How does magma transfer heat to underground groundwater?

Magma transfers heat to underground groundwater primarily through the process of conduction. As magma moves upward from deep within the Earth to depths of only a few kilometers, it brings intense heat—reaching temperatures near 1,200 °C (2,200 °F)—into close proximity with groundwater reservoirs.1

Once the groundwater absorbs this thermal energy, it begins to circulate through the subsurface via convection. In this process, the heated water becomes less dense and rises, while cooler water sinks to take its place, establishing a continuous cycle that distributes heat and forms large underground reservoirs of hot water and steam. This natural mechanism is essential for concentrating Earth's internal heat, allowing it to be tapped for geothermal power or observed at the surface in the form of hot springs and geysers.12