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The Earth's Weather System and Disasters
Transcript of The Earth's Weather System and Disasters
(Dhan Dhan Dhan) Tornadoes
(Round and round we go) Although tornadoes occur in many parts of the world, these destructive forces of nature are usually found in the United States. East of the Rocky Mountains during the spring and summer months. In an average year, 800 tornadoes are reported nationwide, resulting in 80 deaths and over 1,500 injuries. A tornado is known as a violently rotating column of air extending from a thunderstorm to the ground. The most violent tornadoes are capable of tremendous destruction with wind speeds of 250 mph or more. Damage paths can be in excess of one mile wide and 50 miles long. Tsunamis
(Let's do the wave) A tsunami is a series of ocean waves that sends surges of water, sometimes reaching heights of over 100 feet (30.5 meters), onto land. These walls of water can cause widespread destruction when they crash ashore.These awe-inspiring waves are typically caused by large, undersea earthquakes at tectonic plate boundaries. When the ocean floor at a plate boundary rises or falls suddenly it displaces the water above it and launches the rolling waves that will become a tsunami.Most tsunamis, about 80 percent, happen within the Pacific Ocean’s “Ring of Fire,” a geologically active area where tectonic shifts make volcanoes and earthquakes common.Tsunamis may also be caused by underwater landslides or volcanic eruptions. In deep ocean, tsunami waves may appear only a foot or so high. But as they approach shoreline and enter shallower water they slow down and begin to grow in energy and height. The tops of the waves move faster than their bottoms do, which causes them to rise precipitously. Earthqakes Earthquakes, also called temblors, can be so tremendously destructive, it’s hard to imagine they occur by the thousands every day around the world, usually in the form of small tremors.Some 80 percent of all the planet's earthquakes occur along the rim of the Pacific Ocean, called the "Ring of Fire" because of the preponderance of volcanic activity there as well. Most earthquakes occur at fault zones, where tectonic platesgiant rock slabs that make up the Earth's upper layercollide or slide against each other. These impacts are usually gradual and unnoticeable on the surface; however, immense stress can build up between plates. When this stress is released quickly, it sends massive vibrations, called seismic waves, often hundreds of miles through the rock and up to the surface. Other quakes can occur far from faults zones when plates are stretched or squeezed.Scientists assign a magnitude rating to earthquakes based on the strength and duration of their seismic waves. A quake measuring 3 to 5 is considered minor or light; 5 to 7 is moderate to strong; 7 to 8 is major; and 8 or more is great.On average, a magnitude 8 quake strikes somewhere every year and some 10,000 people die in earthquakes annually. Collapsing buildings claim by far the majority of lives, but the destruction is often compounded by mud slides, fires, floods, or tsunamis. Smaller temblors that usually occur in the days following a large earthquake can complicate rescue efforts and cause further death and destruction. Hurricanes
(I think we're going in circles) Hurricanes are giant, spiraling tropical storms that can pack wind speeds of over 160 miles (257 kilometers) an hour and unleash more than 2.4 trillion gallons (9 trillion liters) of rain a day. These same tropical storms are known as cyclones in the northern Indian Ocean and Bay of Bengal, and as typhoons in the western Pacific Ocean.The Atlantic Ocean’s hurricane season peaks from mid-August to late October and averages five to six hurricanes per year. When a storm’s sustained wind speeds reach 74 miles (119 kilometers) an hour it becomes a hurricane and earns a category rating of 1 to 5 on the Saffir-Simpson scale. Volcanoes Volcanoes are awesome manifestations of the fiery power contained deep within the Earth. These formations are essentially vents on the Earth's surface where molten rock, debris, and gases from the planet's interior are emitted.When thick magma and large amounts of gas build up under the surface, eruptions can be explosive, expelling lava, rocks and ash into the air. Less gas and more viscous magma usually mean a less dramatic eruption, often causing streams of lava to ooze from the vent.The mountain-like mounds that we associate with volcanoes are what remain after the material spewed during eruptions has collected and hardened around the vent. This can happen over a period of weeks or many millions of years.A large eruption can be extremely dangerous for people living near a volcano. Flows of searing lava, which can reach 2,000 degrees Fahrenheit (1,250 degrees Celsius) or more, can be released, burning everything in its path, including whole towns. Wildfires
(Burn baby Burn) Uncontrolled blazes fueled by weather, wind, and dry underbrush, wildfires can burn acres of landand consume everything in their pathsin mere minutes.On average, more than 100,000 wildfires, also called wildland fires or forest fires, clear 4 million to 5 million acres (1.6 million to 2 million hectares) of land in the U.S. every year. In recent years, wildfires have burned up to 9 million acres (3.6 million hectares) of land. A wildfire moves at speeds of up to 14 miles an hour (23 kilometers an hour), consuming everythingtrees, brush, homes, even humansin its path.There are three conditions that need to be present in order for a wildfire to burn, which firefighters refer to as the fire triangle: fuel, oxygen, and a heat source. Fuel is any flammable material surrounding a fire, including trees, grasses, brush, even homes. The greater an area's fuel load, the more intense the fire. Air supplies the oxygen a fire needs to burn. Heat sources help spark the wildfire and bring fuel to temperatures hot enough to ignite. Lightning, burning campfires or cigarettes, hot winds, and even the sun can all provide sufficient heat to spark a wildfire.Although four out of five wildfires are started by people, nature is usually more than happy to help fan the flames. Dry weather and drought convert green vegetation into bone-dry, flammable fuel; strong winds spread fire quickly over land; and warm temperatures encourage combustion. When these factors come together all that's needed is a sparkin the form of lightning, arson, a downed power line, or a burning campfire or cigaretteto ignite a blaze that could last for weeks and consume tens of thousands of acres.
Avalanche While avalanches are sudden, the warning signs are almost always numerous before they let loose. Yet in 90 percent of avalanche incidents, the snow slides are triggered by the victim or someone in the victim's party. Avalanches kill more than 150 people worldwide each year. Most are snowmobilers, skiers, and snowboarders. Many avalanches are small slides of dry powdery snow that move as a formless mass. These "sluffs" account for a tiny fraction of the death and destruction wrought by their bigger, more organized cousins. Disastrous avalanches occur when massive slabs of snow break loose from a mountainside and shatter like broken glass as they race downhill. These moving masses can reach speeds of 80 miles (130 kilometers) per hour within about five seconds. Victims caught in these events seldom escape. Avalanches are most common during and in the 24 hours right after a storm that dumps 12 inches (30 centimeters) or more of fresh snow. The quick pileup overloads the underlying snowpack, which causes a weak layer beneath the slab to fracture. The layers are an archive of winter weather: Big dumps, drought, rain, a hard freeze, and more snow. How the layers bond often determines how easily one will weaken and cause a slide THE END Blizzards
(Is it me or is it cold in here) A blizzard is a heavy snowstorm with very cold temperatures, sustained winds of at least 35mph, and visibility of less than 0.25 miles. When a mass of polar air and warm air meet, the polar air pushes the warm air up and settles in the atmosphere where the water vapor forms snow clouds. Then winds and low temperatures combine with the snow to create a blizzard. During blizzards it can be difficult to see or breathe. Blizzards can kill people, cause traffic accidents, and bring cities to a halt.