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Plate boundary and mountain formation

Short answer

Plate boundaries are divergent (apart, new crust), convergent (together, subduction/collision) and transform (slide). Mountains form mainly at convergent boundaries where thick geosynclinal sediments are compressed, folded, faulted and uplifted, then shaped by erosion.

Describe plate boundaries. How is a mountain formed?

Plate boundaries

The lithospheric plates meet at three types of boundary.

  • Divergent: plates move apart; new crust forms (mid-ocean ridges, rift valleys).
  • Convergent: plates move together; subduction or collision (trenches, island arcs, fold mountains).
  • Transform: plates slide past each other (San Andreas Fault).

Formation of mountains

Mountains are mainly formed at convergent boundaries.

  1. Thick sediments collect in a long, sinking trough (geosyncline) at a plate margin.
  2. Plates move together and compress the sediments.
  3. The layers are folded, faulted and thrust upwards, with metamorphism and igneous intrusion.
  4. Uplift and erosion then shape the range.

Examples: Himalaya (continent-continent collision), Andes (ocean-continent subduction). Other mountains are formed by volcanism (Fuji) and block faulting.

✓ Answer checked by Claude Opus 5.5 (high effort)

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