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Elements of a geothermal system

A schematic showing how groundwater is warmed.

Groundwater flows down to depths of a few kilometres, gets heated up and rises to the surface by convection.

  • Heat source: Underlying the system at depth is hot magma.
  • Rising water: Groundwater near the magma becomes heated and more buoyant than the surrounding colder waters and rises through pathways that lead to the surface (hot water is also less viscous than cold water).
  • Hot water plume: The rising water is discharged at the surface through hot springs and steaming ground.
  • Interaction: The rising fluids interact chemically with the surrounding rocks and their temperature is moderated by mixing with cooler water and by local boiling.
  • Counter flow: The upward flow of hot water from depth creates a downward counter-flow in the surrounding area so the surrounding cold water moves downwards.
  • Convection system: The movement of the two types of water create a circulating convection system that is a very efficient way to transfer heat.