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A helicopter prepares to rescue people at Everest Base Camp in Nepal on April 26.(Photo: Elia Saikaly, 6summitschallenge.com, via AP)
The idea that earthquakes and weather are somehow related dates back to the ancient Greeks. In the 4th century B.C., Aristotle proposed that the tremors were caused by wind trapped in underground caves.
The U.S. Geological Survey says that theory "led to a belief in earthquake weather, that because a large amount of air was trapped underground, the weather would be hot and calm before an earthquake. A later theory stated that earthquakes occurred in calm, cloudy conditions and were usually preceded by strong winds, fireballs and meteors."
Let's be clear: There is no such thing as earthquake weather. The USGS says there is an even chance an earthquake will occur in any type of weather condition. But major storm systems such as tropical cyclones (hurricanes or typhoons) associated with low-pressure changes in the atmosphere can induce fault slips and, in turn, earthquakes.
Earthquakes are caused when stresses in the Earth's outer layer push the sides of a fault together, eventually causing rocks to slip and release energy. That energy comes in waves and is what we feel during earthquakes. The link between low-pressure storm systems and earthquakes is not uniform.
When weather and earthquakes combine — as they did in the magnitude-7.8 Nepal quake a week ago — disaster can follow. Snow and ice resting near the highest points away from the Earth's core were shaken loose by a major subterranean tremor producing an avalanche that killed at least 19 people on Mount Everest. Overall more than 5,900 people died in the quake, which destroyed thousands of homes and buildings.
An avalanche is the product of weather's child, snow. When there is a rapid flow of snow down a hill or mountainside the event is technically defined as an avalanche. This is how it happens: While the temperature remains low, snowfall sticks to the surface. When temperatures increase, snow will slough off and slide down a slope.
Any number of disturbances, including loud noise or a skier's motion, can cause an avalanche. Even pollution in the Northeast can find its way to Europe, hitching a ride with prevailing winds and causing avalanches in the Alps. That's because snowpack conditions affect the likelihood of avalanches. Soot warms snow and ice faster, creating melt and weakening snow layers, which promulgates avalanches.
In the USA, avalanches kill more people in national forests than any other natural hazard, according to the National Avalanche Center. Its data show the 2014/2015 winter season marks a 20-year record low for avalanche fatalities despite this century seeing the highest number of deaths since 1950. On average, 25 to 30 people die each year as a result of avalanches. (For the record, the number of earthquakes has remained largely consistent over time, numbering 500,000 globally. California alone experiences 10,000 tremors per year.)
Most avalanches occur from January to March, but as the NAC observes, avalanche season isn't over; aberrant events can happen, as last week's earthquake did.
Most avalanches are on slopes steeper than 30 degrees. If you find yourself on or near a mountain or hillside this steep, take precautions, especially during or within two days after snowfall — when avalanches are apt to happen.
The NAC posts avalanche advisories on its website. If you are headed to the mountains, check for avalanche conditions. There are five steps the NAC says can keep you safe from avalanches:
• Get the training. That means learning about slopes, snowpacks and triggers.
• Get the forecast. Which means checking the weather and searching for advisories.
• Get the gear. Transceivers, shovels and probes are essential avalanche safety items.
• Get the picture. Recognize red flags and trailhead conditions.
• Get out of harm's way. Matching your travel plan to conditions and traveling through potential danger zones single file can limit risks.
It's extremely difficult to survive an avalanche. Snow packs you in and limits movement. It may be impossible to figure out which way is up to try to dig out. (Although dribbling is one way to know which way is up or down — your spit will fall with gravity.)
Avalanche survival rates plummet after about 15 minutes for those who do not die from initial trauma.
There may be no such thing as earthquake weather to help determine if an avalanche might be set in motion, but there are some steps you can take to help you survive this kind of disaster. Learn to prepare.
Thomas M. Kostigen is the founder of TheClimateSurvivalist.com and a New York Times best-selling author and journalist. He is the National Geographic author of "The Extreme Weather Survival Guide: Understand, Prepare, Survive, Recover" and the NG Kids book" Extreme Weather: Surviving Tornadoes, Tsunamis, Hailstorms, Thundersnow, Hurricanes and More!" Follow him @weathersurvival, or e-mail[email protected]
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