A hot spring is a spring that is produced when geothermally heated groundwater emerges from the Earth's crust. Some hot springs have waters that are cool enough for bathing, but in volcanic areas water may come into contact with rock that has been heated by magma. These hot springs sometimes produce water that is hot enough to kill animals that enter them. In non-volcanic areas, water can still be heated geothermally because the temperature of rocks within the Earth increases with depth, and if water percolates deeply enough into the crust, it can gain heat from these rocks and then flow to the surface.
A geyser is a rare geothermal feature. When a large amount of groundwater that is trapped in underground cavities in a volcanic area is heated by the presence of magma and magma heated rocks, the extreme heat turns the water into steam very quickly. This causes sudden and immense pressure, which forces huge quantities of water up out of the ground, producing stunning sprays of water shooting up to hundreds of feet into the air. This type of eruption can happen regularly or in cycles.
(Continue Reading from The National Parks Service)
The Complex Dynamics of Geyser Eruption - from The United States Geological Survey
The Science Behind Yellowstone’s Rainbow Hot Spring - from The Smithsonian Magazine
Thermal Springs Viewer - from The National Centers for Environmental Information
Geysers - from National Geographic
How are Hot Springs Formed? - from World Atlas
People have been visiting hot springs and enjoying watching geysers erupt for centuries. United States citizens looking to see hot springs and geysers for themselves need look no further than Yellowstone National Park. Yellowstone is one of the most famous areas of hot springs and geysers in the world, boasting more than half the known geysers on the planet. (Continue Reading from The Encyclopedia Britannica)