Yellowstone National Park 4

(9/4) Mammoth Hot Springs.

Today we explored Mammoth Hot Springs in the northwestern section of this huge park. The springs here look different from those around Old Faithful, and for a reason.

Although the entire Yellowstone region was once covered by an inland sea, no limestone is now found in the central area of the park, where Old Faithful is found. The limestone must have been there once, but is gone now-- blasted away in huge volcanic explosions during the past 2 million years. The huge crater left by these explosions, known as the Yellowstone Caldera, was later filled in by silica-rich lava flows. Superheated water comes to the surface through cracks in the lava rock to form the geysers and hot springs in the Old Faithful area.

The Mammoth Hot Springs area lies outside the Yellowstone Caldera and still has limestone rock layers. Here, the ground water that comes to the surface through these layers is laden with calcium carbonate, not silica. As hot water surges out of these springs and flows downhill, it coats the hillside with calcium carbonate. The shining white hillside at Mammoth is visible from miles away.

Up close, the slopes below the springs are seen as a series of beautiful terraces.

Where the springs are still active, each terrace is a water-filled pool with beautifully decorated walls.

We were fascinated by the slope below a small spring, which had dozens of tiny terraces.

On our way back to the cabin, we had a fortunate wildlife sighting. A group of Bighorn Sheep was clustered high on a hillside above the road.