Nature · Earth Science
Where the planet’s inner heat breaks the surface
Geysers, hot springs and fumaroles are the visible breath of Earth’s internal heat. Wherever groundwater seeps down close to hot rock or a shallow magma chamber, it is heated far above boiling and forced back to the surface — sometimes gently as a steaming pool, sometimes violently as a towering jet of scalding water and steam.
Rain and snowmelt sink through fractured rock until they meet ground heated by magma or hot crust. Trapped in a plumbing system of narrow channels, the water superheats under pressure. When a bubble of steam finally clears a constriction, the pressure drops, the whole column flashes to steam and erupts — then the system refills and the cycle repeats.
Groundwater descends, superheats near a magma chamber, and rockets up a constricted conduit — the engine behind every eruption.
Bursting from a pool in wild sprays
Fountain geysers erupt through a pool, so the water sprays out in dramatic, multi-directional bursts rather than a single column. They are often the most spectacular and unpredictable of all geysers.
A steady jet from a mineral nozzle
Cone geysers erupt through a raised nozzle of geyserite deposited over centuries, focusing the water into a tall, steady column. Old Faithful is the world’s most famous example.
Gently steaming pools of heated water
Where hot water reaches the surface without a constriction to trap pressure, it simply pools and steams. Thermophilic bacteria paint many springs in brilliant rings of orange, green and blue.
Steam vents and bubbling clay
Where there is heat but little water, escaping steam and gas form fumaroles; where acidic steam dissolves surrounding rock into clay, it bubbles as a mud pot. Both mark the driest, most acidic parts of a geothermal field.