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Rugged Coasts

Rugged Coasts. Image: GNS Science, Julian Thomson.

Image: GNS Science, Julian Thomson.

New Zealand has over 15,000 kilometres of coastline, shaped by powerful processes of erosion and sedimentation due to wind and waves.

Rising sea levels after the last ice age stabilised about 7000 years ago. This means that all the world’s coastlines are relatively young geologically.

How are our coastal landforms created?

  • Coastal uplift – Uplifting of beaches and flat marine platforms that originated at sea level.
  • Deposition – Rivers and ocean currents move sediments, such as pebbles and sand, to build up spits, tombolas and sandbars. Wind creates the sand dunes.
  • Coastal erosion – Cliffs are undercut and beach/dune sediments are removed by currents, waves and tides.
  • Sinking basins and valleys – Ancient inland hills and river valleys are drowned by rising sea levels and land subsidence.

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