10 Ways to Destroy Earth

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10 Existence failure

 

You will need: nothing

Method: No method. Simply sit back and twiddle your thumbs as, completely by chance, all 200,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 atoms making up the planet Earth suddenly, simultaneously and spontaneously cease to exist. Note: the odds against this actually ever occurring are considerably greater than a googolplex to one. Failing this, some kind of arcane (read: scientifically laughable) probability-manipulation device may be employed.


Utter, utter rubbish.

9 Gobbled up by stranglets

You will need: A stable stranglet

Method: Hijack control of the Relativistic Heavy Ion Collider in Brookhaven National Laboratory, Long Island, New York. Use the RHIC to create and maintain a stable strangelet. Keep it stable for as long as it takes to absorb the entire Earth into a mass of strange quarks. Keeping the strangelet stable is incredibly difficult once it has absorbed the stabilizing machinery, but creative solutions may be possible.

A while back, there was some media hoo-hah about the possibility of this actually happening at the RHIC, but in actuality the chances of a stable strangelet forming are pretty much zero.

Earth's final resting place: a huge glob of strange matter.

8 Sucked into a microscopic black hole

You will need: a microscopic black hole. Note that black holes are not eternal, they evaporate due to Hawking radiation. For your average black hole this takes an unimaginable amount of time, but for really small ones it could happen almost instantaneously, as evaporation time is dependent on mass. Therefore you microscopic black hole must have greater than a certain threshold mass, roughly equal to the mass of Mount Everest. Creating a microscopic black hole is tricky, since one needs a reasonable amount of neutronium, but may possibly be achievable by jamming large numbers of atomic nuclei together until they stick. This is left as an exercise to the reader.

Method: simply place your black hole on the surface of the Earth and wait. Black holes are of such high density that they pass through ordinary matter like a stone through the air. The black hole will plummet through the ground, eating its way to the center of the Earth and all the way through to the other side: then, it'll oscillate back, over and over like a matter-absorbing pendulum. Eventually it will come to rest at the core, having absorbed enough matter to slow it down. Then you just need to wait, while it sits and consumes matter until the whole Earth is gone.

Highly, highly unlikely. But not impossible.

Earth's final resting place: a singularity of almost zero size, which will then proceed to happily orbit the Sun as normal.

Source: "The Dark Side Of The Sun," by Terry Pratchett. It is true that the microscopic black hole idea is an age-old science fiction mainstay which predates Pratchett by a long time, he was my original source for the idea, so that's what I'm putting.

7 Blown up by matter/antimatter reaction

 

You will need: 2,500,000,000,000 tons of antimatter

Antimatter - the most explosive substance possible - can be manufactured in small quantities using any large particle accelerator, but this will take some considerable time to produce the required amounts. If you can create the appropriate machinery, it may be possible - and much easier - simply to "flip" 2.5 trillion tons of matter through a fourth dimension, turning it all to antimatter at once.

Method: This method involves detonating a bomb so big that it blasts the Earth to pieces.

How hard is that?

The gravitational binding energy of a planet of mass M and radius R is - if you do the lengthy calculations - given by the formula E=(3/5)GM^2/R. For Earth, that works out to roughly 224,000,000,000,000,000,000,000,000,000,000 Joules. The Sun takes nearly a WEEK to output that much energy. Think about THAT.

To liberate that much energy requires the complete annihilation of around 2,500,000,000,000 tonnes of antimatter. That's assuming zero energy loss to heat and radiation, which is unlikely to be the case in reality: You'll probably need to up the dose by at least a factor of ten. Once you've generated your antimatter, probably in space, just launch it en masse towards Earth. The resulting release of energy (obeying Einstein's famous mass-energy equation, E=mc^2) should be sufficient to split the Earth into a thousand pieces.

Earth's final resting place: A second asteroid belt around the Sun.

Earliest feasible completion date: AD 2500. Of course, if it does prove possible to manufacture antimatter in the sufficiently large quantities you require - which is not necessarily the case - then smaller antimatter bombs will be around long before then.

6 Destroyed by vacuum energy detonation

Method: This is a fun one. Contemporary scientific theories tell us that what we may see as vacuum is only vacuum on average, and actually thriving with vast amounts of particles and antiparticles constantly appearing and then annihilating each other. It also suggests that the volume of space enclosed by a light bulb contains enough vacuum energy to boil every ocean in the world. Therefore, vacuum energy could prove to be the most abundant energy source of any kind. Which is where you come in. All you need to do is figure out how to extract this energy and harness it in some kind of power plant - this can easily be done without arousing too much suspicion - then surreptitiously allow the reaction to run out of control. The resulting release of energy would easily be enough to annihilate all of planet Earth and probably the Sun too.

Slightly possible.

Earth's final resting place: a rapidly expanding cloud of particles of varying size.

Earliest feasible completion date: 2060 or so.

Source: "3001: The Final Odyssey," by Arthur C. Clarke

5 Sucked into a giant black hole

 

You will need: a black hole, extremely powerful rocket engines, and, optionally, a large rocky planetary body. The nearest black hole to our planet is 1600 light years from Earth in the direction of Sagittarius, orbiting V4641.

Method: after locating your black hole, you need get it and the Earth together. This is likely to be the most time-consuming part of this plan. There are two methods, moving Earth or moving the black hole, though for best results you'd most likely move both at once.

Very difficult, but definitely possible.

Earth's final resting place: part of the mass of the black hole.

Earliest feasible completion date: I do not expect the necessary technology to be available until AD 3000, and add at least 800 years for travel time. (That's in an external observer's frame of reference and assuming you move both the Earth and the black hole at the same time.)

Sources: "The Hitch Hiker's Guide To The Galaxy," by Douglas Adams; SPACE.com

4 Meticulously and systematically deconstructed

You will need: a powerful mass driver, or ideally lots of them; ready access to roughly 2*10^32J

Method: Basically, what we're going to do here is dig up the Earth, a big chunk at a time, and boost the whole lot of it into orbit. Yes. All six sextillion tons of it. A mass driver is a sort of oversized electromagnetic railgun, which was once proposed as a way of getting mined materials back from the Moon to Earth - basically, you just load it into the driver and fire it upwards in roughly the right direction. We'd use a particularly powerful model - big enough to hit escape velocity of 11 kilometers per second even after atmospheric considerations - and launch it all into the Sun or randomly into space.

Alternate methods for boosting the material into space include loading the extracted material into space shuttles or taking it up via space elevator. All these methods, however, require a - let me emphasize this - titanic quantity of energy to carry out. Building a Dyson sphere ain't gonna cut it here. (Note: Actually, it would. But if you have the technology to build a Dyson sphere, why are you reading this?) See No. 6 for a possible solution.

If we wanted to and were willing to devote resources to it, we could start this process RIGHT NOW. Indeed, what with all the gunk left in orbit, on the Moon and heading out into space, we already have done.

Earth's final resting place: Many tiny pieces, some dropped into the Sun, the remainder scattered across the rest of the Solar System.

Earliest feasible completion date: Ah. Yes. At a billion tons of mass driven out of the Earth's gravity well per second: 189,000,000 years.

Source: this method arose when Joe Baldwin and I knocked our heads together by accident.

3 Pulverized by impact with blunt instrument

You will need: a big heavy rock, something with a bit of a swing to it... perhaps Mars

Method: Essentially, anything can be destroyed if you hit it hard enough. ANYTHING. The concept is simple: find a really, really big asteroid or planet, accelerate it up to some dazzling speed, and smash it into Earth, preferably head-on but whatever you can manage. The result: an absolutely spectacular collision, resulting hopefully in Earth (and, most likely, our "cue ball" too) being pulverized out of existence - smashed into any number of large pieces which if the collision is hard enough should have enough energy to overcome their mutual gravity and drift away forever, never to coagulate back into a planet again.

A brief analysis of the size of the object required can be found here. Falling at the minimal impact velocity of 11 kilometers per second and assuming zero energy loss to heat and other energy forms, the cue ball would have to have roughly 60% of the mass of the Earth. Mars, the next planet out, "weighs" in at about 11% of Earth's mass, while Venus, the next planet in and also the nearest to Earth, has about 81%. Assuming that we would fire our cue ball into Earth at much greater than 11km/s (I'm thinking more like 50km/s), either of these would make great possibilities.

Obviously a smaller rock would do the job, you just need to fire it faster. A 10,000,000,000,000-tonne asteroid at 90% of light speed would do just as well. See the Guide to moving Earth for useful information on maneuvering big hunks of rock across interplanetary distances.

Pretty plausible.

Earth's final resting place: a variety of roughly Moon-sized chunks of rock, scattered haphazardly across the greater Solar System.

Earliest feasible completion date: AD 2500, maybe?

Source: This method suggested by Andy Kirkpatrick

2 Eaten by von Neumann machines

 

Method: A von Neumann machine is any device that is capable of creating an exact copy of itself given nothing but the necessary raw materials. Create one of these that subsists almost entirely on iron, magnesium, aluminum and silicon, the major elements found in Earth's mantle and core. It doesn't matter how big it is as long as it can reproduce itself exactly in any period of time. Release it into the ground under the Earth's crust and allow it to fend for itself. Watch and wait as it creates a second von Neumann machine, then they create two more, then they create four more. As the population of machines doubles repeatedly, the planet Earth will, terrifyingly soon, be entirely eaten up and turned into a swarm of potentially sextillions of machines. Technically your objective would now be complete - no more Earth - but if you want to be thorough then you can command your VNMs to hurl themselves, along with any remaining trace elements, into the Sun. This hurling would have to be achieved using rocket propulsion of some sort, so be sure to include this in your design.

So crazy it might just work.

Earth's final resting place: the bodies of the VNMs themselves, then a small lump of iron sinking into the Sun.

Earliest feasible completion date: Potentially 2045-2050, or even earlier.

Source: "2010: Odyssey Two," by Arthur C. Clarke

1 Hurled into the Sun

 

Method: Hurl the Earth into the Sun. Sending Earth on a collision course with the Sun is not as easy as one might think; even though you don't actually have to literally hit the Sun (send the Earth near enough to the Sun (within the Roche limit), and tidal forces will tear it apart), it's surprisingly easy to end up with Earth in a loopy elliptical orbit which merely roasts it for four months in every eight. But careful planning can avoid this.

This is impossible at our current technological level, but will be possible one day, I'm certain. In the meantime, may happen by freak accident if something comes out of nowhere and randomly knocks Earth in precisely the right direction. Earth's final resting place: a small globule of vaporized iron sinking slowly into the heart of the Sun.

Earliest feasible completion date: Via act of God: 25 years' time. Any earlier and we'd have already spotted the asteroid in question. Via human intervention: given the current level of expansion of space technology, 2250 at best.

Source: "Infinity Welcomes Careful Drivers," by Grant Naylor

Top 10 pictures japan : before and after

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Japan before and after Tsunami


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 source : http://www.msnbc.msn.com/id/42064847/ns/world_news-asiapacific

9 Natural Disasters

1. Tornadoes

Killer Wind Funnels

Photograph by Carsten Peter

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.

2. Tsunamis

Killer Waves

Photograph by Deshakalyan Chowdhury/AFP/Getty Images

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.

3. Earthquakes

Seismic Destruction

Photograph by Mosanori Kobayashi

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.

4. Hurricanes

Engines of Destruction

Photograph courtesy NASA/GSFC

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.

5. Volcanoes

Earth's Fiery Power

Photograph courtesy NASA Earth Observatory

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.

6. Avalanches 

Photograph by Marc Muench/Getty Images

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.

Storminess, temperature, wind, slope steepness and orientation (the direction it faces), terrain, vegetation, and general snowpack conditions are all factors that influence whether and how a slope avalanches. Different combinations of these factors create low, moderate, considerable, and high avalanche hazards.

If caught in an avalanche, try to get off the slab. Not easy, in most instances. Skiers and snowboarders can head straight downhill to gather speed then veer left or right out of the slide path. Snowmobilers can punch the throttle to power out of harm's way. No escape? Reach for a tree. No tree? Swim hard. The human body is three times denser than avalanche debris and will sink quickly. As the slide slows, clear air space to breathe. Then punch a hand skyward.

Once the avalanche stops, it settles like concrete. Bodily movement is nearly impossible. Wait—and hope—for a rescue. Statistics show that 93 percent of avalanche victims survive if dug out within 15 minutes. Then the survival rates drop fast. After 45 minutes, only 20 to 30 percent of victims are alive. After two hours, very few people survive.

7. Wildfires

Dry, Hot, and Windy

Photograph by Mark Thiessen

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.

8. Floods

Photograph by Jim Richardson

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.

9. Lightning

Photograph by William R. Curstinger

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 : environment.nationalgeographic.com

helicopter crash

5 pictures helicopter crash