Kathleen's Window: Craters of the Moon National Monument

Thursday, September 11, 2014

Craters of the Moon National Monument

Thursday, September 4, 2014

Lewis Lake campground receded in the rear view mirror as we left Yellowstone and drove toward Grand Teton National Park. The temperature was in the forties, and we just weren't feeling it for a hike. Turning into the visitor center we realized that the park would be crowded too, so we decided to just drive through it and continue on towards Idaho.

Looking at the Grand Tetons across Jackson Lake from the Colter Bay Marina

Driving down the scenic road toward Jackson

Beautiful exposure of a diorite dike (vertical, dark rock intrusion) at the top of the mountain.

We drove through downtown Jackson, hoping to possibly find street parking to get lunch and explore, but, it too was crowded and we drove west towards Idaho. Leaving Jackson we joined the Snake River, and then crossed into Idaho at the Palisades Reservoir. A quick stop for lunch at Alpine, and we were on our way west through the arid grasslands toward Idaho Falls, and then to the town of Arco, which was the first town in the U.S. to have electricity powered by the first nuclear power plant, just outside of town. That was in the 50's!

Antler arch in Jackson town center

Looking across the Snake River Plain at the surrounding mountains

After Arco the desert gave way to lava flows as we entered the Craters of the Moon National Monument. We found a campsite in the small barren campground with sites scattered among the lava piles. Greg tried to sign up for three nights, but they only allowed campers to sign up a night at a time. We soon learned why. The black rock soaks up an extraordinary amount of heat. We were kept warmer than the surrounding area at night, as the rocks gave off the heat stored up during the day. Summer must be brutal. In the past, they probably had lots of campers asking for refunds! We wound up staying three nights. Hot, dry days, and comfortable nights, $5 a night, and an unusual and spectacular landscape kept us there. Greg was able to ride the paved park roads every day on his bike, and we hiked the trails.

Our campsite in the lava and cinders

Happy hour on our campsite patio atop a 20-foot high pressure ridge

Greg's geology commentary - Craters of the Moon National Monument preserves an area of volcanic formations including many square miles of lava flows and their source vents. The lava flows erupted about 2,000 years ago, leaving flows ranging from smooth-looking pahoehoe to rough, blocky a'a and frothy scoria cinders. Vent structures include large cinder cones, smaller spatter cones and pressure ridges, and a variety of intact and collapsed lava tubes, some over 50 feet in diameter. The monument comprises the northern section of the Great Rift, which is a linear zone of volcanic vents and pull-apart crevasses from which lava flows flooded the surrounding desert landscape. The Great Rift is a clear example of recent volcanic activity associated with Basin And Range tectonic stretching and thinning of the earth's crust within the already-thin crust of the Snake River Plain. Southeast of Craters of the Moon, lava drained out of the vents while still hot, leaving rifts open to 800 feet deep. Unfortunately, we did not get to see these interesting fractures because they were 30 to 40 miles away down primitive desert roads that are not RV friendly.

The photos below give you a sample of this wild landscape. Enjoy!