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As spring progresses in North America, the days grow longer. Land temperatures rise, and warm, moist air from the Gulf of Mexico progressively drives back colder air masses from the Arctic. This annual shift brings on tornado season, which peaks in May and June. By late summer the Atlantic Ocean and Caribbean Sea reach their maximum temperature, bringing on hurricane season from July through September. Independent of the weather or time of year, volcanoes are brought to life year-round all over the globe by shifts in the rigid plates of the Earth's crust, the rise of magma from deep within the mantle, and other forces. One dreaded sign of volcanic or seismic activity under the sea is the tsunami, a sudden rise or wave of water inundating entire coastlines. All these natural disasters have their roots in fundamental Earth processes.
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• The Power of Tornadoes
Tornadoes generate the strongest winds known on Earth, up to 300 miles per hour.
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• Tornado Outbreaks
Once every 10 to 15 years, weather patterns produce nationwide tornado outbreaks such as the Super Outbreak of April 3–4, 1974, which saw 148 tornadoes striking the central and southern United States.
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• T. Theodore Fujita
The Fujita Scale, which ranks tornadoes from light to incredible, was invented by a Japanese scientist who moved to the United States in the 1950s
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• The Power of Volcanoes
A volcanic eruption is an awesome display of the Earth's power, shooting fountains of lava into the air, ejecting great clouds of ash-laden gas, or incinerating entire forests or towns with a mixture of hot gas and incandescent particles.
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• Mount St. Helens
The explosion of Mount St. Helens May 18, 1980, one of the greatest ever recorded in North America, brought complete darkness to Spokane, Washington, some 250 miles away.
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• Krakatoa
The explosion of Krakatoa (Krakatau) on a small uninhabited island between Sumatra and Java on August 26–27, 1883, was heard as far away as Australia and produced an ash cloud 50 miles high.
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• The Power of Tropical Cyclones
Tropical cyclones, known as hurricanes in the Caribbean and typhoons in East Asia, generate winds that can reach 150 miles per hour, along with torrential rains and a devastating phenomenon known as the storm surge, an elevation of the sea surface that can reach 20 feet above normal.
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• Hurricane and Typhoon Names
In the United States, names given to hurricanes are recycled every six years, while names of very intense, damaging, or otherwise newsworthy storms are retired.
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• Learning from Katrina
While there are many lessons to be learned from this tragic event, among the most significant involve the failures in the emergency management system of the United States.
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• The Power of Tsunamis
Tsunamis are usually caused by a submarine earthquake, by an underwater or coastal landslide, or by the eruption of a volcano. Traveling over the open ocean as fast as 500 miles per hour, they frequently appear onshore as powerful “run-ups” of rushing water that uproot trees, pull buildings off their foundations, carry boats far inshore, and wash away entire beaches, peninsulas, and other low-lying coastal formations.
• The Deadliest Tsunami
On Dec. 26, 2004, an undersea earthquake with a magnitude of 9.0 struck off the coast of the Indonesian island of Sumatra. Over the next seven hours, a tsunami triggered by the quake reached out across the Indian Ocean, devastating coastal areas as far away as East Africa and resulting in at least 225,000 casulties.
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Vintage newsreels show the terrible destruction that a tsunami brought to Hilo, Hawaii, in 1946.
View Video
Beginning in November 1963, an eruption of ash and lava from the seafloor off the coast of Iceland forms a new volcanic island, Surtsey.
View Video
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Note: Videos and animations may require Windows Media Player.
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A tsunami can cause coastal waters to rise 100 feet above normal in 10 to 15 minutes, yet on the open ocean it will pass under a ship completely unnoticed as a rise and fall of only a couple of feet.
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