This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Banner image is by Ludie Cochrane..

Susan Kieffer can be contacted at s1kieffer at gmail.com

Tuesday, June 26, 2018

New video of Halema'uma'u Crater; and a great roll cloud in Tennessee

There is a 4-minute long UAS (Unoccupied Aircraft Systems) video released by the USGS today showing the enormous collapse features around the rim of Halema'uma'u crater. Filming was done two days ago on July 24. The trailer at the end of the video (which flashes by before you can read it!) says that the two flat surfaces that have subsided are the former caldera floor and the former floor of Halema'uma'u.
Photo as credited in text.
      On another topic, Colby Hutton of Adamsville, Tennessee took the adjacent photo of a roll cloud in Tennessee after a thunderstorm. A roll cloud is a subclass of "arcus clouds," low horizontal clouds (the other main type is a shelf cloud).  Roll clouds, according to Wiki, form along the leading edge of thunderstorm outflow where cold outrushing air lifts warmer air up to a level where condensation occurs, giving rise to the cloud. The most famous occurrences of roll clouds are the so-called Morning Glory clouds that form in Queensland, typically in September and October. These clouds form where air temperature reverses from its normal state (warm air at the bottom of the atmosphere, cooling upward), resulting in warm air on top of cool air. Shear across the inversion point (where the gradient changes) sets up the rolling motion, giving rise to the roll cloud.  They can last for several hours, be several hundred kilometers in length, and occur in sets. Conditions for the inversion are most likely to happen in the morning and hence the name "Morning Glory" in Queensland. They are not common--conditions for their formation are common in the spring in the midwest, but I lived there for 10 years and never saw one.  If there is too much moisture around, as in a thunderstorm, any roll cloud may be hidden amongst other clouds. Here's a link to a National Geographic short video of a roll cloud in Texas, and here's another spectacular compilation, not sure where it is from.

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