Craters of the Moon

PART 1: Craters of the Moon National Monument

It was disappointing that almost all trails were closed and being groomed for cross-country skiing.  However, my disappointment did not last long: I lasted just a few seconds in the frigid wind when I tried to hike the one trail open to hikers.  Living in Las Vegas makes one forget how cold it can get in higher latitudes and elevations.  There was a French couple walking with snowshoes, according to Doug Owen,the Park Geologist, who showed us a few movies and made us feel welcome and comfortable in the visitors center.

These are the main craters, cinder cones, volcanos, near the visitors center, some with clearly visible walking paths to their tops:

I learned something new this trip.  I had assumed that plate tectonics was responsible for this series of rather fresh lava domes and basalt fields, but did not realize that there may be two forces at work.  Plate tectonics is moving the continental plate to the southwest and as it moves over the mantle, it moves over a hotspot causing these basaltic eruptions throughout the central Idaho region from southeast east to northeast.  According to this theory, as explained by Doug Owens, the hotspot is at Yellowstone right now making it susceptible to explosive (rhyolitic rather than basaltic, although there can also be explosive basaltic eruptions, usually at the beginning of an eruptive episode).  

Craters of the Moon has a basalt-flow recurrence interval of about 2,000 years and it is now overdue.  With the mantle hotspot now well to the northeast, why would there be another eruption?

There is where I learned something new: as this area gets pulled southwestward it expands and decompresses, and decompressional melting may be the cause of the regular eruptions in this location, and may be the cause of the next eruption!  

I waited, but nothing happened.

In Summer this area is black with fresh basalts, but today it was quite white, but under the white there could be seen fields of basalt broken during cooling, and 'pop ups' of basalt that got twisted up as the field of mixed solid and liquid basalts was flowing.  This false color satellite photo shows the extent of the basalt flows with the Big Lost River valley agricultural area to the left (=north):

This photo shows lichens growing on (colonizing) the edges of the relatively fresh basalts to the north:

Moving south along the highway through the park, basalts are everywhere, including these on the west side of the road:

Looking east across the highway, there are basalts galore, including some pop-ups:

In the distance to the east is Big Southern Butte, the largest and youngest of a series of about a dozen rhyolitic (involving powerful, explosive eruptions) volcanic dome  structures in the area, ranging from ~300,000 to ~600,000 years old according to Doug Owen, the Park Geologist:

Now we move north on the highway and look eastward again.  In the distance in the next photo is Big Southern Butte again:

The trees in the above photo afforded a view northward to the highway to Arco:

To the southwest, a storm was moving in rapidly:

The sun was quickly obscured as we left to turn back to the north:

To the north, it was clear weather!  The next page takes up where this one leaves off, approaching Arco and the Big Lost River Valley:

Go to second Craters of the Moon Page: Big Lost River Valley

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