Mount Washburn

A hike to the top of Mount Washburn was our main activity for our first full day in Yellowstone.  It's a 6 mile round trip, about 1300 feet of elevation gain, and provides incredible views of the Yellowstone area.

Wildflowers adorned the trail much of the way.

We encountered snow across the trail at about 10,000 feet.  The trail was once a blacktop road, but it has been closed to vehicular traffic.  Only hikers are allowed. 
The terrain near the top of Mount Washburn is rock formed from lava, the result of volcanic activity over millions of years.  The most recent lava eruption was about 70,000 years ago.

The fire tower observation room looks out on the scene above, with Mount Sheridan (10,300 ft) to the left (35 miles away) and the Teton Range (13,700 at the highest point - 75 miles away) barely visible to the right.  The observation room is a favorite lunch break spot for hikers.  A spotter scope and lots of windows allow for good scenery and wildlife viewing.

The top floor of the tower is a ranger's living quarters.  What a great 360 view! 

Looking south toward Yellowstone Lake, you can view a huge caldera (a depression in the earth) caused by a super volcano that erupted about 640,000 years ago, following which the earth's crust collapsed into the emptied magma chamber.  The rim of the caldera is defined by Mount Washburn on the northern end and Mount Sheridan on the south.  You can also see the chasm through which the Yellowstone River flows.  This is called the Grand Canyon of the Yellowstone.

Hotspots remain beneath the caldera, and these are responsible for Yellowstone's geothermal activity (about 50% of the world's geothermal activity occurs here) visibly apparent through  the many geysers and mud pots.  1000 to 2000 earthquakes occur every year in Yellowstone, but most are less than magnitude 3 intensity.   (The photo above came from Wikipedia.)

Here's a photo from the observation tower showing the Teton Range (10X zoom photo) 75 miles away.  We were fortunate to have such a clear viewing day.
Mount Washburn was named after Henry D. Washburn, who led an expedition into Yellowstone in 1870.