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

Wednesday, February 20, 2019

Wave Rock, Australia: An unusual geologic feature

Wave Rock, southwestern Australia: 14-15 meters high, 110 meters long. This feature is on the north side of "Hyden Rock", a hill made of granite.  The hill is an "inselberg" (also called a monadnock), an isolated small mountain rising from a virtually level plain. The word "inselberg" comes from German and means "island mountain." They are common in Africa.
     The indigenous people of south western Australia are the Ballardong people. In their Dreamtime, the rock was created by the Rainbow Serpent after she drank all of the water in the land. She became bloated and dragged her swollen body over the land, leaving Wave Rock in her wake. The dreaming trail of this story extends from the south coast near Augusta to the northeast to the Great Victoria Desert.
     Wave Rock is part of Hyden Rock, a 2.63 billion year-old monzogranite (reference from Wiki). The inselberg consists of three domes, two of which are separated by a valley now filled with a reservoir. Between 100-130 million years ago, granite bedrock was fractured and altered by weathering to varying depths by a process known as lateritisation (a process that occurs in hot wet climates and produces a weathered product rich in iron and aluminum). This process formed
underground pods or domes of solid unweathered granite separated by deeply weathered fragments of granite. Erosion then exposed these domes to become what is now Hayden Rock. Geomorphologists call features like Wave Rock a "flared slope,"a bedrock surface that is concave-upward. Chemical weathering around the base of an inselberg preferentially develops at the base, producing a weathered and disaggregated zone.  When the land surface around the buried inselberg is then exposed as the land surface is lowered, this disaggregated zone is easily eroded, leaving the flared slope of Wave Rock.
     A wall on top was built in the 1920's to guide rainwater (in this very arid area) toward the Hyden Humps Dam (image on the lower right).

Monday, February 4, 2019

Great shock wave sequence in Space X Raptor Enginer Test Fire

In the first few seconds of this Space X engine test fire, there is a brief, but great, sequence of shock waves in the exhaust plume. https://www.cnn.com/videos/business/2019/02/04/spacex-raptor-engine-test-fire.cnn-business/video/playlists/business-news/. The sequence repeats about 2/3 of the way through. This is a well known phenomenon with structures as explained in the graphic.