THE FOURTH IN AN OCCASIONAL SERIES OF EARTH PHENOMENA

This, the Iargest continental earthquake of the 20th Century, occurred on a low‐angle detachment at the eastern end of the Himalayan mountain arc. Great earthquakes in this region are fundamental forces of erosion: above the c.300X150 km‐long fault rupture, in the steep‐sided valley‐tributaries of the upper Brahmaputra, landslides covered about one third (15, 000 km 2 ) of the surface comprising an estimated 5X10 10 m 3 of debris, 30 times the volume carried annually by the whole Brahmaputra River. Two English plant‐hunters, Jean and Frank Kingdon‐Ward, with their Assam guides were based in the upper Lohit Valley, just over the Tibetan border with Assam, waiting for an opportunity to ascend to the Alpine pastures.