Lola, the cartoonist’s companion

It’s been a while since I’ve posted any photos of my supremely helpful cat Lola on the blog, so here you go:

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Lola loves to sit on paper, so when I break out the sketchbook to start working on my monthly cartoon for EARTH magazine, she sidles right up and stakes a claim. Fortunately, I was able to continue working in this case, as she wasn’t perched on the “active area” of the paper.

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As you may be able to discern, the cartoon is about the newly-fraught relationship between geologists and the law… watch for it in December’s issue of EARTH.

Two xenoliths

On my last day in Ankara Turkey (last Friday), I took the afternoon off from the Tectonic Crossroads conference in order to pay the requisite visit to the Museum of Anatolian Civilizations. I say “requisite” because Ankara’s not quite so thrilling a town as Istanbul, but this is the one location that everyone agrees is worth a visit. The previous day at breakfast in our hotel, University of Georgia geology professor Jim Wright told me it was the most amazing place he had ever seen. So I had to go check it out for myself.

It’s a cool place, if you’re into history. Anatolia (the Asian part of Turkey, which is to say, most of Turkey) is a place steeped in history. Their written records go back 9000 years, if you include Neolithic cave paintings. It’s pretty neat to check out their sculptures and tools over that long span of time. (See some photos here.)

I only took one picture in the museum, though. This is it:

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That’s a Hittite lion sculpture made of porphyritic andesite. I took his portrait because of that funny looking eyebrow — that’s a little black xenolith, a chunk of pre-existing solid rock that got stoped off the wall rock and carried along in the flow of magma, eventually getting trapped in “alien” territory once the magma (or lava) solidified around it into rock. It was the most striking geological aspect of the museum’s many displays.

After I got “museumed out” (usually this takes about 2 hours), I went for a walk around the adjacent “Citadel” region of old town Ankara, and what do you know, but I found an outcrop there! Not only that, but there were some striking similarities to the photo I had just taken in the museum — it was a porphyritic volcanic rock (I want to call it a rhyolite based on the pink color), and it too had a lone dark xenolith:

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A little girl wandered up to me with unabashed curiosity — why was this foreigner putting a lira coin on the rock and taking a photo of it in the rain? Plainly, I must be insane. I greeted her, pocketed my coin, and strolled on, reflecting on the satisfaction of seeing such a nice little pairing of similar structures in similar rocks — a quarter mile from one another, though in very different settings.

Building stones of the Haghia Sophia

The Haghia Sophia (or “Ayasophia”) is an astounding building in old town Istanbul. It is an ancient cathedral turned mosque turned museum. Through all these incarnations, the Hagia Sophia has retained some features and had other ones added on: it is a palimpsest of architecture, symbology, and history. Walking through its soaring main chamber, or side passages and alcoves, visitors like me stand with necks bent and mouths agape. It is an unparalleled location for peeling back the layers of time.

Built in 532 CE by the Emperor Justinian, the cathedral rose on the same spot where two earlier churches had stood, the first of which was built in 360 CE. The name “Haghia Sophia” comes from the Greek for “holy wisdom.” For more than a thousand years, it served as the principal church of the Byzantine Empire. It was the world’s largest cathedral for thousands of years. The minarets were tacked on in 1453, after Constantinople fell to the Ottoman Empire:

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There’s a gazillion aspects of this building to discuss, but today I’d just like to share some images of the different building stones seen in and around the Haghia Sophia. To start with, here’s a “Verde Antique” (serpentenite breccia) sarcophagus outside the building:

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The floor stones in an interior hallway, worn smooth and shiny by millennia of human shuffling:
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And a bunch of shots of stones used in the interior walls …

Granite (verging on unakite?):

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Conglomerate:

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Rhyolite porphyry:

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Rhyolite porphyry with xenoliths (also used to construct a sarcophagus outside):

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Marble gneiss:

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Darker granitoid:

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There are also some structurally interesting rocks, like this red and white marble breccia that shows pressure solution. Notice the sutured boundaries of the white grains, and their pronounced long axes, 90° to that maximum pressure direction.
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Kind of reminds you of the Purgatory Conglomerate, right? (Me too.)

My favorite rock there is this lurid, gory red/white/black marble gneiss, as it displays ptygmatic folding (elsewhere it is also boudinaged):
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I wish I had more photos of this stuff. It’s great. It reminds me of guts!

Here it is in a typical display (pardon the blurriness of the photo): they “fillet” the rock and spread it open in the manner of a Rorschach blot. This produces an attractive symmetrical design, with minimal artistic effort:
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Another nice “butterfly” spread, this one of folded marble gneiss:
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Another one:
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Look close at this one. Note the little gray crosses in there? Let’s zoom in…

Here’s one closer-up:

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These are ancient Christian crosses, or rather, the holes where ancient Christian crosses were once mounted on the wall. When the Haghia Sophia was converted to a mosque in 1453, these Christian symbols were removed, and the holes cemented over to obliterate traces of the old religion. Here’s another one, where the cement has fallen away:

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Along similar lines, here’s some Arabic script carved into the railing of the second floor, marring a lovely marble breccia:
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Stuff like this just floors me. I mean, think about all the different people to lean on this railing over the past 1500 years. The Haghia Sophia’s history is so deep, with so many distinct overlapping layers. The mind reels…

A fantastic concentration of building stones may be found at the “Coronation” spot on the main floor of the building, where Byzantine kings were crowned:

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After several pleasant hours touring the Haghia Sophia, we got lunch at a great cafe nearby. Lily got lentil soup:

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…and I got an amazing pide, the Turkish style of “pizza”:

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Delicious rocks followed by delicious repast! Can’t complain…

The Blue Mosque

In Istanbul over the summer, Lily and I checked out the “Blue Mosque,” named for the predominant color of the mosaic tiles in its interior. It’s more formally know as “Sultan Ahmed Mosque,” named for the sultan who commissioned its construction in 1609. It is an elegant building:

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I loved the “pile of bubbles” effect of the multiple domes, and then the skyward piercing forms of the minarets.

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It also cuts an impressive silhouette at night:
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The mosque is open to the public, including tourists. To visit it, you are asked to remove your shoes. Women are asked to cover their hair. Here’s Lily in the appropriate garb:

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I was shocked to see how many tourists completely ignored this request, whether out of contempt for the fact that Islam treats men and women differently, or out of sheer cluelessness. I’m no fuddy-duddy, but it seems to me that when you’re visiting a house of worship, you should follow the requests of the host faith.

Once inside, we got a look at the tiles for which the place is named:

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There were some interesting uses of building stones. Consider this arch, made of alternating blocks of conglomerate and marble gneiss:

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The ceiling of the Blue Mosque soars high above, decorated with more tiles:

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An ugly addition to this elegant architecture is a rack of lights, loftily called a “chandelier,” suspended on long cables. I thought this modern tack-on was rather tacky, but I guess it makes prayer easier in the dark hours:

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The ceiling is held up by four enormous pillars; many architectural critics find these ungainly and obtrusive:

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After our visit, we went to get some traditional Turkish tea at a little place overlooking the Bosphorus. The tea is very sweet, but comes with extra sugar cubes regardless:

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Here’s the view of the Bosphorus, the straight separating European Istanbul from Asian Istanbul. You’re looking north in this photo, with Europe on the left, and Asia on the right:

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Rocks of Glacier National Park

This is the second of my Rockies course student projects that I wanted to share here on the blog: it is a guest post by Filip Goc. Enjoy! -CB

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The Rocks around Glacier National Park, Montana: Introduction to the formations

The geology around Glacier National Park is great for beginners because the area is structurally straightforward and formations are generally easy to distinguish. Still, there is a lot to be excited about.

The rocks exposed firstly from the top down are old sedimentary rocks of the Belt Supergroup. It is called “Belt” after Belt, Montana, and “supergroup” because it is immense. These rocks were deposited in a Mesoproteozoic (1.6-1.2 Ga) sea basin, and show little to no metamorphism despite their age. Below belt rocks that make up the peaks of Glacier NP, there lay Cretaceous (~100Ma) shales; which brings us to the structure. How can these young shales get underneath MUCH older Belt rocks? Yes, there is a major thrust fault, and it is called Lewis Overthrust.

Simply put, the Belt rocks were first deposited in the sea basin. Then, Paleozoic rocks were deposited, but they are not exposed in Glacier NP, as they have eroded away. Then, Mesozoic rocks, including the Cretaceous shales and sandstones of the Western Interior Seaway, were deposited. Around 150-80Ma, as a result of the Sevier Orogeny, a HUGE slab of Belt rocks hundreds of miles wide and 15-18 miles thick slid over the Cretaceous formations more than 50 miles east! Slabs just love to glide on shales with their weak planes. Mr. Maitland from our group would call it the Banana Peel Principle, although most geologists who love French as much as I do prefer a much more refined term décollement horizon (yes, it is essentially a banana peel).

Check it out in this photo. The Belt rocks of the Altyn and Appekunny formations comprise the cliffs. They are much more resistant to erosion than the weak Cretaceous strata underneath them (low hills covered in trees). The striking white layer in the Appekunny formation is a quartzite bed.
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Then erosion took the stage with its rivers and mass wasting. Finally, around 2 Ma the Ice Age came, and we derive the name of the park from the enormous glaciers that carved the peaks into their current shapes. The last of these huge glaciers melted ~12,000 years ago, and some people think the park should therefore be named Glaciated Park, ExGlacier Park, or just Glacier-No-More. The glaciers to be seen there today are young and tiny.

Glacier National Park is a great place to educate kids about geology because many formations can be identified by their colors. From old to young, there are Altyn (and Prichard), Appekunny, Grinnell, Empire, Helena (or Siyeh), Snowslip, and Shepard formations. Let’s get color-wise. First above the Lewis Overthrust are the light gray to white (or weathered into light tan) layers of limestone and dolostone of the Altyn formation. The Prichard formation exposed on the west side of the park is essentially of the same age as Altyn, but was deposited deeper, and is therefore darker as there wasn’t as much of oxygen in the depositional waters. It consists of dark gray to black argillite with slate-like appearance. (Argillite is slightly metamorphosed mudstone.) Then there is light green or burgundy argillite of Appekunny formation. Both versions have the same iron content, but the purple version is more oxidized. It was deposited closer to shore than Altyn. The Grinnell formation is the one dominated by burgundy argillite. The Empire formation is a transitional formation between Grinnell and Helena. Helena consists of medium to dark gray dolostone and limestone, often covered with honey-colored weathering rind. The Snowslip formation features red or green argillites, shades of orange or yellow, rusty colors, purple tones, white quartzite… pretty much “rainbow rock.” The Shepard formation is similar to Helena, gray limy rocks with orange buff.

Now for the fun stuff:

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The Prichard formation is exposed on the west side of the park; is essentially of the same age as Altyn, but was deposited deeper, and is therefore darker as the increased pressure produced biotite. It consists of dark grey to black argillite with slate-like appearance. Aren’t these potholes beautiful? Also notice the joint sets. The diameter of the larger pothole is ~55cm.

There are great features to be seen in the Grinnell formation.
In this picture from McDonald Creek, there is cross-bedding in white quartzite, and a cross-section of ripple marks! A stream dumped sand onto muddy shore, ripples were created, and then mud leveled them out! Quarter for scale.
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Annotated:
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Close-up:
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In this outcrop there are some mud cracks filled in with sand, exposed in cross section view:
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There’s also cross bedding, and mud chip rip-up clasts. When the muddy shore gets exposed to the sun (low sea level), the mud dries up, loses volume, contracts, and cracks. That’s when a shot of sand came, probably with some rainstorm. Quarter for scale. As you can see in this picture of present-day drying mud, in the next stage mud cracks curl up:
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Streams or waves can easily carry those “chips” away, and deposit them with sand. That’s the mudchip rip-up clasts. Very cool outcrop!

These are just another batch of nice mud cracks in Grinnell formation. Boot for scale.
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This boulder has mud cracks overprinting ripple marks. Two in one! Swiss Army knife (11 cm long) for scale.
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This one has it all. Cross bedding, mud chip clasts, ripples, and mudballs. Field notebook for scale.
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These strange ripples in the Shepard formation are called interference ripple marks. They form when two currents go against each other at ~90°. Field notebook for scale.
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Folded argillite and quartzite of the Grinnell formation with preserved ripple marks. Car keys for scale.
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A bit more of the structure within the Grinnell Formation. This beautiful faulted fold lies on the way to Grinnell Glacier. Field notebook for scale.
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Here’s a fold that hasn’t yet been breached by a through-going fault. Width of field of view is about 30 cm.
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Note on prominent RED color in Glacier National Park: These red beds above St. Mary Lake are Grinnell formation.
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Within the Helena formation, there is a conspicuous layer of diorite with contact metamorphosed rock above and below it – the Purcell Sill.
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Part of this piece of Purcell Sill diorite has been altered to make the green mineral epidote. The horizontal field of view is ~80cm.
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So when one hikes in the area at or above Purcell Sill, all the Grinnell is way down in the stratigraphic column. The red mudstones exposed around the center of the park ( like around Logan Pass) are mostly of Shepard formation. They look a lot like Grinnell, but they are younger. The width of the rock in the foreground is ~ 1m.

Mudcracks in Shepard formation near Hidden Lake. The trail to the Hidden Lake has one of the thickest Shepard exposures in the park.
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There is one more red formation, even younger than the Shepard. This is the Kintla formation. Most visitors don’t encounter the Kintla. It can be seen as a red cap on the tops around Logan Pass (even above Shepard.) There are also exposures around Waterton Lakes on the north side of the Canadian border, and, of course, around Kintla Lakes and Hole-in-the-Wall on the northwest side.

This cross-section of mudcracks at the Boulder Pass are possibly within Kintla formation or Shepard formation. It is really hard to tell without a precise geologic map. At any rate, it is NOT Grinnell. The width of the rock in the foreground is ~ 70cm.
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Since we are at Boulder Pass, there’s also plentiful of typical Snowslip at the trail to Hole-in-the-Wall. This sample shows why the formation is called Snowslip (at least as far as I figure it). The glacial striations show what direction the “snow slipped.”
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Sometimes there are areas of low oxidation called reduction spots.
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As the red color of Grinnell formation is caused by oxides of iron, non-oxidized Grinnell has a different color: the greenish Appekunny tone or shades of orange. There are whole greenish beds of reduction within Grinnell. The cool thing is that iron content is roughly the same throughout the rock! GAME for you: What do you see when you look at this reduction zone?
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I see a very specific animal, and I know exactly what it is doing in there:
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It is a bunny rabbit, and he is looking for stromatolites, or so-called “cabbage heads”!

So what is a stromatolite? Did the bunny choose the right formation to dig in? If not, what formation would be better?

Read on.

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(Stromatolite layer along Going-to-the-Sun Road. The stromatolite layer is ~60cm high.)

Stromatolites are blue green algae or cyanobacteria that thrived on Earth in the Precambrian. The oldest stromatolite fossils on Earth are around 3.5 Ga. Stromatolites persist in the modern world in places where they are protected from grazing predators like snails. They were one of the first abundant photosynthetic organisms. They essentially remove CO2 from ocean; use the carbon for themselves while causing precipitation of calcium carbonate, and release the oxygen. They cover their cells with protective slime. When the slime gets too covered in sediment, they just grow a new layer, which results in dome-shaped layered “cabbage heads.” Stromatolites used to be so abundant that the sheer volume of oxygen they produced significantly changed the composition of our atmosphere. Stromatolites made our planet suitable for organisms like us!

Stromatolite beds are within many of Belt formations. The major stromatoliferous bed in Glacier National Park is the Helena formation. Some beds are in the Altyn and Snowslip formations also host stromatolites.

One of the best exposures of enormous stromatolites is at the Grinnell Glacier. Those honey-colored guys in Helena formation were ground down by the glacier so we can admire their cross-sections of their colony from the top. But first, a side view:
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Here is our little group hanging out with the Helena stromatolites.blogpostrockies2010-12 (Custom)

Notice the easily visible glacial striations!blogpostrockies2010-15 (Custom)

This awesome 1.8m diameter stromatolite cracked in half! blogpostrockies2010-17 (Custom)
In fact, this one was quite AGGRESSIVE, and had a DEADLY appetite.

Exposed at the Boulder Pass. Stromatolite in Shepard formation, as viewed from underneath. Stromatolites grow dome-shaped, but this is bowl-shaped. Therefore it is upside down. Field notebook for scale.
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This exposure near Hole-In-The-Wall cirque I named “Stromatolite Wall.” All those columns you see are stromatolites. The wall is some 8m high (exposed).
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Looking up the wall:
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This stromatolite weathered into a three-dimensional column! One can easily see the separate slime layers.
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Another absolutely stunning stromatolite bed is in the Snowslip formation. It is not a thick one, but special. The Snowslip formation was deposited closer to shore than the Helena, and the algae had trouble living there. There was quite some amount of organic material and mud periodically dumped in. Stromatolites caught the mud with its load of minerals into the slime layers, and those minerals later stained the fossils. The result: RAINBOW STROMATOLITES (my term). Next time somebody whines about how stromatolites are boring blue green grandpas, sitting around for billions of years doing nothing, just show them these playful buddies.
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Oh yeah! A close-up:
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One more (for good luck):
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Elsewhere in the Helena Formation, you can see halite casts:
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These are features that form when evaporation concentrates the dissolved Na & Cl ions so that they begin to bond together and crystallize salt. Later, when the water level rises again, the halite dissolves away and mud can fill in the empty cubic mold:
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There’s one more interesting feature in the Helena formation. OOLITIC LIMESTONE. I made it uppercase because most people don’t see this in the park. It is exposed just next to the Going-to-the-Sun Road in the western part of the park.
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In the photo, the gray beds are limestone, the brown ones are sandstone.

Oolites (also called ooids or ooliths) are little (0.25 to 2mm) round balls of limestone that for in warm shallow marine environments. The grain of limestone is gently rotated around by waves, and so the limestone precipitates in layers around the center…

If you look closely, you should see the oolites. They are ~0.5mm in diameter. Quarter for scale.
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Although Glacier National Park is primarily famous for its jagged glacial landscape (and for a good reason!), the rocks that make up its horns and arêtes are remarkable as well. Despite having been displaced ~50miles east, they retained many of their primary sedimentary features. It’s common to spot beautifully preserved ripple marks or mudcracks. The abundance of fossil algae – stromatolites – is striking as well. Glacier National Park offers arguably one of the best Belt rock exposures in the US, which also makes it extraordinarily colorful. The deadly combination of colorful strata, white snow, and jagged peaks ensures the park is the one of the most scenic places around. It is just gorgeous up there.

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Filip now leaves NOVA; my Rockies course this summer was his final NOVA class. Now he’s off to the University of Virginia. Good luck, Filip! –CB

A new river graphic

I really appreciated the feedback everyone contributed regarding the river evolution graphic I posted a week and a half ago. The latest offering is from Kyle House, who linked to a couple of nice summary images derived from Stanley Schumm. Because the images were low-resolution, and black and white, I decided to do some re-drafting. Here’s one (click through twice for full size version):

And here’s the original:

Images like this (and the previous, obsolete “river evolution” image) are central to the way I teach — a nice summary picture that compares variables. This one is more complex than I consider ideal, but I think it will do the trick.

I’d like to thank everyone who contributed to the discussion. I felt that this episode was a great example of how blogging benefits its practitioners. By putting my earlier graphic online, I got valuable feedback that corrected the erroneous and oversimplified way I was teaching about fluvial geomorphology. It was great to get critiques from both geomorphological and educational perspectives. That feedback has lead me to do some deeper thinking about that topic, and to change the way I teach it. Thanks – on behalf of myself and my future students!

Now for the new image… what would you critique here? (…either in terms of Schumm’s original ideas, or my redrawing of them…)

EDIT: Michael M. pointed out in the comments that several of the arrows were too low contrast to be legible. Funny, those colors totally aren’t what they looked like in the Corel Draw drafting stage! Anyhow, I’ve darkened them up a bit in this version:

River landscape evolution

I’ve developed a little cartoon diagram to show four stages of river landscape evolution. I use this image in Physical Geology when discussing how running water erodes the land. Check it out:

river evolution table

There are two rows, and four columns. The columns are the four stages of river landscape evolution: youth, maturity, old age, and rejuvenation. The rows offer different perspectives on the landscape: the upper row is a map view, and the lower row is a cross-sectional view.

The first two columns are shown here in more detail:

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When they are young, rivers ideally start out relatively straight in map view, entrenched in V-shaped valleys. You’ll also find plenty of waterfalls and rapids at this “Youth” stage. As time goes by, the river erodes downward to base level, and loses the gravitational impetus to incise any deeper. The river now begins to meander side to side, and as it does so, enlarges the size of its valley by lateral erosion at cut banks. It is “Mature.” As time goes by, the valley walls get further and further apart. …Then what?

river evolution table2

If enough time goes by, the river can enlarge the size of its valley so much that you can’t really tell it’s a valley any more. At this stage, meandering can get pronounced enough to fold back on itself and create oxbow lakes (visible in the map view of the “Old Age” stage). The story could conceivably end here. However, if base level were to drop anew, the river will begin to incise again, producing a valley profile (cross-section) that looks pretty much identical to the “Youth” stage. It has been made young again, or “Rejuvenated.” In map view, however, you can see from the meandering shape of the re-incised valley that the river must once have been at the “Old Age” stage. There are no more oxbow lakes in the “Rejuvenated” stage, as the river’s energy is going into downcutting rather than lateral meandering.

My experience is that this nice neat sequence works as a conceptual model for Physical Geology students. Nature, of course, is more complicated, but this serves me well as a foundational framework. What do you think? Is this scheme appropriate for an introductory audience, or is it too simple?

Strath vs. terrace graphic

There is an old Chinese aphorism that “the beginning of wisdom is to call things by their proper names.” One of the naming conventions that tends to trip up NOVA students who hike the Billy Goat Trail with me is the difference between a “terrace” and a “strath.” This morning, I created a graphic that illustrates the difference between these two landforms as I understand it:

strath_vs_terrace

Both features are shown in cross-sectional cartoon view. Terraces are cut into alluvium, the unconsolidated sediment deposited by the same river which is now incising. Straths, on the other hand, have the same shape but are etched into bedrock. Another name for straths would be “bedrock terraces.” Straths will sometimes have a thin veneer of alluvium atop them: in my experience along the Billy Goat Trail, this consists of abandoned bedload from older, higher base levels, augmented by lighter-weight flood deposits.

Would anyone with more geomorphological knowledge than me care to qualify / critique / correct my understanding on this terminological issue? Thanks in advance!

UPDATE: Based on Anne’s comments below, I’ve tweaked it a bit:

strath_vs_terrace2

Vector maps by Eric Fischer


“The Geotaggers’ World Atlas #8: Washington, DC” by Eric Fischer

If you like maps, you should go check out these images by photographer Eric Fischer. (via here) The different colors represent different modes of transportation: Black is walking (less than 7mph), red is bicycling or equivalent speed (less than 19mph), blue is motor vehicles on normal roads (less than 43mph); green is freeways or rapid transit.

Sistine Delta

Today’s imagery put me in mind of two hands reaching for one another:

sistine delta

What do you think? Shocking coincidence? Or a bit of a stretch?

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