is 3 times greater than it was before urbanization took place.” Types of ﬂoods: Upstream - localized ﬂoods occurring in the upper portion that affect smaller areas like canyons and are caused by storms. They are deemed ﬂash ﬂoods because they often occur unexpectedly Downstream - regional ﬂoods occurring in the lower portion that affect larger areas and are caused by longterm storms. There is so much rainfall that inﬁltration decreases and runoff increases. Examples of rivers that usually have downstream ﬂoods are the Colorado and Mississippi “An alluvial fan is a fan-shaped accumulation of rocks transported by water that forms at the bottom of a canyon when the water slows down as it ﬂows from mountains onto a plain.” Flood hazards and how we respond: Physical barriers - levees, dams, ﬂood walls These barriers often fail so other solutions are being sought out Nonphysical barriers - regulation that limits building on ﬂoodplains Chapter 9 - Hurricanes Hurricanes are large tropical cyclones that include low-pressure systems that rotate counterclockwise in the Northern hemisphere and clockwise in the southern due to the Coriolis Effect. They often form in tropical regions between 5 and 25 degrees latitude. The absence of the Coriolis Effect at the equator make it impossible for them to form there. Tropical cyclones or typhoons occur in the western Paciﬁc ocean, Indian Ocean, and South Paciﬁc. Hurricanes occur in the eastern Paciﬁc, Caribbean sea and North Atlantic Ocean. Hurricanes occur mainly in the Summer months because the warm water transfers heat into the air which converts to winds and feeds the storm. These cyclones move across the Atlantic via trade winds from east to west. “During El Nino years, the number of hurricanes in the Atlantic Ocean actually decreases because the Trade Winds weaken and therefore are not strong enough to blow the storms forming by Africa across the ocean” The Coriolis Effect changes hurricane paths and causes a curvature to the right which increases with increasing distance away from the equator. Advanced prediction of hurricane paths and warning systems has decreased hurricane caused deaths although damage has increased exponentially because more people populate coastlines where houses are usually bigger and more expensive. Strong winds and storm surge (which creates ﬂooding) cause most of the damage in a hurricane. Barrier Islands are islands made of sand parallel to the coast. They are “basically sand dunes that used to be part of the mainland when the sea level was lower thousands of years ago, but became separated from it when the sea level rose.” Safﬁr - Simpson Scale - determines potential damage via the strength of a hurricane. The storm surge height, wind velocity and air pressure are all factors. These range from category 1 to category 5. Hurricane Katrina: New Orleans was built on the Mississippi River delta and has been subsiding for years. The result: the city is partially below sea level. Hurricane Katrina devastated this area because levees failed during the storm during which caused 80% of the city to ﬂood. Deadly hurricane and cyclones: The deadliest hurricane in the US was in 1900 in Galveston, TX. A category 4 hurricane killed over 8000 and washed over an inhabited barrier island.
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