Final answer:
The Archaea that live in extremely hot environments such as hot springs and around volcanoes are called thermophiles. They are a type of extremophiles that thrive in conditions that are hostile to most life forms.
Step-by-step explanation:
The Archaea that live in hot springs, geysers, submarine thermal vents, and around volcanoes are known as thermophiles. These organisms have adapted to thrive in extremely hot environments, some in temperatures nearing 100°C, which is the boiling point of water. Thermophiles are a type of extremophile, organisms that love extreme conditions, which often inhabit environments reminiscent of early Earth, suggesting that they might have evolved very early in Earth's history.
Within the domain Archaea, which is as diverse as domain Bacteria, extremophiles can live in a variety of harsh conditions, including extreme heat and salinity. For instance, another type of extremophiles within the Archaea domain are halophiles, which live in highly saline environments like the Great Salt Lake in Utah and the Dead Sea. These Archaea perform vital functions in ecosystems, such as playing roles in the carbon and nitrogen cycles, and they can be found in great abundance in the oceans.