“The Himalaya is still rising.” Expand this statement and describe the processes involved in it with suitable sketches and examples.

“The Himalaya is still rising.” Expand this statement and describe the processes involved in it with suitable sketches and examples. (2025)

  • The statement means that the India–Eurasia collision, which began in the Palaeocene–Eocene, has not ended: the Indian plate still converges with Eurasia, and the range is still being shortened, thickened and pushed up today.
  • “Rising” needs care. Philip England and Peter Molnar separated three things: rock uplift (rock moving up), exhumation (erosion removing the cover) and surface uplift (mean ground level going up). The Himalaya shows abundant rock uplift; whether its mean height still grows is debated, because erosion removes rock almost as fast as tectonics raises it.
Himalayan Orogeny Collision Diagram

Evidence that uplift continues

  • Geodesy: GPS shows India converging with Eurasia at roughly 4–5 cm a year; about 18–20 mm a year of this is absorbed across the Nepal Himalaya alone (Thomas Ader, Jean-Philippe Avouac and colleagues, 2012).
  • Seismicity: great earthquakes — Bihar–Nepal 1934, Assam 1950, Gorkha 2015 — release strain on the same fault that builds the range.
  • Geomorphic signals: uplifted and tilted river terraces along the Siwalik front; deep, young gorges cut by antecedent rivers (Indus, Sutlej, Arun, Brahmaputra) that kept pace with the rising range; rejuvenated youthful valleys.
  • Tibetan lakes stand ringed by gravel terraces tens of metres above present water level, and Siwalik-type fossils occur on the now-high plateau — both read classically as evidence of recent uplift.

Process 1 — Underthrusting and crustal shortening

  • India slides northward beneath the range along one gently dipping master fault, the Main Himalayan Thrust (MHT) — a décollement from which the major thrusts branch upward:
    • Main Central Thrust (MCT) carries the Greater Himalayan crystallines over the Lesser Himalaya;
    • Main Boundary Thrust (MBT) carries the Lesser Himalaya over the Siwaliks;
    • Himalayan Frontal Thrust (HFT) — the youngest — folds and lifts the Siwalik foreland sediments.
  • Deformation has migrated southward with time, so the Siwaliks are the newest part of the mountain wedge; this is shortening and crustal thickening (crust about twice normal thickness) in action.
  • The South Tibetan Detachment at the top of the Greater Himalaya is a normal fault: the high wedge extends at its crest even while thrusting below lifts it.
Cross-section of the Himalaya showing the Main Himalayan Thrust with HFT, MBT, MCT and STD, India underthrusting, and 2015 Gorkha uplift and subsidence.

Process 2 — The earthquake cycle

  • For centuries the shallow MHT stays locked; India keeps moving, so the overriding wedge bends, and the high range creeps upward between earthquakes.
  • A great earthquake then releases the strain. The 2015 Gorkha earthquake (Mw 7.8) raised the Kathmandu Basin by about 1 m but let the high Himalaya farther north subside by about 0.6 m (John R. Elliott, Jean-Philippe Avouac and colleagues, 2016).
  • Their reading: the high peaks grow mainly between earthquakes, as slip continues on the deeper, steeper ramp of the MHT — “still rising” is a long-run sum of slow rise and sudden drops.
  • Earthquakes that break the surface on the HFT lift Siwalik anticlines in single steps, leaving uplifted terraces as their record.

Process 3 — Isostasy and erosion

  • The range floats on a thick crustal root (Airy-type compensation). When rivers and glaciers strip mass away, the root rebounds and lifts the peaks — erosion lowers valleys but can raise summits.
  • Tectonic aneurysm: at the Nanga Parbat and Namche Barwa syntaxes, intense gorge incision weakens the crust and focuses very rapid rock uplift (Peter K. Zeitler and colleagues, 2001); exhumation near Namche Barwa accelerated again in the last ~100,000 years (Rong Yang, Frédéric Herman and colleagues, 2021).
  • Everest example (live debate):
    • Xu Han, Jin-Gen Dai, Matthew Fox and colleagues (2024) argued that the Arun River captured a large Tibetan headwater about 89,000 years ago; the extra incision unloaded the crust, and isostatic rebound explains ~15–50 m of Everest’s anomalous height.
    • Joel S. Leonard and Kelin X. Whipple (2026) replied that the Arun’s steep, disequilibrium profile is better explained by orographic rainfall than by river piracy.
    • The rebound mechanism is sound physics; the specific capture trigger is unproven.

Limits to “rising”

  • Gravitational spreading of thickened crust — the STD and north–south grabens such as the Thakkhola (Mustang) and those of southern Tibet — shows the orogen also collapses under its own weight.
  • Measured uplift is millimetres a year, not centimetres; much of it is cancelled by erosion, so parts of the range may be near a steady state of rock uplift balanced by denudation.
  • Judgement: the statement is sound — continuing convergence on the MHT, the earthquake cycle and isostatic rebound keep lifting Himalayan rock today — but the precise claim is that rock uplift outpaces or matches erosion, not that every peak grows steadily; the Everest river-capture debate shows that even the cause of a single summit’s height is still being contested.