Many people don’t realize that what’s driving all the geyser activity in Yellowstone is a big volcano. In fact, everything you see in Yellowstone –from the geysers and hot springs, to plants and animals to even the abundance of waterfalls and frequency of fires—is because the park sits atop one of the world’s largest volcanoes.
The fact that the Yellowstone volcano is in the middle of a continent makes it unique and helps to generate rare plentiful geyser activity. The volcano or hot spot not only provides the heat and the right plumbing system needed for geysers, but it also accounts for almost everything else in Yellowstone.
As the volcano’s magma domed up the ground surface of the entire region it caused our high elevation climate and weather. The lava that oozed out, cooled and hardened into rock, establishing the soil types. Climate and soils determine plant varieties which, in turn influence the wildlife because particular animals eat specific plants and other animals prey on those animals, and so on.
The high Yellowstone Plateau is frequently struck by lightning as storms pass through, sparking fires while the resident plant communities correlate to the frequency and intensity of the fires. The volcanic crater/caldera and successive lava flows have broken up the high plateau creating sheer faces that drop to lower areas. The high areas catch abundant snow and as it melts, streams run off and down the sheer slopes creating myriad waterfalls. The geyser basins, rivers and lakes are located between the lava flows.
Geysers, wildlife, fire, lakes, waterfalls…Though volcanoes are often considered destructive, the Yellowstone volcano is, in essence, responsible for the whole natural network here. It’s what makes Yellowstone Yellowstone.
So you’ve heard about the Yellowstone volcano. But where is it? It’s the shear size of the Yellowstone volcano that makes it so hard to discern. Most people look for a cone-shaped mountain when you say “volcano.” Yellowstone has several of those. But the Yellowstone volcano is much larger than that. The whole area is a massive high plain domed upward due to the heat of magma below. That accounts for the park’s high elevation which averages 8000 feet above sea level.
The Yellowstone volcano has erupted many times over millions of years but the last three eruptions left calderas or craters in the park. The last eruption over 640,000 years ago left a caldera 30 by 45 miles wide.
Lava continued to seep out of the volcano after the last eruption and some of those lava flows filled in portions of the caldera so it’s not as deep as it once was. Much of the park is actually in the crater and the large size makes it difficult to tell you are in the crater of a big volcano.
There are a few places in the park where you can see the caldera—Gibbon Falls, Washburn Hot Springs Overlook, from the top of Mount Washburn. It is probably best seen from outer space. From that vantage point, you would actually see that the Yellowstone volcano or hotspot is responsible for a series of calderas that stretch from the park, south and west to Nevada.
The hotspot or magma chamber below ground has erupted periodically over the last 16 million years as the continental plate has slowly drifted over the top of it, creating a string of volcanic eruptions and calderas.
Yellowstone sits atop the magma chamber today and though it may be difficult to conceive the volcano, the plethora of hot springs and geysers are a good reminder that it is there, just under our feet.
You cannot fish from Fishing Bridge. Until 1973 this was a very popular fishing location since the bridge crossed the Yellowstone River above a cutthroat trout spawning area. It is now a popular place to observe fish.