Dynamic uplift of the Himalaya

Abstract

It has become widely accepted that the Himalaya is the product of collision between the Indian landmass and the Eurasian continent. Holmes¹ conjectured that the Indian Shield was carried northwards by sub-lithospheric mantle flow to cause a double thickening of crust beneath the Himalayas and the Tibetan Plateau. Wager² hypothesized that the extra height of the great peaks of the Himalaya over Tibet was due to isostatic readjustment following the removal of load by intense erosion. Molnar et al.³, relate the uplift to the shear stress on the boundary faults beneath the Himalayas. Relevant data have recently become available from the northern flank of the Himalaya and the Tibet Plateau, of which especially important are: (1) a gravity profile across central Tibet; (2) seismic crustal structures of the region from explosion seismology; (3) seismicity; (4) geothermal activities; (5) geodetic, palaeogeographical, and radiometric data bearing on the uplift rate of the region; and (6) field observation of the surface fault patterns. The combined data-set has imposed strong constraints on theories of the dynamic processes in this region. We summarize here the relevant observations and discuss the results and implications of our model analysis; details of the modelling procedure are given elsewhere⁴.