How I Spent My Summer--Travelogue: Part VI

Trip #6--R Mountain
Out west of Rexburg, Idaho there is a pair of volcanoes that dominate the skyline.  They are called the "Menan Buttes".  The north butte is the tallest and most of it sits on BLM land.  The south butte is privately owned and a family farms in the crater.  The north butte is referred to as "R Mountain" because of a big white R that is painted on it.  Here in the west, it used to be traditional to paint a big letter on the side of a mountain to indicate something about the area.  The R was either for Rexburg or Ricks College, I was never sure which.  I believe it was for Ricks College because students from there are the ones who always painted the R.  When I was a kid, every year at Ricks College homecoming, students would hike up to the R, cover it with kerosene soaked burlap bags and light it at nightfall.  It would burn for an hour or so and was always a cool thing.  Since Ricks College changed to BYU-Idaho the R has fallen into disrepair and is no longer being maintained.



The north butte, or R Mountain.  The R is barely visible now

These two volcanoes are unique and are studied by vulcanologists from all over the world.  First, they are among the largest tuff cones in the world, and second they erupted through the Snake River and the river gravels.  These are the only tuff cones to do so in North America, so combining that with their size, these are very special cones.  A xenolith is a rock with a different origin than the volcanic material embedded in the tuff.  These volcanoes have xenoliths that are both lava rocks from previous flows and river rocks from the river gravel. 

When I was in the eighth grade, our geology class climbed the north butte for a field trip.  I may have climbed it one other time but I don't remember.  I decided to take my sons up the R this summer and I'm glad I did.  It was a fun hike and we had a great time doing it.  When I climbed it before, I went up the east face trail.  That trail has been closed and now there are two remaining trails on the south side and the west side.  We chose to climb the west face.



My sons at the trailhead on the west face of R Mountain

The trail is well maintained and the first two or three hundred yards is sand and gravel.  As the trail rises, it alternates between dirt, sand, and rock.  The landscape is dominated by large sagebrush and juniper trees and the further up the mountain you go, bizarre rocky outcroppings that look like they belong in a sci-fi movie.  The view out over the valley is breathtaking as well.  To the northwest you can see the remnants of multiple lava flowsand evidence of collapsed lava tubes.



Sagebrush and Junipers

Lava flows and collapsed lava tubes

Rocky outcropping

Toward the summit there were many small caves and overhangs.  In one we found evidence of animals using it for shelter, as there were twigs and bark and leaves gathered together in what looked like a den.



Random cave near the summit

The R Mountain is climbed daily and frequently and is well maintained.  The BLM wishes people to stay on the trail up the face because native plants have been trampled and erosion has ensued, so in places they have built rail fences along the trail to keep people from sensitive areas.  At the summit, the climb becomes steeper and they have placed a chain railing there to assist climbers.  Once on the rim, the view is really incredible.  To the East is the city of Rexburg, to the south is the second butte, to the west is the desert and farmland and to the north is the Island Park Caldera.  At any point on the rim, the crater is also visible.  There are a few trails up on the rim.  One trail follows the rim all the way around and another cuts through the crater.  We only had time to do about half the rim trail and then cut through the crater as we had a Boy Scout court of honor to attend that night.  We chose to do the south rim.



The crater from the west rim

Veiw to the west from the rim

The south rim has many strange rock formations and appears very alien and rugged.  Xenoliths are abundant.  There are interpretive signs in several places on the rim that talk about the geology, biology, ecology, and botany of the buttes.  It all makes for an interesting hike.  We wildcatted around the rocks of the south rim for awhile and explored some of the formations before we found the crater trail and headed for home.  We found a basin or depression that appeared to have water in it in the spring and after rainclouds.  We imagined that this would be a place where some of the lizards, birds and other animals that populate the buttes would come to drink.  This was another great day.



Basin

Rock formations on south rim

Strange rock formation

A xenolith

Alien landscape