This is just awesome:
The flow looks like it’s really cooking along… until people make an appearance in the video and you see just how much it’s been sped up. The flow is actually moving at around 50 cm per hour, which to us fast-living humans makes it practically solid ground.
More info over at the AGU Landslide Blog.
And I totally agree with the first commenter over at the post. This thing needs some Benny Hill music, starting right when the first person pops into the frame. WIN.
Lunch today was quite fun; we had a “lunch and learn” that involved a lot of really tasty brownies and an hour-long talk by John M Holbrook. It was for the most part a general overview of the surface process quirks of meandering rivers and how those affect their usefulness as reservoirs. Most basically, oil companies like drilling in point bars since that’s where the best sand packages are to be found. Understanding the complex ways that rivers meander and stack up point bars over time (and that coarse channel fill can act as a fluid transmitter between sets of point bars at times) is a way to try to maximize drilling effectiveness.
Not that mapping out historical meanders is an easy task even for a river that’s still active and not buried hundreds of feet down and only visible via cores or seismic. Dr. Holbrook used a particular section of the Mississippi River (where it crosses the New Madrid seismic zone) to illustrate these concepts, and said that when they were trying to map out the old meanders by taking sediment cores, they were wrong about 30% of the time.
I thought the most interesting part of his talk was a brief look at fluvial response to tectonic activity, particularly how a river reacts to displacement on a fault that it crosses, since that normally means a change in grade on both sides of the fault. Looking at the Mississippi’s reaction to the displacement on the faults it crossed, the basic response was for the river to straighten out (cutting off meanders) on the downdropped side of the fault (where the gradient decreases) and resume meandering on the uplifted side. Which makes a lot of sense, really, though the other interesting thing was how quickly this response occurs. (Answer: very quickly.)
He’s got a paper in the pipe1 about using the Mississippi to examine tectonic activity on the New Madrid fault, which is currently in review for Tectonophysics. Apparently it’s a bit controversial since what the river seems to show is that earthquakes along the fault system are temporally clustered, which doesn’t necessarily fit with the current consensus on the seismic zone. So I hope that it does get published and I can find a way to get my hands on the paper, since it sounds like an interesting read.
1 – If it gets published, here’s the title: Restored river courses reveal millennial-scale temporal clustering on a midplate fault
There’s a lovely blog post over at The Planetary Society explaining a couple of images from IAG’s Planetary Geomorphology Working Group’s May 2010 featured images.
This is some cool stuff, since it’s very much connected to the ongoing “water on Mars” debate, and the geomorphological argument has to do with water leaching minerals over a fairly long period of time. Another of the images that the blog post doesn’t cover looks at:
However, with the addition of infrared color, two distinct units of altered minerals can be discerned, and using spectroscopic information, these have been identified. Here at NE Syrtis, there is a unique stratigraphy of iron sulfate overlying carbonate, which is being exposed by the erosion of overlying lavas (Mustard and Ehlmann, 2010). This suggests a transition in the aqueous alteration environment from neutral-to-alkaline to acidic that is preserved in the rock record.
Aqueous alteration environment… squee! With of course the added fun of wondering what might have caused the pH of that environment to go from neutral-ish to acidic. Interesting stuff, to be sure.
I didn’t know about the images of the month, but I’m going to start checking them out for sure! Geomorphology was one of my favorite undergrad classes, and there’s some very neat stuff on that site. For example, comparison of catastrophic flood bed forms on Earth and Mars that was April’s set of images. Looking at land features via aerial/satellite imagery isn’t perfect, but I think it’s great to see our knowledge of our own planet being applied to the images we’re getting from Mars.
Alfalfa Sprouts Key To Discovering How Meandering Rivers Form
Some very cool stuff from the world of Geomorphology. Now that we’re realizing that channelizing rivers sometimes isn’t the best idea (well, as far as the flood plains and nearby shores are concerned, it’s never a good idea) and trying to get them back to their natural state, we’ve never managed to copy nature. We can put a man on the moon, but we can’t make a meandering river, to paraphrase. So this is some very cool modeling on how the process works, which means some day we might be able to get the meanders right.
*Quick terminology: Meandering rivers are those wandering, looping rivers we’re so familiar with. Such as The Amazon or the Mississippi or the Nile. You’re probably not familiar with braided rivers unless you live near the mountains or other sources of extremely coarse sediment, but here are a couple examples: Waimakariri River, drainage near the Yukon River. Basically, braided rivers have a lot of in-channel sediment deposits that the river cuts through in a multitude of small channels.
I definitely want to see if I can get my hot little hands on a copy of their results. It sounds extremely interesting. (Though I’m sure all the really technical stuff will make my head spin.) Also, the researcher does bring up some good questions about Mars and Titan. We can be pretty sure that neither place has or ever had the verdant banks that would help build meanders. So the real question is, how would meanders form in an environment without vegetation? What would provide the bank stability that lets the point bars grow? Maybe that’ll be the next experiment, after they’re done with their alfalfa jungle.
By the way? Best use for Alfalfa sprouts outside of a turkey sandwich. Truly.
