A couple weekends ago, I drove up to Craters of the Moon National Monument. It was a nice trip, though a vague out-of-sorts feeling and a late departure led to a fairly short trip.
I’m not too worried about scheduling a return trip, however, since it’s closer than the grocery store. For serious.
On the drive up, I was really impressed by the erosion of the nearby hills, and the really nice alluvial fan beneath them.
On the other side of the road was this really nice tumulus.
When I first arrived, I took a short, quarter-mile walk along the North Crater Flow Trail.
These large blocks are pieces of the North Crater that broke apart, and were rafted along in the lava flow. This may look like a really flat expanse of lava, but it’s much more textured in other areas.
This is some ropy pahoehoe lava from that same area. This forms when the lava has a very low resistance to flow and is also flowing relatively quickly, usually near the beginning of the flow. The skin that forms on top the flow gets pushed forward by the onset of more lava, much like when you stir cold hot chocolate. (My advice: pull that off. Nasty.)
Do you see the extrustion of lava flowing towards you here, across the top of a flatter section of lava? This is called a squeeze up, and occurs when the pressure inside a flow forces lava through the thick crust above it. In this case, it occurred at a pressure ridge – a section where the pressure inside a flow built up, and created a ridge.
After that, it was time for the ranger-led tour of Indian Tunnel, a lava tube. My first experience with lava tubes was here, so I was intrigued to see if it measured up to my remembrances. When I was 13, it was the coolest thing ever – I took notes the whole way, complete with sketches. (For serious.)
I’ll be honest, since I have more lava cave experience now, it wasn’t overly impressive – there are much cooler caves elsewhere on the Monument/Preserve, including some of the best lava caving I’ve done.
However, Indian Tunnel definitely is a good one for kids – the cave segments aren’t long enough for natural light to disappear, and it’s an easy walk. The children on my tour seemed totally excited, especially two boys who made Good Photo-Ops For Mommy a goal. (“Get a picture of me up here, Mom!” “Come take it from over there!”)
The cave is in a part of the Blue Dragon flow, named because it has this crazy blue sheen to it – it’s much brighter in person. It’s rather strange looking, and apparently scientists don’t know why it occurs.
This is about the longest section of darkness, and the end of the tour. You travel along the flat floor of the tube up to this point, where crossing some breakdown is necessary at a skylight.
This is a small example of a bench at the skylight. This occurs as the tube curves, and the inside edge slows down enough to cool somewhat. They can be much more dramatic than this, but this also showcases some nice lichen formation – that green stuff on the wall.
(The white sections are either secondary mineral deposits – probably calcite – or pigeon poop. Here’s something I learned on this tour: pigeons aren’t native to Idaho – they were brought in by the US Calvary, as carrier pigeons. If I ever meet a US Calvary man from that era, there are a few choice words I’d like to say to him.)
This is an example of the ceiling in Indian Tunnel. You can see the white calcite deposits on the ceiling here, which made the ceiling look like meringue to me as a child. The floor was much more brownie-like. (I might have been hungry…)
This is looking back at the skylight, after crossing the small pile of breakdown. Skylights are places where the tube’s roof has collapsed, which can occur in a variety of ways. If it occurs after the roof has cooled, but while the lava is still flowing, the breakdown can be rafted away from the entrance. If it occurs after the roof has cooled and the lava has stopped flowing, it creates this pile of breakdown, which is a joy and a pleasure to clamber over.
After you cross beneath the skylight, you enter another short period of cave, and then climb out another skylight. Viola! The cave is over.
Your reward for making it to the end is a short hike across a barren lava field, where you can admire some more flow features.
All in all, it was an enjoyable trip. Next time, I’m planning on leaving earlier, so I can hike some of the longer trails, check out some other caves, and get a better look at the spatter cones and tree molds.
Note: I'm trying Windows Live Writer out. I'm hoping it will enable me to draft posts off-line, and then quickly post them when I can get on-line. That's why the pictures are small in this post.