Transcript Slide 1
Typically, where in the world do natural hazards occur? Hydrological Hazards •Hydrological hazards- (Flooding, drought). Flooding generally occurs on coastal plains or near rivers/lakes/streams. It happens when there is heavy rainfall that fills rivers or streams above their normal capacity, or if there are very high river or coastal tides that could cause levels to rise or surge. The excess rain water that gathers cannot be restrained by normal boundaries (such as a river embankment or man made levees) and follows the path of least resistance. Drought usually occurs where there is very hot, arid land. Mainly on the equator in places such as middle Africa and Northern Brazil. It happens when there in minimal rainfall and if the land is very dry it may not be able to absorb and therefore it evaporates back into the atmosphere. Atmospheric Hazards • Atmospheric hazards- (Cyclones, hurricanes, snow, fire, fog). Tornadoes occur in many areas around the world. However, no region experiences more tornadoes than the central United States. Besides this region, Brazil and portions of western Europe are perhaps especially at risk. In the British Isles, an average of 20 tornadoes per year are recorded. Canada receives approximately 13 tornadoes per year. In North America, most tornadoes occur in an area known as "Tornado Alley", which is the central Great Plains region of the United States. The states of Kansas and Oklahoma usually experience the most tornadoes per year. The Northern Hemisphere usually has about twice the number of tropical cyclones as the Southern Hemisphere (averaging 55 storms per year vs. 25 storms per year) Snow is common across most of North America, Europe, and Asia. Between the months of November and April, latitudes north of 40 degrees N receive an average of 25 inches (64 cm) of snow or greater. Wildland fires most commonly occur in southern grasslands and southern needleleaf forests, where vegetation is abundant, humidity is usually low, and temperatures are warm Geological Hazards • Geological hazards- (Landslides, sink holes) Slope failures can be triggered by weather events, geologic events, human modification of the landscape, or most commonly, some interaction of all of the above. Therefore, slope failures occur nearly everywhere slopes exist. Mountainous regions, hilly regions, and coastlines have the greatest occurrence of slope failures. Also, locations in active tectonic regions are prone to slope failures triggered by earthquakes or volcanic activity. Sinkholes form in karst landscapes, where water has dissolved underlying bedrock, typically limestone or gypsum. The southeastern United States is particularly prone to sinkhole formation; over 50% of the state of Kentucky is subject to these hazards. Along the highways of the Rocky Mountains and coastal mountain ranges of California, rockfalls cause transportation delays, vehicle damage, and road damage every year. Tectonic Hazards • Tectonic Hazards- (Earthquakes and volcanoes). Along the western edge of North America the oceanic crust is sliding under continental crust (a process known as subduction). In the world, three regions in particular are at significant risk of volcanic activity: The Pacific Rim (which outlines the Pacific Ocean) is also known as the "Ring of Fire" due to its extensive history of volcanic eruptions. Many countries around the Rim are at great risk of volcanic eruptions. In the east, these include Japan, the Philippines, Indonesia, New Guinea, New Zealand, and many of the South Pacific Islands. In South America, all west coast countries (Chile, Peru, Ecuador, Columbia) lie in the shadow of the explosive Andean Mountain Range volcanoes. The Mediterranean and Middle East regions including the countries of Italy, Greece, Turkey, Iran, Saudi Arabia, Yemen, and Pakistan have had a enormous amount of volcanic activity throughout history. Also the Great Rift Valley in eastern Africa has many volcanoes found in the countries of Ethiopia and Kenya. Tectonic Hazards ctn’d.... • In the last century, over 4600 earthquakes have been recorded along the western coast of North America. The western states, including California, Oregon, Washington, British Columbia, Yukon Territory, and Alaska are all prone to earthquakes. Baja California and western Mexico also have many earthquakes. The Pacific Rim (which outlines the Pacific Ocean) records more earthquakes than anywhere else on Earth. In the east, this includes the countries of Japan, the Philippines, Indonesia, New Guinea and New Zealand. In South America, all west coast countries (Chile, Peru, Ecuador, Columbia) are at risk. The Mediterranean and Middle East regions including the countries of Italy, Greece, Turkey, Iran, and Pakistan have been plagued by substantial numbers of earthquakes.