640,000 years ago a massive volcanic explosion formed a caldera 45 miles long by 28 miles wide and over a half-mile deep – and that was the third cataclysmic event that helped form what we know as Yellowstone National Park today.

The purple circle in the middle of the map shows the edges of the enormous caldera, and underneath it (as well as the rest of the park), the earth’s roiling super-heated magma comes close to the surface causing fumeroles, geysers, mud pots, and hot springs. The earth seems angry as it steams and erupts all around the Yellowstone landscape.

The chilly air meeting the hot steam at the Grand Prismatic Spring made it impossible to see the clear blue water and rainbow colors of the heat-loving bacteria surrounding it, but I loved the mysterious feeling of walking through the billowing clouds.

Runoff from the Grand Prismatic Spring makes these vivid rust-colored streams…

…and other hot springs had similar runoff streams, all in eye-popping colors…

…originating from impossibly blue pools.

Old Faithful didn’t disappoint with a good sized eruption…

…and we were awed by the Grand Canyon of the Yellowstone River – this is the more dramatic lower falls.

The deep canyon is cut by water flowing along the Yellowstone River from the 136 square miles of Yellowstone Lake.

Of course we encountered a number of wildlife sightings in our explorations around the park. Trumpeter swans…

…adorable chipmunks…

…massive bison…

…and a nice fat grizzly bear foraging before winter.

All the while, sulfuric acid dissolves rock to create plopping, spurting mud pots…

…and water finds its way through the Earth’s thin crust to create steaming pools of scalding water. There’s a lot of beauty in the many ways the angry earth makes itself known here.

All the while, delicate beauty is all around – you just have to look past the steam to see it!

We had so many plans for our precious days in Yellowstone and the Grand Tetons just to the south, but a big winter storm with snow and frigid temps was heading our way. The safe bet was to get out of its path ahead of time, so sadly we had to cut our visit short and head for better weather in Salt Lake City.