Knowing our mountainsThe Himalaya is not just mountains, it is the entire watershed from the plateau to the plains
There are many mistaken notions about Nepal and the Himalaya. Nepal is not just mountains — the southern plains make up a quarter of the area and is home to more than half the country’s population.
The general perception is that the highest peaks mark Nepal’s northern border with China in one long chain. Actually, only Makalu, Lhotse, Everest, Cho Oyu, Gauri Shankar up to Phurbi Ghyachu are on the Nepal-China border.
From the north of Kathmandu Valley westwards, Langtang, most of Ganesh, Manaslu, Annapurna, Dhaulagiri, Kanjiroba run diagonally across Nepal. On the other side of these mountains are the trans-Himalayan districts of Humla, Mugu, Dolpo, Mustang and Manang which form 18% of Nepal’s area.
The Himalaya is not one long row of peaks, but is made up of massifs called Himals: for example, Rolwaling Himal, Ganesh Himal, Annapurna Himal or Dhaulagiri Himal. These Himals are separated by rivers that are older than the mountains, and cut through them as they rose after the collision between the Indian and Eurasian plates starting 50 million years ago.
Evidence of this is the Yarlung Tsangpo (Brahmaputra) and the Indus which wander along the Tibetan Plateau until they cut through the mountains. Most of Nepal’s major rivers, including the Karnali, Kali Gandaki, the Marsyangdi, Budi Gandaki, the two Bhote Kosis, Tama Kosi and the Arun originate in glaciers north of the main Himalayan chain
The Kali Gandaki is the deepest scar on the land surface of the earth, flowing at barely 1,400m with two 8,000m massifs of Annapurna and Dhaulagiri towering only 8km apart on either side.
Along its riverbed are ammonites, perfectly preserved fossils of shellfish that lived on the floor of the Tethys Ocean 250 million years ago. Fossilised sea lilies have been found on the yellow limestone on top of Mt Everest — thrusted from the bottom of the ocean to nearly nine kilometres into the edge of the stratosphere.
What makes our mountains so scenic is also why they are seismic. The mountains are still rising at about 1cm a year as India continues to plough under the softer Asian plate — not steadily but in gigantic lurches every few decades. The rock strata move at 20mm every year, and bend with the strain until they snap, causing regular earthquakes.
Himalayan seismologists estimate the tectonic tension building up beneath us, and have calculated that there are 8-9M earthquakes every 500 years or so, with smaller temblors every 100 years along segments of the Himalaya.
The 1934 and 2015 earthquakes have eased the strain in central Nepal somewhat, but in western Nepal there is a ‘seismic gap’ because there has been no megaquake for at least 500 years. An 8.5M earthquake there could lead to surface displacement of 8m or more, causing widespread destruction in Nepal and all over the densely populated north Indian plains.
Aside from the danger of building collapses, an earthquake of this magnitude can cause landslides to block rivers and unleash catastrophic floods of the kind that probably caused the Pokhara Valley to fill up some 600 years ago.
The world’s youngest mountain range is already very fragile, but haphazard infrastructure and settlements without risk assessment makes it even more dangerous. And the climate emergency with its weather extremes adds to the hazards of Himalayan seismicity, including the threat of simultaneous glacial lake outburst floods.
We need to know our mountains, our own survival depends on it. Nepal’s planners and government ought to factor in earthquake and climate risks in future development. The mountains will seek their revenge if we mistreat them. Wilful ignorance, greed and incompetent implementation are sure to invite disaster.
The Himalaya is not just a mountain range. It is the entire watershed from the Tibetan Plateau, though the Himals, Mahabharat and Chure foothills to the Tarai. This is the water tower of Asia, it stores ice and groundwater not just for Nepal but for hundreds of millions of people downstream.
It is Nepal’s duty to protect the Himalaya not just from and for ourselves, but for humans and other life forms we share this planet with.