Yellowstone National Park celebrated its sesquicentennial on March 1st but the party is ongoing throughout 2022. Not just the first national park in the United States, YNP was the first in the world.

It sits on top of an active volcano - a super volcano - which is one of the largest calderas on earth at 45x30 miles. That's what powers the park's 10,000+ hydrothermal features, more than 500 of which are active geysers (that's more than half of all the geysers on the planet).

Especially when walking through the geyser fields, you can feel the heat and see the energy. It's obvious something is going on beneath your feet - but you may not realize just how close you are to the action. Magma is very near the surface in greater Yellowstone.

There have been three super-eruptions over the past two million years, each of which created a caldera. The third and most recent super-eruption is responsible for the caldera we're familiar with today. As the volume of magma and hydrothermal fluids fluctuates and/or as magma moves between the two chambers which lie beneath the park, the caldera floor lifts, tilts, subsides, and shifts.

If you're wondering how a super-eruption differs from a "garden variety" volcanic eruption, it's more powerful by many magnitudes. Catastrophic isn't really a descriptive enough adjective but it'll have to do. Yellowstone's first super-eruption ejected more than 6,000 times as much volcanic material as did Mount St. Helens in 1980, covering nearly 5800 square miles with ash.

The three super-eruptions combined expelled enough ash and lava to fill the Grand Canyon.

All this heat and movement just beneath the surface makes Yellowstone prone to earthquakes. Lots of them. It's one of the most seismically active areas in the country. (There were more than 1,000 last July.)

As far as hydrothermal features are concerned, Old Faithful snags the lion's share of attention but some of my favorites are found elsewhere. Mammoth Hot Springs is one example.

These beautiful, otherworldly "fountains" appear almost as if they're waterfalls which have been frozen in action and painted with colorful stripes.

Water trickles from some; others are dry. The distribution of water changes as the magmatic system underground shifts.

The terraces were created by this thermal water: rising through the limestone, it releases carbon dioxide when it reaches the surface and deposits calcium carbonate, which in turn creates travertine. Voila!

We can thank heat-loving bacteria for the stunning paint job which decorates the terraces. These are the same thermophiles which populate other hydrothermal features you'll see elsewhere in the park.

If you enjoy abstract photography, you'll find plenty of potential subject matter in Yellowstone's hot springs and bacterial mats.

I made the images below at the mat near Grand Prismatic Spring. Different thermophiles live at various specific temperatures; that's what creates the variety of colors.

Geysers don't always have to boast super-sized eruptions to be interesting (at least in my book). I have a soft spot for Clepsydra, located between the Midway and Lower Geyser Basins. It doesn't toss spray hundreds of feet into the sky but it's showy in its own understated way. Since the late 1950s it has erupted almost continuously. I've seen it in all four seasons and stop by for a visit every time I'm in that area of the park.

 In Yellowstone, the fire is right there, just beneath your feet. Magnificent.

 Did You Know?

There's more to the park than geysers, mudpots and hot springs.

• Yellowstone boasts more than 900 miles of hiking trails

• It's home to the largest high-elevation lake in North America (Yellowstone Lake is 7,733 feet above sea level)

• Its ecosystem is nearly intact - meaning the plants and animals you'll find there are essentially the same now as before humans arrived

• Part of Yellowstone is located in Idaho

• It's home to the largest concentration of wildlife in the Lower 48

• It's the only place in the U.S. where bison have lived continuously since prehistoric times

Happy Birthday to the granddaddy of them all.