Yellowstone National Park's Old Faithful geyser can now be viewed online via a high-definition (HD) streaming webcam.
Geysers are rare natural fountains of hot water. Most of Yellowstone's geysers barely reach ten feet in height, but Old Faithful is one of six that can erupt 100 feet or higher.
Old Faithful's webcam page indicates when eruptions are predicted to happen (about every 45 to 90 minutes), so you can be sure to catch a glimpse of it as it releases water and steam. You may also see eruptions from neighboring geysers, as pictured below.
Yellowstone has the world's largest concentration of geysers. While legendary Old Faithful is neither the largest nor the most regular of Yellowstone's 300 active geysers, it erupts more frequently than any of the other large geysers in the park.
Watch Yellowstone's video "Why is Old Faithful Famous?":
Old Faithful is a cone-shaped geyser but there are many other types, each with their own unique way of projecting boiling water from beneath the surface. The geysers at Yellowstone represent only three percent of its 10,000 geothermal features, which include the picturesque Grand Prismatic Spring.
The animation below explains how geysers work:
Photo and animation courtesy of NPS.