An area of the Himalayan Mountains has actually dropped in height by around one metre following the recent, devastating earthquake that affected much of Nepal, according to scientists. They think that the drop will slowly be balanced back out however by tectonic activity.
Figures
The world’s highest mountain, Everest, has yet to be analysed and even then, there is still debate over exactly how tall the mountain is.
The main area to see a drop is a length of mountains from 80-100km in the Langtang Himal, northwest of the capital city of Kathmandu, according to geologists with the United States Geological Survey (USGS).
This area is where many of the locals and trekkers are still missing in the aftermath of the earthquake, particularly following the avalanches and landslides that were triggered by the 7.8 magnitude movement of the Earth on 25th April.
Scientists also think that some of the other Himalayan peaks, including the Ganesh Himal to the west of the Langtang range, could also have seen a decrease in height. Satellite images have so far been focused mainly on central Nepal, the area hit hardest by the earthquake, while Everest is to the east of this area.
Scientists added that to check if the height of Everest had altered would need to be confirmed with ground surveys or an airborne mission in addition to satellite data. So far, the data provided by the Senteinel-1a satellite has shown an area north of Kathmandu that has subsided by around 1.5m.
Changes
Scientists with the German Aerospace Centre (DLR) compared images of the region before and after the quake. The positive value received from these satellite images shows that the area around the Langtang region is now further away from the satellite, meaning it is lower than before.
However, the assessment is for a general area, rather than showing that a specific mountain is a specific amount smaller than before. Assessments say that the area has dropped by 0.7m up to 1.5m.
The same study showed that the area around Kathmandu, to the south of the Himalayas, has lifted up after the quake. Their position in relative to the satellite is showing as being closer to it so they have been raised by the movement of the Earth.
Scientists also add that this drop and uplift is a normal part of an earthquake of this scale.
Collision
What has happened is that the fault running beneath Kathmandu has slipped and moved over the top of the part of the crust to the south, while the northern end gets stretch, says Tim Wright, a professor of satellite geodesy at the University of Leeds.
Where it is squashed, the land lifts up but when it is stretched, the land falls downwards. The biggest amount of slip on the fault was just north of the capital so the mountains north of this have seen the most drop off.
Normally, the Himalayas rise due to the collision between the Indian and Eurasian tectonic plates but in the event of a major earthquake such as this one, the process is reversed.
