National Geographic : 2014 Dec
Planet Earth EXPLORE PHOTO: REBECCA HALE, NGM STAFF. ART: SAMANTHA WELKER SOURCE: SANJIVA LELE, STANFORD UNIVERSITY Riding on Rough Air Some skies aren’t so friendly, thanks to unpredictable bouts of turbulence. A United Airlines flight in February hit such rough air that a baby was thrown into the air (but wasn’t harmed), one passen- ger’s head made a dent in the ceiling, and five people later went to the hospital. Because of climate change, the extreme weather events that breed turbulence “are likely to become more fre- quent or more intense,” says a U.S. Environmental Protection Agency report. “Flight plans avoid known regions of severe turbulence, but these regions move, and it is difficult to predict exactly where the severe turbulence is going to be,” says Sanjiva Lele of the Stanford-NASA Center for Turbulence Re- search. Help is on the way: Earlier this year one U.S. air- line debuted new turbulence detectors that use special radar to predict the levels and location of turbulence in a flight path. — Mark J. Miller WAKE FROM PLANES Much as a boat’s wake affects other craft, planes can suffer a major loss of control or altitude from wake tur- bulence. That’s why air traffic control times takeoffs and landings to avoid it. BAD WEATHER Bumpy rides occur when planes fly through thunderstorms or after a rain, when warm air and cool air mix. Planes try to rise above such phenomena, but most can’t fly higher than 45,000 feet. ALTERNATIVE ROCK Some strange things are turning up on Hawaii’s Kamilo Beach. They look like chunks of garbage but are actually pieces of a newly noted kind of stone. These “plastiglomer- ates” form when plastic litter melts in the heat of campfires and mixes with sand, basalt fragments, wood, and other de- bris. Sedimentologist Patricia Corcoran says that in Earth’s future geologic record the stones could serve as markers of the point in civilization when humans started using (and discarding) plastics on a grand scale. —Catherine Zuckerman CLEAR AIR TURBULENCE The most common form of turbulence, this movement is often associated with the edges of the jet stream, a persistent atmospheric motion pattern in the Northern Hemisphere. GRAVITY WAVES Air that is forced upward, such as over mountains and above thunderstorms, causes gravity waves. Turbulence over mountains is common as two different, large air masses suddenly meet.