An amazing area to check out. The drainage ignores...but not entirely...some elaborate folds in the desert.
Orbicular pathology in the Libyan Desert
Back to the deep desert for me. Here's an unearthly scene in Libya.
http://www.flashearth.com/?lat=24.987853&lon=16.513563&z=13.3&r=0&src=msa
The latest Where on Google Earth image featured a gorgeous alluvial fan in the Zagros mountains of Iran. The Google Earth imagery does not show this fan in flood, but an ASTER image from a few years ago does.
Image credit to: NASA/GSFC/METI/ERSDAC/JAROS and U.S./Japan ASTER Science Team
Link to NASA ASTER image gallery: http://asterweb.jpl.nasa.gov/gallery-detail.asp?name=iranfan
I'd say see for yourself in Flash Earth, but unfortunately the imagery appears to be pretty poor quality for this area: http://www.flashearth.com/?lat=28.994958&lon=55.049338&z=8.5&r=0&src=nasa.
A different kind of flooded fan, lower Verde River, AZ
Inundated fan really. Along the lower Verde River in Arizona lie two dams. The upper dam creates Horseshoe Reservoir which is seasonally filled and drained to feed Phoenix's water needs. While out mapping in the area we took the opportunity to explore the are below the high water line while the reservoir was empty. Numerous small fans spill into the reservoir and onto what was the former river's floodplain. On one of these fans lies an interesting structure, a Hohokam era ruin. The seasonal filling of the reservoir results in a high water line of driftwood, and trash near the apex of many fans. The fan channels seem to fluctuate laterally more dramatically during low reservoir levels probably due to the constant backfilling of tributary channels, addition of lovely layers of pond much, and the ubiquitous cocklebur plants covering the reservoir bottom. Horseshoe Reservoir is an interesting place but I'd wager it was much nicer before the (damn) dam.
Reservoir empty, ruin just to the left of the crosshairs
Low walls of the ruins can be seen in the middle ground. Now covered by reservoir mud and cockleburs. The riparian trees in the background line the modern low reservoir level Verde River
Ruin wall. Otter feces were found on another portion of the ruin so at least it still gets some use
Supremely flooded fan in Pathologistan. Really nice one.
Also with some color and contrast enhancements. This one really shows some nicely elaborate yet systematic flow patterns.
http://goo.gl/maps/Bgmy
Clearly this general area was hit with a large precipitation not too dreadfully long before these images were taken. Yes, I monkeyed with the color balance and exposure to light-up the fresh channel. Overall, this area looks pretty 'tan'.
Go to the previously posted site in China and head upstream. Amazing on many fluvial and alluvial levels...(pun).
Large alluvial fan flood features and a real fan flood in China
Once again, the system of tubes, the so-called 'internets', for the win. Another friendly reader located a stellar example of alluvial fan flood evidence, this time in China. This is an immense fan with a multitude of abandoned channel tracts including obvious signs of major avulsion events near the fan apex. Bonus.
But wait, there's more! As an added bonus, upon zooming in, I learned that the high-res imagery in Google Maps actually captured an alluvial fan flood in action on the fan of interest and on an adjacent fan. Nice.
Go check this area out. Very interesting geology abounds, as always, in western China.
Flooded fans in Pathologistan
Friendly reader Billiard Traveler just led me to some spectacular alluvial fan flood evidence in what appears to be a particularly hyper-arid part of Pakistan. The entire region in which these fall fits many variations of geomorphologically pathological (just look around a little), but only a couple of the fans are showcased here.
Another nice example of the effects of a large flood on an alluvial fan. Link below, but GE image better.
Alluvial fan floods...maybe not so pathological...but pathologically hard to manage and mitigate. I am currently working on a career-long project that deals with these little monsters and I would appreciate some help finding stellar examples of such events anywhere in the world. For example, this one I have posted of a significantly channel modifying flood in Baja California. Look in particular for evidence of channel avulsion on fans or, better, fan floods that appear to have not paid much attention to the pre-flood distributary channel array. My goal is to find representatives of a potential continuum of geomorphic responses to large floods or debris flows on alluvial fans in a range of physiographic settings.
Particularly illustrative global examples of alluvial fans also accepted. Please help!
Pathological Confluence in Russia
This complicated conflation of channels and channel patterns near the confluence of the Urmi and Amur Rivers in the Jewish Autonomous Region of Russia is mesmerizing. Seriously, go check it out. http://www.flashearth.com/?lat=48.611358&lon=134.983387&z=11.4&r=0&src=msa
I'm late for October's theme of interesting juxtapositions of geomorphology and human landscapes, suggested by Brian Romans. So before someone selects November's theme, here is my contribution.
We have had mainly fluvial/alluvial and tectonic geomorphological features, but so far not any volcanic ones. The image here is a maar, a volcanic feature generated by phreatomagmatic eruptions due to the interaction of groundwater with magma. This example is the Álvarez Maar from the Michoacán-Guanajuato volcanic field in Mexico. The feature sits on a dry plain in the Valle de Santiago area but water tends to collect in the crater making more fertile soil for agriculture. You can explore the Michoacán-Guanajuato volcanic field on flashearth here.
The moment I learned from this month's theme I quickly thought of Junin. Junin and Carhuamayo are 2 towns built on alluvial fans right downstream from the Eastern Cordillera and at the edge of Lake Junin, in the Altiplano of Central Peru (note that the image is rotated). As you can imagine, these fans are composed of sediments from glacial valleys, many of which are still occupied by glacial lakes upstream, the only evidence of now almost gone glaciers in the area.
Quick fact (if you didn't click on the Wikipedia link): Lake Junin is the biggest lake inside Peru since, as you may know, Lake Titicaca is shared by Peru and Bolivia.
This is my first post here at Pathological Geomorphology and I bring you some imagery from my home state of Louisiana.
Before the mighty Mississippi River was confined to its current course via the construction of artificial levees and control structures, the large river often overflowed its natural levees leaving behind overbank deposits of mostly silt, clay and mud. Today, the legacy of natural levee building processes is manifested in the form of land developed and settled by the early wave of European settlers. The French "long-lot" system was systematically employed, which granted river access to the greatest number of people, and is clearly still visible today. No new groundbreaking observations here, but certainly spectacular in map view.
The image above is taken from a reach adjacent to the Mississippi between Baton Rouge and New Orleans.
Flash Earth permalink: http://www.flashearth.com/?lat=30.033628&lon=-90.683757&z=12.4&r=0&src=msa
Heppner, Oregon and its roller-compacted concrete backstop
The cross-hair in the Flash Earth image below is just behind home plate at the city's baseball field. Note the backstop...the Willow Creek Dam. Sure, it is pretty much the backdrop for the whole town, but the proximity to the ball field is just...so...close.
Further reading...worth a look, for sure:
Hmmm...interesting. Think you should go check it out: Flash Earth link
Continuing on the theme of the intersection of geomorphology and human-made surface patterns, this is from central Pennsylvania and nicely shows how the farmland (the lighter colored patchwork) follows the plunging ridges (dark green) of anticlines and synclines.
Pathological palimpsests: desert alluvial fan irrigation
I love the idea set forth by Brian R. this month. Anne J.'s example of fan and irrigated valley interface sparked my memory of some interesting constrasting examples wherein the full geometry of alluvial fans is laid bare by irrigation on them.
Alluvial fans are often milked for all they are worth in many of the world's deserts. Particularly well-watered fans display a remarkable palimpsest of culture and fluvial geomorphology.
This first example is from Afghanistan:
This huge example is from nearby Turkmenistan:
Of course, Xinjiang Uygur has some excellent examples:
Including this particulary pathological, almost cubist, palimpsest scene:
Outlining alluvial fans by irrigated fields
Inspired by Brian's theme for the month, this basin and range landscape in central Idaho caught my eye. I love the way the center-pivot irrigation boundaries outline the edges of the alluvial fans. Closer examination reveals even more juxtaposition, as a river cuts through the middle of the valley, further limiting the extent of agricultural and human influence. I'd imagine that the arable areas have been somewhat dynamic of historical time as the river changes course and as the fans continue to build. In the second image, you can see some incomplete irrigated circles, where presumably the alluvial fan is too active to allow agricultural productivity.
The flash earth imagery is also rather nice. http://www.flashearth.com/?lat=44.553052&lon=-113.819471&z=11.9&r=319&src=msa