Zoom, baby, zoom*

For a few months now, I have been spending (wasting?) some time with a gadget called Gigapan, a robot that can take hundreds of shots of the same scene with a simple point-and-shoot camera. The pictures are taken in a well-defined rectangular grid pattern so that there is the right amount of overlap between all neighbors. Later the photos can be stitched into a gigantic photograph on a computer and shared with the world through the Gigapan.org website and, even better, through Google Earth. [If you are a tiny bit familiar with geoblogs, you must have seen some of the gigapans that Ron Schott has put together; he is one of the earliest and most enthusiastic adopters of the technology and has assembled an impressive set of panoramas on the gigapan site.]

I have to confess that I had to actually buy this thing and start playing with it to realize how different gigapixel panoramas are from the usual few-megapixel digital photographs. The idea is simple: a ten megapixel camera takes photos that contain ten million pixels; if you put together a 10×10 grid of such photographs into one image, you end up with a gigapixel panorama. Because some overlap is needed between the photographs, more than 100 pictures are necessary to exceed the gigapixel limit. But the point is that the more pixels there are in a photograph, the more information it contains and the more sense it makes to zoom in and see the details – details that are usually non-existent in a conventional digital picture. The other side of the coin is that it is only worth taking gigapans of scenes with plenty of small-scale and variable detail (although I am getting to the point that I see a potential gigapan everywhere).

I do not think that gigapixel images will replace conventional (that is, megapixel) photography. There is only a limited number of things that the human eye can see at one time; and often the value of a good photograph comes not from the pixels it captures, but from the ones it consciously ignores. Beauty and the message an image can hold are scale-dependent; and zooming in to see the irrelevant detail could be a distraction.

That being said, I am all for taking home as many pixels as possible from outcrops and landscapes in general. The gigapan system is simple and works surprisingly well, and it *is* exciting to explore big outcrop panels from the scale of entire depositional systems to the laminae of single ripples or even grains.

No photos or panoramas posted/embedded this time; but here is a link to my giga-experiments.

* title is courtesy of Kilgore661

Images from South Africa: Patterns

A few more photos from the same trip that I already posted photographic highlights from. To be more factual and fair, the title should be “Images from the Western Cape”, because I have only seen a few places in South Africa, and all of those places are in the Western Cape province. Anyway, here are three photos of… well, not much, just some visually interesting patterns.

Halophytic (salt-loving) vegetation in the supratidal zone of the Langebaan Lagoon, West Coast National Park

Old tree trunk at Groot Constantia winery, Cape Town, the first winery in South Africa, created in 1685

A look at the pebble (beach near Cape of Good Hope)

Liesegang bands in sandstone

Liesegang bands are poorly understood chemical structures often seen in rocks, especially sandstones. They were discovered more than a hundred years ago by the German chemist Raphael E. Liesegang, when he accidentally dropped a drop of silver nitrate solution on a layer of gel containing potassium dichromate, and concentric rings of silver dichromate started to form.

In sedimentary rocks, Liesegang bands appear well after the sediment has become a rock (that is, it got compacted and cemented). Stratification and lamination within the sansdtone are typically cross-cut by the Liesegang bands; fractures usually have a more obvious effect on the distribution and orientation of these.

The rocks shown here are turbidites of the Permian Skoorstenberg Formation, in the Karoo desert of South Africa. This Liesegang banding developed in the neighborhood of a small thrust and consists of brown bands of iron oxide that entirely ‘ignore’ the original lamination of the sandstone (not visible in the photos), but clearly like to precipitate along some of the fractures in the rock.

Water escape structures in a Cretaceous delta, Wyoming

I spent a few days in Wyoming, at a conference and field trip focusing on clinoforms, organized by SEPM (Society for Sedimentary Geology). Clinoforms are sedimentary layers with a depositional dip of a few degrees that form packages of relatively large thickness (let’s say more than a few meters; could be hundreds of meters in some cases. The point is that the foresets of ripples, sand dunes and other bedforms could be called clinoforms but they should not be). [Warning! – my definition]. After a couple of days of morning talks (many very good ones) and afternoon posters, we spent two additional days visiting some outcrops in southern Wyoming.

These photos come from exposures of the Maastrichtian Fox Hills Sandstone of the Eastern Washakie Basin, a sandstone of deltaic and fluvial origin that links through shaly clinoforms to turbidite sands and shales of the Lewis Shale, deposited in water depths of more than 400 meters (see reference below).

The photo above shows one set of smaller-scale clinoforms truncated by a cross-bedded sandstone unit above, probably of fluvial origin. This is a prograding shoreline. It was a matter of debate whether the erosional surface at the base the fluvial sands is a sequence boundary or not, and could be a blogworthy subject in itself, but I will refrain from discussing it here and now. What I think – at least visually – are more exciting are the water escape structures in the photograph below.

There are two sandy layers visible in the picture; the lower one is somewhat darker colored and more massive-looking than the upper one, which is more laminated and has an overall lighter color. The height of the rock surface covered in the photo is about 1.5 m.

A likely explanation for the structures is as follows (sorry for the arm-waving — it would be nice to put some numbers here – sedimentation rates etc., but life is too short for that right now). Soon after the first (darker) layer was deposited, another flood of the river brought more sediment to this location, and started depositing sand, mostly along a flat bed that resulted in parallel lamination. The underlying sediment was still very porous and unconsolidated, and some of its pore water was trying to get to the surface as the weight of the overlying deposit increased. Thin layers of finer-grained and therefore less permeable sediment got in the way however; and the escaping pore water had to travel laterally until it found the most vulnerable spots to go again upward. There are two of these vertical water escape conduits in the photo. As all the water coming from the lower layer had to go through a limited number of these spots, the velocity of the pore fluid must have increased significantly, until it actually was able to fully suspend the sand it encountered. In other words, some of the sand along these vertical escape zones got fluidized and carried away. The white structureless patches of sand are sedimentary intrusions. The light color suggest that these sands are much ‘cleaner’ than the rest of the rocks; the finer grains (responsible for the darker color) were washed away.

One interesting detail is that the trough cross-bedded sand between the two intrusions thickens into the depression, suggesting that the water was trying to get out in real time, that is, at the same time as the upper layer was being deposited.

Below I linked in an amateurish-looking gigapan; and here is another post on water-escape structures.

Launch full screen viewer

Reference:
Carvajal, C.R. & Steel, R.J. (2006), Thick turbidite successions from supply-dominated shelves during sea-level highstand. Geology, 34, p. 665-668.

Fossilized snake with exploded head

There is a temporary exhibit called “Geopalooza! A Hard Rock Anthology” at the Houston Museum of Natural Science. If you are in Houston this summer (until August 24), this is something absolutely worth checking out: you can see some outstanding geodes, crystals, meteorites, and fossil specimens. I have been to many natural history museums, but I rarely get as high as I did at the HMNS the other day [‘getting high’ is the right terminology here: you get to (or have to) listen to Led Zeppelin and Bob Dylan while looking at the rocks]. Even if you are not too much into rocks, minerals, fossils, and natural science in general, these pieces are so beautiful that they can simply be viewed as works of art.

Here is for example a fossil snake from the Eocene Green River Formation in Wyoming. This formation has not only one of the most significant fossil sites in the US, but it also contains the largest oil shale deposit in the country: there are 1.5 trillion barrels of shale oil within the former lake sediments. Preservation of both fossils and of organic matter requires special conditions on the lake bottom: a partial or total lack of oxygen not only prevents oxidation of organic material, but also makes life difficult for critters that otherwise would totally churn the sediment and leave no undisturbed animal remains behind.


One of the museum curators was around when I was checking out this snake and she explained that the reason why the head bones are in such a disarray – compared to the beautifully arranged backbone and ribs – is that, as the snake’s body started to decompose, the easiest way out for the accumulating gases was through the head.

I think this snake must belong to the species Boavus idelmani, and is probably one of the best preserved fossil snakes in North America.


The rest of the photos from Geopalooza are here.

Three photos from Vargyas Valley, Transylvania

A few weeks ago I have spent some time back home in Transylvania (it is actually a place previously known as home), and took a day to visit a special place, the ‘canyon’ of the Vargyas River; we used to do a lot of caving and hiking here when I was in high school. A small patch of Mesozoic limestones was somehow forgotten in the middle of a lot of softer pyroclastic deposits, and a nice little canyon developed, with lots of caves and typical karst morphology. Make no mistake, this is not a ‘grand’ canyon, it is not even among the largest canyons in Romania or Transylvania.

But often it is lesser known and more hidden places that have a special atmosphere, a special combination of colors, shapes, shades and minor details that you can never forget.

The Vargyas River

One of the caves

Chlorophyll rules at this time of the year

More pictures here. And here is a map:

A new way to enjoy photographs

Anybody who takes more than ten photos per year (and everybody has at least a point-and-shoot camera these days) needs a good online photo sharing service. I have been a diehard fan of Smugmug for several years now. I love the elegant, somewhat Apple-like interface, the slick animations, the ability to easily organize and tag photos, the fact that pictures can be displayed at seven different sizes, that it is easy and fast to order high-quality prints, not to mention the significant integration with Google Maps and Google Earth. While I have realized that Flickr seems better equipped for more ‘Web 2.0’ interactivity (maybe largely due to the sheer number of users and photographs), and that there are far more photographs of turbidites on Flickr than Smugmug , I find the Flickr user interface confusing and its design inferior to that of Smugmug, with a lack of style that does not do justice to the zillions of great photos that are out there on the servers.

Having said that, I have recently started to use and appreciate Flickr a lot more. The reason: the updated Apple TV can stream photos directly from Flickr. Television sets with high-definition screens might be a bit ahead of the time due to the limited number of easily (and cheaply) available HD TV programming and movies, but they are perfect for displaying even relatively low-resolution photographs in brilliant colors and surprising clarity. After all, the best HDTVs have a pixel count of 1080 x 1920, and you get more than two megapixels with most digital cameras. Sitting down with a glass of wine and discovering good photographs on a big screen while listening to music is my favorite new pastime and I think it is a lot more enjoyable than browsing photos on much smaller computer screens that usually have a lot of clutter in addition to the photograph.

Now, if Apple was smart and kind enough to put Smugmug on Apple TV as well…

Dish structures

Dish structures are sedimentary structures found in thick sand (or sandstone) that have concave-up, bowl-like shapes. They form when water is trying to escape from rapidly deposited sand but encounters horizontal barriers of somewhat lower permeability (usually zones with smaller grain size and/or dispersed mud). These force the water to flow laterally until it finds a place where it can go upward again. In the meantime, the subtle permeability differences get enhanced as muddy particles are washed away from the cleaner parts of the sand and concentrated in zones of lower permeability. The sides of these lower perm zones bend upward as the water finds its way up. Eventually pillar structures, vertical zones of cleaner sands can form on the sides of the dishes.

Initially dish structures were thought to be related to the (still somewhat fuzzy) mechanics of sediment transport and deposition in high-concentration gravity flows. However, clear examples that showed primary sedimentary structures (like cross lamination) being cross cut by dish structures proved that the latter are secondary structures, formed soon after deposition.

Probably because rapid deposition of sand is a requirement for the formation of dishes, these sedimentary structures are largely restricted to deep-water sands. Here are some examples that I think are blogworthy:

This one is from the northern California coast. Note the pillar structures between the dishes. [Apologies for the lack of scale – I think this bed is about 4 feet thick].

This is a zoom-in of dish structures in the Cerro Toro Formation of Southern Chile. Lighter-colored areas probably contain less mud than the darker zones.

No scale on this one either (there was no way I could climb up there), but trust me, these are probably among the largest dish structures in the known universe. They were photographed in northern Peru, near the town of Talara.

And to prove that they are really big, here is a photo that gives an idea of their scale: