Interesting Facts about Iceland's Volcano

Iceland's volcano: 9 Interesting facts

As the eruption of Eyjafjallajökull continues to cause travel chaos around the world, a look at some of the weirder stories to come out of the disaster

CALCULATING CALIFORNIA'S TSUNAMI RISK

The threat that Pacific Ocean tsunamis pose to California's coastline just got its first comprehensive study, a milestone in understanding and preparing for the rare, but devastating, waves.

Following the devastating 2004 tsunami in southeast Asia, scientists scrambled to provide county and municipal emergency planners with an estimate of how vulnerable their coastlines were to tsunamis.

Some 350,000 people live in the path of a worst-case scenario, though overall, the risk to life and property is less than previously thought, state officials reported.

"We used one elevation for the whole state. We just drew a line at 30 feet up from sea level," Rick Wilson of the California Geological Survey said.

With the new effort, Wilson and a team of researchers developed detailed maps of what parts of the coast would flood during a range of disaster scenarios.

Overall they found that most surges wouldn't come close to the 30-foot line they had previously assumed.

"Even if we don't show higher inundation, this really helps emergency planners," Wilson said.

Check the Video Out: Tsunami Warning Center Uses Top Technology

The Washington state coastline is the most tsunami-prone area in the United States. Kasey-Dee Gardner reports on one of the most sophisticated tsunami warning systems in the world.

This is particularly true on the outskirts of San Diego, where the city of Coronado sits on a low-lying peninsula. Old tsunami maps predicted the entire town would be submerged, and local officials feared that they would be forced into a desperate attempt to airlift 24,000 people out of harm's way.

New maps predict the worst waves would reach elevations of 15 to 18 feet.

Large earthquakes can generate tsunamis just about anywhere along the Pacific "Ring of Fire," a 40,000-kilometer-long chain of tectonic unrest that includes Japan, Kamchatka, the Alaska's Aleutian Islands, the Andes in South America and California.

The team considered threats from all of these regions, and found that a magnitude 9.0 or greater earthquake in the eastern Aleutians would be the most dangerous for California.

In particular, Santa Cruz could see waves of 20 to 25 feet. Even the interior of the San Francisco Bay would not be spared, with 10-12 foot waves reaching Alameda, and eight- to 10-foot surges spilling into the towns of Sausalito and San Rafael.

"Any emergency responder can look at these maps and see what it means for them and their neighbors." Dale Cox of the United States Geological Survey in Sacramento said. "It's intellectually accessible to the public, too. If people are asking 'gee, where do I go?' these maps will tell you. People can look at these and easily tell what's in it for them."

Source: Discovery News

Dramatic Flood Rescue Explained

Check this out: Dramatic Flood Rescue Explained:

The daring rescue of an elderly woman from a flooded river in Missouri is caught on video. Jorge Ribas interviews one of the Missouri National Guard citizen-soldiers to get the details of the mission.
Source: Discovery News

DEADLY QUAKES INSIDE CONTINENTAL PLATES

According to researchers, the main reason for high death tolls within continental interiors is because inland quake zones are poorly mapped.

Our perception of seismic risk is skewed into thinking earthquakes at plate boundaries are more deadly. We're wrong.

Knowledge of seismic risk is badly skewed in favor of earthquakes that occur on plate boundaries, such as the March 11 temblor that hit northeast Japan, rather than those that strike deep inland, a pair of scientists said on Sunday.

In commentary appearing in the journal Nature Geoscience, Philip England of Oxford University and James Jackson of Cambridge University say that in seismic terms, the 9.0-magnitude Sendai quake was "a remarkable story of resilience."

Good civic training and building construction meant that the death rate was "impressively low," they said. Around 25,000 people died, or 0.4 percent of those exposed to the event, and most of these died from the tsunami that followed.

THE GIST

·     Earthquake preparedness is high around seismically active tectonic plate boundaries, often saving many lives and structures.

·   Quake death rates within continental interiors are higher than that of continental plate boundaries.

·   Their faults are often very complex and slow-moving, sometimes taking thousands of years to rupture.

The March 11 event occurred on a plate boundary, where the jigsaw of plates that float on Earth's crust jostle and grind and slide under each other.

England and Jackson say plate boundaries are relatively well-studied, but a far greater threat lurks in continental inland areas.

"Death rates in earthquakes within continental interiors have often exceeded five percent and can be as high as 30 percent," they warn.

According to their count, over the past 120 years, there have been around 130 quakes around the world where a thousand people or more have died.

Of these, about 100 have occurred in continental interiors, causing 1.4 million deaths, whereas earthquakes at plate boundaries have inflicted 800,000 deaths, roughly half of them by tsunamis.

Among the inland killers were those in Bam, Iran, which cost 30,000 lives in 2003; in Muzzafarabad, Pakistan, which led to 75,000 deaths in 2005; and the 2008 Wenchuan quake in China in 2008 in which 70,000 died.

The main reason for these high tolls is because inland quake zones are poorly mapped, the commentary says.

Their faults are often very complex and slow-moving, sometimes taking hundreds or even thousands of years to build up tension to the point where they rupture.

Jackson and England call for the study of inland faults to be given the same priority as boundary faults, starting with the 10 million square kilometers (3.86 million sq. miles) of the Alpine-Himalayan belt, which stretches from Italy, Greece and Turkey, across the Middle East, Iran and central Asia, to China.

"The severity of this threat is increasing rapidly as millions of people every year migrate into mega-cities in vulnerable locations, many of which were devastated by earthquakes in the past, when their populations were much smaller."

Source: Discovery News

TORNADO STRIKES MISSOURI TOWN, KILLING 116

May 23, 2011 - The deadliest single tornado to strike the United States in nearly 60 years has reduced the Missouri town of Joplin to rubble, ripping buildings apart and killing at least 116 people.

The deadliest single tornado to strike the United States in nearly 60 years has reduced the Missouri town of Joplin to rubble, ripping buildings apart and killing at least 116 people.

Disaster struck on Sunday evening when, with little warning, the monster twister tore a strip six miles long and more than a 1/2 mile wide through the center of the town.

Rescuers worked through the night to try to find people trapped in their homes, relying on torchlight as they listened for terrified cries from survivors piercing through the blackness.

Heavy winds and strong rain forced teams to halt the effort on Monday morning and some rescuers took advantage of the brief respite to catch a bit of much-needed sleep inside one badly damaged bank.

THE GIST

·         Local media reports that 116 people have been killed after Joplin took a "direct hit" from a tornado.

·         Missouri Governor has declared a state of emergency as the threat of further tornadoes continues.

Missouri Governor Jay Nixon declared a state of emergency late Sunday and activated the National Guard to help out after one of the worst disasters in the state's history.

President Barack Obama called Nixon and offered his condolences to those affected, assuring the governor that the Federal Emergency Management Agency (FEMA) would provide whatever assistance was needed.

"The president has directed FEMA Administrator Craig Fugate to travel to Missouri to ensure the state has all the support it needs," a White House statement said, adding a FEMA team had already been dispatched.

Caring for the injured was made more difficult because the main hospital, Saint John's Regional Medical Center, had to be evacuated after suffering a direct hit -- the tornado ripped off its roof and smashed all its windows.

Media reported that cries could still be heard early Monday from survivors trapped in the wreckage, with the latest tragedy coming less than a month after a horrific tornado outbreak left 354 dead across seven U.S. states.

Authorities estimated that up to 30 percent of Joplin, which lies near the border with Oklahoma and Kansas, had been damaged by the tornado, which experts said carried winds of up to 200 miles per hour.

It was the deadliest of 46 tornadoes reported to the National Weather Service in seven states on Sunday.

"It's a war zone," Scott Meeker of the Joplin Globe newspaper said.

"We've got hundreds of wounded being treated at Memorial Hall (hospital), but they were quickly overwhelmed and ran out of supplies, so they've opened up a local school as a triage center."

Obama earlier sent his "deepest condolences" to victims and said the federal government stood ready to help Americans as needed.

"Michelle and I send our deepest condolences to the families of all those who lost their lives in the tornadoes and severe weather that struck Joplin, Missouri, as well as communities across the Midwest today," the president said in a statement sent from Air Force One as he flew to Europe.

"We commend the heroic efforts by those who have responded and who are working to help their friends and neighbors at this very difficult time."

People in Joplin clawed through the rubble looking for friends, family and neighbors after the storm tore buildings apart and turned cars into crumpled heaps of metal.

Flames and thick black smoke poured out of the wreckage of shattered homes, and water gushed out of broken pipes as shocked survivors surveyed the damage, early photos showed.

A tangled medical helicopter lay in the rubble outside Saint John's Regional Medical Center.

Jeff Law, 23, was able to take shelter in a storm cellar and was overwhelmed by what he saw when he emerged.

"I've lived in this neighborhood my entire life, and I didn't know where I was," Law told the Springfield News-Leader. "Everything was unrecognizable, completely unrecognizable. It's like Armageddon."

The emergency manager at the neighboring county of Springfield-Greene was told that at least 24 people were killed before he could rush over to help, a spokeswoman said.

Officials said the last twister to wreak such loss of life occurred in 1953 in Worcester, Massachusetts, when a tornado killed 90 people.

On Saturday, a deadly tornado pummeled the east Kansas town of Reading, killing a man and damaging an estimated 80 percent of Reading's structures, mostly wood-frame buildings.

Meanwhile, a tornado was also responsible for the death of one person in Minneapolis, Minnesota, on Sunday, authorities said. At least 30 others in that city and its suburbs were injured.

Source: Discovery News

ICELAND VOLCANO ERUPTS

Satellite image of Grimsvotn erupting in 2004.

The Grimsvoetn volcano under Iceland's largest glacier began erupting Saturday, the Icelandic Meteorological Office said, reporting a tall plume of smoke rising from the crater.

"An eruption at Grimsvoetn has started and there's an airplane on its way there now to investigate further," Haraldur Eirkisson of the office told AFP.

"There was a cloud rising up from Grimsvoetn around 1900 GMT and at just before 2000 GMT it had reached an altitude of 11 kilometers (6.8 miles)," he added.

Another meteorologist at the same office, Fridjon Magnusson, told AFP less than two hours later that the column of smoke had swelled to reach an altitude of 20 kilometers.

Grimsvoetn is Iceland's most active volcano, having erupted nine times between 1922 and 2004. It lies beneath the Vatnajoekull glacier in the southeast of the North Atlantic island nation.

The eruption in April last year of Iceland's Eyjafjoell volcano, southwest of Grimsvoetn, shut down large swathes of European airspace for almost a month amid fears the volcanic ash could wreak havoc on aircraft engines.

The Gist

·    Grimsvoetn volcano, located beneath Iceland's Vatnajoekull glacier, last erupted      in 2004.

·       Last year, Iceland's Eyjafjoell volcano, southwest of Grimsvoetn, shut down large swathes of European airspace for almost a month.

·    For now, it is not known if Grimsvoetn will produce the troublesome fine ash   Eyjafjoell generated.

No two volcanic eruptions are the same, and it remained unclear late Saturday if the new eruption threatened to emit a similar kind of ash -- fine, with very sharp particles -- like the massive plume that burst from Eyjafjoell.

"The eruption has not yet spread very far, and is still looming over the Vatnajoekull glacier," Magnusson pointed out.

"These are just the first few hours of the eruption. We can't say yet whether this will have an effect on air traffic like Eyjafjoell," he added.

The problem with last year's eruption, which caused the planet's biggest air space shutdown since World War II, was according to the researchers that it happened under a glacier, bursting through 200-300 meters of ice.

It was the "interaction between the cold water and the hot magma that made the particles really tiny," and therefore especially dangerous to aircraft, Susan Stipp, a professor at the Nano-Science Centre at the University of Copenhagen, told AFP late last month.

"The (ash) particles were small so they went high and far. They were sharp, so they were a danger to airplane windows. It's like sand-blasting the airplane. And they were small and could melt at temperatures common in jet engines ... and could cause failure," she told AFP.

While Saturday's eruption had sent smoke high in the sky, Magnusson pointed out that there so far was only "heavy ash at the bottom of the bloom (that) has not reached high heights."

Bjarni Steinthorsson, a farmer who lives near the Vatnajoekull glacier, meanwhile told the Morgunbladid daily's website small amounts of ash had begun falling in the area and "the snow is getting darker."

He said that he expected more ash to fall overnight, although what happened would depend on the direction of the winds, which were currently almost still at the eruption site.

Iceland's State Road Authority meanwhile announced late Saturday it had temporarily closed a road near the glacier that is part of the national highway system.

Grimsvoetn is also located under a glacier, in an enormous, eight-kilometer (five-mile) diameter caldera -- a collapsed volcanic crater -- near the center of the Vatnajoekull icefield.

When it last erupted in November 2004, volcanic ash fell as far away as mainland Europe and caused minor disruptions in flights to and from Iceland.

Geologists had worried late last year the volcano was about to blow when they noticed a large river run caused by rapidly melting glacier ice.

Eruptions at Grimsvoetn traditionally result in massive flooding, although this has little impact since the surrounding areas are uninhabited.

Source: Discovery News

Facts about Hurricane Katrina

Facts about Hurricane Katrina

Hurricane Katrina was the costliest U.S. hurricane on record and one of the worst natural disasters in U. S. history. Hurricane Katrina will be remembered for its catastrophic flooding in New Orleans due to levee failure.

Facts about Wildfires

Uncontrolled blazes fueled by weather, wind, and dry underbrush, wildfires can burn acres of land—and consume everything in their paths—in 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 everything—trees, brush, homes, even humans—in 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 spark—in the form of lightning, arson, a downed power line, or a burning campfire or cigarette—to ignite a blaze that could last for weeks and consume tens of thousands of acres.

These violent infernos occur around the world and in most of the 50 states, but they are most common in the U.S. West, where heat, drought, and frequent thunderstorms create perfect wildfire conditions. Montana, Idaho, Wyoming, Washington, Colorado, Oregon, and California experience some of the worst conflagrations in the U.S. In California wildfires are often made worse by the hot, dry Santa Ana winds, which can carry a spark for miles.

Firefighters fight wildfires by depriving them of one or more of the fire triangle fundamentals. Traditional methods include water dousing and spraying fire retardants to extinguish existing fires. Clearing vegetation to create firebreaks starves a fire of fuel and can help slow or contain it. Firefighters also fight wildfires by deliberately starting fires in a process called controlled burning. These prescribed fires remove undergrowth, brush, and ground litter from a forest, depriving a wildfire of fuel.

Although often harmful and destructive to humans, naturally occurring wildfires play an integral role in nature. They return nutrients to the soil by burning dead or decaying matter. They also act as a disinfectant, removing disease-ridden plants and harmful insects from a forest ecosystem. And by burning through thick canopies and brushy undergrowth, wildfires allow sunlight to reach the forest floor, enabling a new generation of seedlings to grow.

Source: National Geographic

Facts about 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. Boulders of hardening lava can rain down on villages. Mud flows from rapidly melting snow can strip mountains and valleys bare and bury towns. Ash and toxic gases can cause lung damage and other problems, particularly for infants and the elderly. Scientists estimate that more than 260,000 people have died in the past 300 years from volcanic eruptions and their aftermath.

Volcanoes tend to exist along the edges between tectonic plates, massive rock slabs that make up Earth's surface. About 90 percent of all volcanoes exist within the Ring of Fire along the edges of the Pacific Ocean.

About 1,900 volcanoes on Earth are considered active, meaning they show some level of activity and are likely to explode again. Many other volcanoes are dormant, showing no current signs of exploding but likely to become active at some point in the future. Others are considered extinct.

Source: National Geographic

Facts about Tsunami

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. They may even be launched, as they frequently were in Earth’s ancient past, by the impact of a large meteorite plunging into an ocean.

Tsunamis race across the sea at up to 500 miles (805 kilometers) an hour—about as fast as a jet airplane. At that pace they can cross the entire expanse of the Pacific Ocean in less than a day. And their long wavelengths mean they lose very little energy along the way.

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.

A tsunami’s trough, the low point beneath the wave’s crest, often reaches shore first. When it does, it produces a vacuum effect that sucks coastal water seaward and exposes harbor and sea floors. This retreating of sea water is an important warning sign of a tsunami, because the wave’s crest and its enormous volume of water typically hit shore five minutes or so later. Recognizing this phenomenon can save lives.

A tsunami is usually composed of a series of waves, called a wave train, so its destructive force may be compounded as successive waves reach shore. People experiencing a tsunami should remember that the danger may not have passed with the first wave and should await official word that it is safe to return to vulnerable locations.

Some tsunamis do not appear on shore as massive breaking waves but instead resemble a quickly surging tide that inundates coastal areas.

The best defense against any tsunami is early warning that allows people to seek higher ground. The Pacific Tsunami Warning System, a coalition of 26 nations headquartered in Hawaii, maintains a web of seismic equipment and water level gauges to identify tsunamis at sea. Similar systems are proposed to protect coastal areas worldwide.

Source: National Geographic

Facts about Tornadoes

Tornadoes are vertical funnels of rapidly spinning air. Their winds may top 250 miles (400 kilometers) an hour and can clear-cut a pathway a mile (1.6 kilometers) wide and 50 miles (80 kilometers) long.

Twisters are born in thunderstorms and are often accompanied by hail. Giant, persistent thunderstorms called supercells spawn the most destructive tornadoes.

These violent storms occur around the world, but the United States is a major hotspot with about a thousand tornadoes every year. "Tornado Alley," a region that includes eastern South Dakota, Nebraska, Kansas, Oklahoma, northern Texas, and eastern Colorado, is home to the most powerful and destructive of these storms. U.S. tornadoes cause 80 deaths and more than 1,500 injuries per year.

A tornado forms when changes in wind speed and direction create a horizontal spinning effect within a storm cell. This effect is then tipped vertical by rising air moving up through the thunderclouds.

The meteorological factors that drive tornadoes make them more likely at some times than at others. They occur more often in late afternoon, when thunderstorms are common, and are more prevalent in spring and summer. However, tornadoes can and do form at any time of the day and year.

Tornadoes' distinctive funnel clouds are actually transparent. They become visible when water droplets pulled from a storm's moist air condense or when dust and debris are taken up. Funnels typically grow about 660 feet (200 meters) wide.

Tornadoes move at speeds of about 10 to 20 miles (16 to 32 kilometers) per hour, although they've been clocked in bursts up to 70 miles (113 kilometers) per hour. Most don't get very far though. They rarely travel more than about six miles (ten kilometers) in their short lifetimes.

Tornadoes are classified as weak, strong, or violent storms. Violent tornadoes comprise only about two percent of all tornadoes, but they cause 70 percent of all tornado deaths and may last an hour or more.

People, cars, and even buildings may be hurled aloft by tornado-force winds—or simply blown away. Most injuries and deaths are caused by flying debris.

Tornado forecasters can't provide the same kind of warning that hurricane watchers can, but they can do enough to save lives. Today the average warning time for a tornado alert is 13 minutes. Tornadoes can also be identified by warning signs that include a dark, greenish sky, large hail, and a powerful train-like roar.

Source: National Geographic

Facts about Lightning

Lightning Can Strike Twice

Cloud-to-ground lightning bolts are a common phenomenon—about 100 strike Earth’s surface every single second—yet their power is extraordinary. Each bolt can contain up to one billion volts of electricity.

This enormous electrical discharge is caused by an imbalance between positive and negative charges. During a storm, colliding particles of rain, ice, or snow increase this imbalance and often negatively charge the lower reaches of storm clouds. Objects on the ground, like steeples, trees, and the Earth itself, become positively charged—creating an imbalance that nature seeks to remedy by passing current between the two charges.

A step-like series of negative charges, called a stepped leader, works its way incrementally downward from the bottom of a storm cloud toward the Earth. Each of these segments is about 150 feet (46 meters) long. When the lowermost step comes within 150 feet (46 meters) of a positively charged object it is met by a climbing surge of positive electricity, called a streamer, which can rise up through a building, a tree, or even a person. The process forms a channel through which electricity is transferred as lightning.

Some types of lightning, including the most common types, never leave the clouds but travel between differently charged areas within or between clouds. Other rare forms can be sparked by extreme forest fires, volcanic eruptions, and snowstorms. Ball lightning, a small, charged sphere that floats, glows, and bounces along oblivious to the laws of gravity or physics, still puzzles scientists.

Lightning is extremely hot—a flash can heat the air around it to temperatures five times hotter than the sun’s surface. This heat causes surrounding air to rapidly expand and vibrate, which creates the pealing thunder we hear a short time after seeing a lightning flash.

Lightning is not only spectacular, it’s dangerous. About 2,000 people are killed worldwide by lightning each year. Hundreds more survive strikes but suffer from a variety of lasting symptoms, including memory loss, dizziness, weakness, numbness, and other life-altering ailments.

Source: National Geographic

Facts about Hurricanes

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.

Hurricanes begin as tropical disturbances in warm ocean waters with surface temperatures of at least 80 degrees Fahrenheit (26.5 degrees Celsius). These low pressure systems are fed by energy from the warm seas. If a storm achieves wind speeds of 38 miles (61 kilometers) an hour, it becomes known as a tropical depression. A tropical depression becomes a tropical storm, and is given a name, when its sustained wind speeds top 39 miles (63 kilometers) an hour. 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.

Hurricanes are enormous heat engines that generate energy on a staggering scale. They draw heat from warm, moist ocean air and release it through condensation of water vapor in thunderstorms.

Hurricanes spin around a low-pressure center known as the “eye.” Sinking air makes this 20- to 30-mile-wide (32- to 48-kilometer-wide) area notoriously calm. But the eye is surrounded by a circular “eye wall” that hosts the storm’s strongest winds and rain.

These storms bring destruction ashore in many different ways. When a hurricane makes landfall it often produces a devastating storm surge that can reach 20 feet (6 meters) high and extend nearly 100 miles (161 kilometers). Ninety percent of all hurricane deaths result from storm surges.

A hurricane’s high winds are also destructive and may spawn tornadoes. Torrential rains cause further damage by spawning floods and landslides, which may occur many miles inland.

The best defense against a hurricane is an accurate forecast that gives people time to get out of its way. The National Hurricane Center issues hurricane watches for storms that may endanger communities, and hurricane warnings for storms that will make landfall within 24 hours.

Source: National Geographic

Facts about Floods

There are few places on Earth where people need not be concerned about flooding. Any place where rain falls is vulnerable, although rain is not the only impetus for flood.

A flood occurs when water overflows or inundates land that's normally dry. This can happen in a multitude of ways. Most common is when rivers or streams overflow their banks. Excessive rain, a ruptured dam or levee, rapid ice melting in the mountains, or even an unfortunately placed beaver dam can overwhelm a river and send it spreading over the adjacent land, called a floodplain. Coastal flooding occurs when a large storm or tsunami causes the sea to surge inland.

Most floods take hours or even days to develop, giving residents ample time to prepare or evacuate. Others generate quickly and with little warning. These flash floods can be extremely dangerous, instantly turning a babbling brook into a thundering wall of water and sweeping everything in its path downstream.

Disaster experts classify floods according to their likelihood of occurring in a given time period. A hundred-year flood, for example, is an extremely large, destructive event that would theoretically be expected to happen only once every century. But this is a theoretical number. In reality, this classification means there is a one-percent chance that such a flood could happen in any given year. Over recent decades, possibly due to global climate change, hundred-year floods have been occurring worldwide with frightening regularity.

Moving water has awesome destructive power. When a river overflows its banks or the sea drives inland, structures poorly equipped to withstand the water's strength are no match. Bridges, houses, trees, and cars can be picked up and carried off. The erosive force of moving water can drag dirt from under a building's foundation, causing it to crack and tumble.

In the United States, where flood mitigation and prediction is advanced, floods do about $6 billion worth of damage and kill about 140 people every year. A 2007 report by the Organization for Economic Cooperation and Development found that coastal flooding alone does some $3 trillion in damage worldwide. In China's Yellow River valley, where some of the world's worst floods have occurred, millions of people have perished in floods during the last century.

When floodwaters recede, affected areas are often blanketed in silt and mud. The water and landscape can be contaminated with hazardous materials, such as sharp debris, pesticides, fuel, and untreated sewage. Potentially dangerous mold blooms can quickly overwhelm water-soaked structures. Residents of flooded areas can be left without power and clean drinking water, leading to outbreaks of deadly waterborne diseases like typhoid, hepatitis A, and cholera.

But flooding, particularly in river floodplains, is as natural as rain and has been occurring for millions of years. Famously fertile floodplains like the Mississippi Valley in the American Midwest, the Nile River valley in Egypt, and the Tigris-Euphrates in the Middle East have supported agriculture for millennia because annual flooding has left millions of tons of nutrient-rich silt deposits behind.

Most flood destruction is attributable to humans' desire to live near picturesque coastlines and in river valleys. Aggravating the problem is a tendency for developers to backfill and build on wetlands that would otherwise act as natural flood buffers.

Many governments mandate that residents of flood-prone areas purchase flood insurance and build flood-resistant structures. Massive efforts to mitigate and redirect inevitable floods have resulted in some of the most ambitious engineering efforts ever seen, including New Orleans's extensive levee system and massive dikes and dams in the Netherlands. And highly advanced computer modeling now lets disaster authorities predict with amazing accuracy where floods will occur and how severe they're likely to be.

Facts about Earthquakes

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 plates—giant rock slabs that make up the Earth's upper layer—collide 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.

Loss of life can be avoided through emergency planning, education, and the construction of buildings that sway rather than break under the stress of an earthquake.

Source: National Geographic