15 October 2016, Saturday
There is actually a bit of sunshine trying to peek through the ragged clouds this morning. After cobbling together some breakfast in our room we begin our drive to the national monument. We stop on the way out of town at a historic marker which notes that Arco, in 1955, was the first town in the US and in the free world to be lit by atomic power. As we returned home from dinner last night we had noticed the conning tower of the submarine USS Hawkbill rising from the ground next to the road. It was donated to the town by the Naval Historical Society because of Arco’s role as the site where nuclear propulsion for submarines began.
O and I continue west on Rt 20 towards Craters of the Moon to learn more about the area’s volcanic past. The lava flows of this region formed between 15,000 and 2,000 years ago, quite recently geologically speaking. The hot spot in the earth’s mantle that currently underlies Yellowstone was responsible for the volcanic activity here, as the North American Plate drifted west over the stationary hot spot. Lava erupted from rifts that developed as earth’s crust stretched and cracked. We learn there are cinder cones and splatter cones here. We note there are two main types of lava: Pahoehoe (pa-hoy-hoy is the pronunciation, from Hawaiian meaning rope-like) and A’a (ah-ah, also from Hawaiian, meaning hard on the feet.) The pahoehoe is the ropey, wrinkled lava, while a’a is the sharp broken lava.
The volcanic activity that occurred here was violent enough to create immense calderas that swallowed mountains. The calderas were subsequently covered in layers of lava. After our mini geology course at the visitor center we begin our exploration of this eerie landscape. We walk amidst lava flows.
We climb to the top of a cinder cone from which we can see a distant kipuka, an area, usually raised, whose vegetation is protected by surrounding lava flows. These undisturbed areas are used to study the original plant life that existed before interference by humans. We walk the path up the side of a splatter cone and then follow another trail up the side of a larger crater. We walk a 2 mile out and back trail to see the tree molds, where lava incinerated tree trunks, retaining the imprint of the bark as it cooled.
By day’s end we only have a short time to see the caves formed by lava tubes – tunnels that developed when the outer lava of a flow hardened while molten lava continued to flow underneath, until the lava flow ceased leaving a hollow tube behind. Some of these tubes have collapsed exposing new caves. Visitors are not allowed to enter the caves if they carry any equipment, or are wearing any clothes that have been in caves contaminated with white nose syndrome. O and I do not enter the caves. We are pretty sure we are not carrying white nose fungus, but my camera has been in Mammoth Cave.
We return to Arco to find dinner at the town’s second small restaurant and then return to our room as a cold rain begins to fall. We were very lucky on the weather today! Our brains are foggy from all the information we have tried to absorb. If the weather cooperates tomorrow we will venture out on a longer hike through the volcanic landscape.