Thursday, May 7, 2015

Kīlauea Topography

Later today I'll be taking a trip to Hawai‘i Volcanoes National Park to see the lava lake in Kīlauea caldera. In case you haven't heard: Kīlauea has had a lava lake in its summit caldera constantly since it began its current eruption on January 3, 1983, however, the level of the lake has fluctuated over time, and for most of its existence has been very low – too low for tourists to see from safety, and only visible with cameras set up on the very rim of the crater. Just recently, within the last two weeks, the level of the lake has risen dramatically, making it easily visible.

But wait – I'm using terms like caldera and crater willy-nilly here without definition. Kīlauea the volcano has a slightly complicated summit, and there are several names bandied about when talking about it. This post is as much for my sake as it is for yours, but I'm going to try to map out exactly where all the various names refer to. First of all, have a Google Maps view of the area:

This is a satellite photo of the area around the summit caldera of Kīlauea. This picture is mostly for reference. For actually pointing out the various parts, I've created the following picture with various regions colored in for clarity:

Here's the summit region again, with significant features colored it. Shown in red is Kīlauea Caldera. Calderas are a common feature at the summit of volcanoes, and are formed when the summit of a volcano collapses after a particularly strong eruption – the magma in the magma chamber has been erupted and can no longer provide support to the overlying rock. It's likely that Kīlauea Caldera was formed over several centuries, and may have attained its current form after a particularly violent eruption in 1790. I'm not 100% sure of these boundaries, as the walls of the caldera steadily diminish to the southwest where lave has spilled out, and there may be a small lobe to the northeast that I haven't included, but the outline is close enough.

The smaller green area within the caldera is Halema‘uma‘u Crater. (Remember my tips for pronouncing long Hawaiian words with reduplication! It's Hale·ma‘u·ma‘u.) Halema‘uma‘u Crater is a smaller pit crater within the larger caldera, and has been the location of most of the volcanic activity at the summit for quite a while (though not all of it; directly to the east of the caldera in the picture above you can see the pit of Kīlauea Iki where an eruption happened in 1959 that created some of the tallest lava fountains ever recorded).

Finally, within Halema‘uma‘u crater, colored in blue, is Overlook Crater, named for…I'm not really sure, actually. I guess the fact that it can be seen from the overlook at the nearby Thomas A. Jagger Museum. This is the actual volcanic vent, and has in the past taken the form of a yet smaller crater within Halema‘uma‘u crater. This is where the lava lake I talked about has actually been residing, usually far enough below the surface as to be unseen from the overlook.

However, starting on April 24th, the lava lake inside the vent rose almost to its lip (at the floor of Halema‘uma‘u crater), the highest it had ever come since the vent opened. As of April 29th the lava has actually risen enough to spill onto the crater floor, and has since fluctuated around the level of the floor of the crater floor. It's clearly visible from the overlook, and a lot of people are going out to take a look, including myself. If all goes well I hope to have some pictures of it soon, and with this post under your belt you'll be able to follow what I'm talking about when I casually throw out names like “Halema‘uma‘u crater.” A hui hou!

Edit: Well, maybe this'll teach me to announce things ahead of time. Turns out, due to unforeseen circumstances, several of the people I was planning on going with couldn't make it today, so we're postponing to a later date yet to be determined. I'll be sure to write about it when it does happen, though.

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