Yellowstone National Park – the United States’ first such park – is also home to more than 10,000 hydrothermal features, including 300 geysers, which result from volcanic activity. They occur when magma or very hot rocks deep in the earth heat groundwater. A geyser’s spout of steam and hot water takes place when the pressure of the near-boiling underground water is released. The entire Yellowstone region is volcanically and seismically active, and is known as a “supervolcano.” This map illustrates Yellowstone’s Upper Geyser Basin – home to the famous Old Faithful geyser – just four years after the park was established.
IIIF Manifest