Definition of underthrust in English:


Pronunciation /ˌəndərˈTHrəst/ /ˌəndərˈθrəst/

transitive verbunderthrust

[with object]Geology
  • 1Force (a crustal plate or other body of rock) beneath another plate or block.

    ‘the Farallon plate was being underthrust beneath the North American plate’
    • ‘this sediment may be deformed by the underthrusting’
    • ‘Patterns of this type can be readily explained by accretionary tectonism, whereby a packet of sediment accreted at the toe of the prism is underthrust and buried beneath an overburden of older strata.’
    • ‘Here the Papua New Guinea continental crust appears to be underthrusting the adjacent marginal basin and obduction of the ophiolite is occurring in an uphill direction.’
    • ‘The tensional stresses in the uplift can be relaxed by, for example, underthrusting in a subduction zone, or contraction in surrounding regions.’
    1. 1.1Be forced underneath (another plate or block)
      • ‘plate X is underthrusting plate Y in a northeast direction’


  • An instance of one plate or block being forced underneath another.

    ‘the westward underthrust of the Pacific Ocean plate’
    • ‘We suggest that because the upper portion of underthrust sections lacked any thick, water-saturated clastic deposits this did not favour the formation of melanges.’