Did Nepal Earthquake Change Mount Everest’s Height?
Scientists race against the clock to retrieve data that will also help them understand the devastating quake.
Updated on May 1.
The massive earthquake that struck Nepal Saturday likely caused permanent changes in the Earth’s surface and may have made Everest a little taller—or shorter, scientists say.
A team of geologists from the U.S. Geological Survey (USGS) is working on the problem now, but they need to retrieve data from a GPS station near Everest within the next 11 days, warns Kenneth Hudnut, a geophysicist who studies earthquakes with the USGS in Pasadena, California.
After that, new data will start recording over information about the quake, erasing the most detailed information on how much the station swayed back and forth and up and down. As a result, the geologists are scrambling to raise the funds to book helicopter time or to piggyback the mission on scheduled humanitarian efforts. (Learn more about the science of the Nepal quake.)
In the meantime, Hudnut and colleagues have been analyzing satellite and seismology data on Saturday’s estimated magnitude 7.8 earthquake, to better understand what happened and determine how likely future quakes may be. Preliminary models, which will need to be refined, suggest that Mount Everest and its surrounding area may have shifted by a few centimeters both vertically and horizontally, says Hudnut.
That jives with an estimate from James Jackson, a geologist at Cambridge University in England. At Everest, “the vertical motion is expected to be less than 10 centimeters [four inches] and the horizontal the same,” Jackson said via email.
Another spot moved two centimeters to the north, one centimeter to the east, and nothing in the vertical, Jackson added. That location, in Tibet 124 miles (200 kilometers) east of the earthquake’s epicenter, may be similar to what Everest experienced, he noted.
On April 29, scientists in Europe announced that preliminary satellite data suggests Everest may have actually decreased by about one inch (2.5 centimeters). Closer to Kathmandu, ground may have uplifted as much as three feet (one meter), the scientists noted, although more analysis is needed.
For a closer look, Hudnut hopes to retrieve data from a station called SYBC in a valley less than 17 miles (30 kilometers) from Everest’s peak. Since the station is no longer transmitting data, thanks to the quake, scientists will have to fly there and download it directly. Further information could eventually be provided if climbers can survey the top of the mountain with high-quality GPS units.
“We’re not just looking to see whether Everest went up or down, but we’re looking to understand what the whole Earth did and the science behind the earthquake,” says Hudnut. “For example, we want to know if the quake put additional stress on other faults in the area, which could lead to future earthquakes.”
Hudnut adds that the city of Kathmandu, which was closer to the epicenter than Everest and was heavily damaged by the temblor, may have seen movement of as much as a meter (three feet). Jackson says movement of the rocks along the fault near the city might have been as much as nine feet, or three meters.
Still, that doesn’t mean the city was simply shifted by that much, cautions Jackson, because the Earth’s crust deforms in complex, uneven ways. It may mean that parts of the ground underneath the city, or near it, moved relative to each other.
Time to Change Maps?
Asked if a new height for Everest will mean a change to National Geographic’s many map products, society Geographer Juan Valdés says he is watching the science closely.
National Geographic doesn’t rely on a single scientific agency for its data, he says, but rather reviews data compiled by as many sources as possible. In the case of Everest, that means data from agencies in China, Nepal, Europe, and beyond.
Quakes and other geological events have changed National Geographic's maps before, Valdés notes, from movements in the ground caused by earthquakes to new islands created by volcanoes. The movement experienced in Kathmandu is unlikely to show up in the resolution of the society’s maps, says Valdés, but it remains to be seen for Everest’s height.
The last time Valdés recalled a significant change in a mountain height was in January 2014, when a massive rockfall in New Zealand had reduced the height of Mt. Cook from the previously measured 12,316 feet (3,754 meters) to 12,218 feet (3,724 meters), a difference of 98 feet (30 meters).
The fact that the world’s tallest mountains can move at all “proves how dynamic the planet truly is,” says Valdés.