Friday Field Foto #123: Sometimes you need to cross a river
This week’s Friday Field Foto doesn’t show any geology — but shows what a geologist must sometimes do to get to the rocks. In this case, I think we are on our way back from spending several days staying at the base of and climbing the mountain in the background on the right. Good times.
Crossing the Rio Zamora, southern Chile (© 2010 clasticdetritus.com)
Happy Friday!
Mud flow caught on video
This video has already made the rounds the last couple days (e.g., Geofroth and Geotripper) but I couldn’t resist posting it here. The large truck offers both scale and an illustration of the power of moving mud.
As far as I know the video was first posted here.
Writing in the geoblogosphere (week of August 23-29, 2010)
This week-in-review idea continues to evolve so bear with me. To help focus what I put in this weekly digest I’m going to highlight posts that include some interesting writing. I’m also going to limit myself to five:
- Check out this epic post from one of Callan Bentley’s students on Mountain Beltway to learn about the geology of Glacier National Park in Montana.
- Chris Rowan from Highly Allochthonous discusses a new paper documenting the fascinating interaction of a subducting slab with a continental hot-spot mantle plume.
- Michael Welland from Through the Sandglass writes about the ephemerality of islands made of shifting sand and the challenges of making maps of such transient features.
- Jessica Ball from Magma Cum Laude posts about her trip to the island of Montserrat and Soufriere Hills volcano, providing some nice background on the geology.
- Speaking of volcanoes, Garry Hayes from Geotripper discusses kipukas (islands of land surrounded by young lava flows) in Hawai’i and how they can become unique collections of various plants and animals.
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List of most recent week-in-review posts: https://clasticdetritus.com/category/week-in-review/
Sea-Floor Sunday #72: Indus submarine canyon
The ongoing flooding of the Indus River in Pakistan inspired me to search for an image of the Indus submarine canyon for this week’s Sea-Floor Sunday image. The image below is from this website describing a research cruise in 2008-2009 that acquired multibeam bathymetry data and cores. Check out the site for more details about the study.
The purple colors are deeper water and nicely show the sinuous canyon. The canyon is between 1 and 2 km wide and up to 1,100 m (~3,600 ft) deep. The tight meander bends remind me of this place. This submarine canyon feeds the enormous Indus submarine fan, which is 1500 km (900 mi) long and 960 km (575 mi) wide, second only to the Bengal submarine fan in size.
Bathymetry of Indus submarine canyon (credit: http://www.abdn.ac.uk/~wpg008/PelagiaIndusCruise.html)
Here’s a zoomed-out map from Google Earth for context.
This week’s Friday Field Foto is from some Miocene beach-cliff exposures on the Atlantic coast of Tierra del Fuego. These sandstones are characterized by a mix of ‘normal’ turbidites thick successions of traction-dominated (including large climbing dunes) deposits. Also note the surface cutting down from left to right in upper part of cliff — a nice erosional surface, which is overlain by mostly thin-bedded, fine-grained strata.
Miocene sedimentary rocks, Tierra del Fuego coast (© 2010 clasticdetritus.com)
Happy Friday!
Sea-Floor Sunday #71: Live feed from active submarine volcano
This week’s Sea-Floor Sunday image is from a site I saw linked to by various folks the past week. As part of NSF’s Ocean Observatories Initiative they have included a live feed from Axial Volcano, an active volcano along the Juan de Fuca ridge offshore of Oregon. This is a great idea and, similar to video feeds for volcanoes on land, observatories like this will be important for capturing submarine volcanic activity. Check out the daily log of this research cruise.
Clicking on the image below will take you to the page with the live feed.
Static image of this live feed: http://interactiveoceans.washington.edu/story/Live+Video
Here’s a map of the location of Axial Volcano and check out this page to learn more.
General plate tectonic map of the NE Pacific Ocean showing the North American, Pacific, Explorer, Juan de Fuca, and Gorda plates. The Coaxial Segment is just N of Axial Volcano along the Juan de Fuca Ridge. (credit: http://www.volcano.si.edu/world/vol_extra.cfm?name=Blanco%20Transform%20Fault%20Zone)
Geoblogosphere week in review (August 9-15, 2010)
Here are several posts from the geoscience blogosphere last week highlighting interesting writing:
- Michael Welland of Through the Sandglass discusses all the sand-related activities one can enjoy while visiting the Exploratorium in San Francisco.
- David Bressan of History of Geology digs into Lyell’s and others work from the 1800s with a post about the concept of cycles in geology.
- Garry Hayes from Geotripper posts an update on the whole removal-of-serpentinite-as-California’s-state-rock affair. Also make sure to see Silver Fox’s (from Looking for Detachment) constantly updated list of blog/media coverage of the issue.
- Rachael from 4.5 Billion Years of Wonder has a post titled The Great Geological Fart … need I say more to make you want to read it?
- Chris Rowan from Highly Allochthonous discusses the scale of an eruption at Yellowstone 600,000 years ago and the vast area across which the volcanic ash was spread. Chris gets double-billing for his nice summary of the recent findings that the Haiti earthquake was not associated with the Enriquillo Fault.
- Jim Lehane of The Geology P.A.G.E. is working on a comprehensive series of reviews and discussion of the scientific concepts (uses and abuses) in the disaster movie Armageddon. Check it out.
- A Life Long Scholar from The Musings of a Life-Long Scholar writes a clear and succinct post about the differences between contact and regional metamorphism.
- Zoltan Sylvester of Hindered Settling writes about the complex patterns and processes of sinuous channels by highlighting two recent papers about modeling efforts of both terrestrial and submarine channels. (By coincidence, my Sea-Floor Sunday post from yesterday also mentioned the comparison of rivers to submarine channels.)
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List of most recent week-in-review posts: https://clasticdetritus.com/category/week-in-review/
Sea-Floor Sunday #70: Black Sea submarine channel system
This week’s Sea-Floor Sunday image* is from the Black Sea side of the Bosphorous Strait and, as always, shows sea floor bathymetry (hot colors are shallower water and cooler colors are deeper water). Note the prominent channel carving its way into deeper water and then possibly splitting into smaller channels. Or maybe those are overspill channels? Pretty awesome I say.
credit: The Daily Mail
I blogged about this channel system in June 2009 and showed a similar, although much less colorful, image in this post.
The image above and the following quote are from this article in The Daily Mail.
The undersea river – the only active one to have been found so far – stems from salty water spilling through the Bosphorus Strait from the Mediterranean into the Black Sea, where the water has a lower salt content. This causes the dense water from the Mediterranean to flow like a river along the sea bed, carving a channel and deep bank.
The second sentence of that statement is a good one — it explains the mechanism for the origin of this submarine channel system (i.e., saline density currents that hug the sea bottom) and mentions it forms a geomorphic feature similar to a terrestrial river. But the first sentence causes my inner nerd to itch a bit. Firstly, submarine channels are not “undersea rivers” — at least, I’ve never heard anyone else who studies these features call them that. The quote from the researcher included in the piece is simply painting a picture for a general reader that the geomorphology is similar to a river. Secondly, what exactly is meant by “the only active one to have been found so far”? If they mean the active submarine channel systems then, no, this is not the only active one — there are numerous submarine canyon-channel systems that have transmitted density currents in recent decades (e.g. Monterey, Var, Hueneme, Congo, etc.). Perhaps they mean the only active system in which a saline current is the dominant agent? I’m not sure about that — maybe some of my readers could comment on that.
Don’t get me wrong, a discussion about what aspects of submarine channels are similar to rivers and what aspects are different from rivers is a discussion very much worth having. In fact, having that discussion helps us understand these features much better. But, I’m not ready to let the mainstream press and the general public simply call these ‘undersea rivers’ and be done with it — there’s still far too much to learn.
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* pointed out by @jeffersonite last week
Friday Field Foto #121: Muddy tidal flat in the Arctic
This week’s Friday Field Foto is from the Adventdalen River mouth near the town of Longyearbyen, Svalbard.
Muddy tidal flat, Adventdalen River mouth, Svalbard (© 2010 clasticdetritus.com)
Check out more photographs from a trip I took to Svalbard in June 2009 on this Flickr page.
Clastic Detritus 
