This image, published earlier this week on NASA's Earth Observatory, reminded me that I haven't finished blogging up my time in the Adirondacks this summer yet:

Labels: mountains, new york, travel

The Crazy Mountains are a range of mountains in south-central Montana, north of Livingston:

In this Google Map, you can orient yourself from recent posts by finding Bozeman, the Gallatin Valley, and the Bridger Range down in the southwest corner.

The Crazys are an Eocene intrusion, (Ar/Ar dates of ~50 Ma), and they are beautifully expressed on a geologic map as a radiating series of dikes around two central blobs of intrusive rocks (quartz diorites, etc.: dark pink on the map):

These igneous intrusions penetrated the Livingston Group, a series of volcaniclastic sedimentary rocks of late Cretaceous to early Paleogene age (hot pink on the map).

The day before my students arrived in Montana this summer, Lily and I took a hike in the Crazys, entering in the northern part of the range. We saw some cool dikes exposed along the road on the way in. Here's me pointing out the contact between a subvertical dike of porphyritic andesite cutting across subhorizontal layers of the Livingston Group:


Annotated version of the same photograph:


And here's a close-up of the rock making up the dike; mostly fine-grained and gray, but with some lovely big euhedral plagioclase feldspars as well:


That's about it for the geology I saw in the Crazys. Our hike kept us mostly in the forest, so clearly I'm going to have to go back some other time and spend more time there!

Labels: igneous, montana, mountains, sediment, travel, volcano

After a post the other day, Michael wrote in to ask for clarification of "Pumpelly's Rule."

AGI defines Pumpelly's Rule thusly*: "The generalization that the axes and axial surfaces of minor folds of an area are congruent with those of the major fold structures of the same phase of deformation."

We saw some of this same idea expressed in yesterday's annotated photo series featuring parasitic folds on larger folded (and boudinaged) quartz veins. There were bigger folds there, and then those bigger folds were decorated with little parasitic folds. The idea behind Pumpelly's Rule is that you could get a sense of what the big folds are doing by looking at the little folds. But even more revealing than parasitic folds at the hinge area of a larger fold are the little folds that you sometimes see on the limbs of bigger folds.

Depending on the sense of the asymmetry of these folds, we call them either "S" or "Z" folds. The parasitic folds are more symmetrical towards the apex of the fold, but more asymmetrial along the limbs. Check out this diagram to see how small S-folds and Z-folds relate to the larger structure of the main fold. Blue arrows indicate the relative sense of shear on each limb of the main fold:


Pumpelly's Rule suggests that we don't need to see the whole picture to understand what's going on. Simply seeing the areas of the diagram highlighted in red are enough to give a sense of the bigger picture.

So how does that relate to this photo, which prompted the question?


Behind me in the photo, you can see an outcrop of the Cretaceous-aged Thermopolis Shale, exposed on Bridger Canyon Road, in the southern part of the Bridger Range, Montana. It has some sandstone layers in it. These sandstone layers, with their high color contrast against the surrounding black shale, record a series of lovely S-folds. The strata here dip moderately to the west. The S-folds relate the sense of shear on the larger structure of the Bridgers: they suggest that the bedding here is overturned, and that you're looking at the eastern side of a big north-south-striking anticline. In the southern Bridgers, therefore, the overall structure is an overturned anticline. Hiking west & uphill confirms this interpretation stratigraphically: as you go up, you go "back in time," encountering older and older strata: from the Thermopolis into the Kootenai, into Jurassic formations like the Morrison, the Swift, and the Rierdon.



Moral of the story: small observations can have large implications.

Raphael Pumpelly made this observation in 1894, presumably during his tenure as the head of the USGS New England Branch. Pumpelly sounds like he was an interesting guy, leading expeditions in Asia when that was a seriously sketchy prospect. In addition to his Rule, he is honored with a mineral named after him, pumpellyite.

* If you don't have a copy of AGI's Dictionary of Geological Terms, a good resource for looking things up online is this Dictionary of Mining, Mineral, and Related Terms sponsored by Hacettepe University in Turkey.

Labels: cretaceous, history, jurassic, montana, mountains, structure, websites

Working through my backlog of e-mails, I find that I have a few more Rockies course final projects to share with the world:

Laurie's website on Yellowstone geothermal features.

Jared explores Ringing Rocks.

Kevin suggests "more study is needed."

Ken discusses Grinnell Glacier:

Amanda reviews the Tetons:

Labels: glacial landforms, glaciation, montana, mountains, stromatolites, volcano, water resources, wyoming

Last week, I visited the Taconian Unconformity in the Catskills region of New York. I found out about the outcrop via the informative website the USGS put together in 2003 to explain southeastern New York's varied and interesting geology (Click here for a map).

Here's me at the angular unconformity, demonstrating the layering with my forearms:


Here's the same outcrop, sans goofball, avec annotations:


This is a classic angular unconformity. It even graced the cover of the (excellent) GSA publication Excursions in Geology and History: Field Trips in the Middle Atlantic States (Frank Pazzaglia, editor; cover photo by Marli Miller). Why should we care? Because like the "original" angular unconformity at Siccar Point in Scotland (described by James Hutton), this outcrop represents a lot of geologic time. First, during the Ordovician period, the Austin Glen formation had to be deposited as layers of clastic sediment in an ocean basin. Then, during the late Ordovician Taconian Orogeny, those layers had to be deformed: folded and buckled so they stood up on end, and then eroded down to their nubs. Then, on that newly-formed erosional surface, a fresh layer of sediment had to be laid down, in this case, the Rondout Formation was deposited as a layer of carbonate mud during the late Silurian period. Then, that too was deformed, during the Devonian period's Acadian Orogeny. Finally, the whole package had to be uplifted to the surface and exposed (in this case, when a highway roadcut was completed). That's a lot of time!

I'm delighted to have had the opportunity to visit it first-hand!

Labels: devonian, maps, mountains, new york, ordovician, silurian, structure, travel, unconformities

I made it to Lake Placid. It's raining buckets here.

Labels: mountains, new york

Good morning! I'm in New Paltz, New York, right now, on my way up to the Adirondacks for several days of fun, to be followed by a visit to a geologist pal in Drumlin Land, and then a quick excursion to visit some other friends in Canada. Later this morning I'll visit the Taconic angular unconformity outside of Catskill, New York. I'll try and post photos and whatnot as I go, in the same manner as yesterday's ptygmatic fold post -- my first ever remote post from the new iPhone. But I forgot to bring the iPhone charger, so we'll see how I do... Anyhow, stay tuned.

Labels: canada, mountains, new york, tech, travel, unconformities

Labels: california, glacial landforms, mountains

I just found out about the Appalachian Tectonics Study Group. They run a fun-looking weekender field trip each spring on topics of current research in Appalachian tectonics. I was not able to attend this year's event in the central Blue Ridge (due to the UMD petrology trip), but maybe I'll get to next year's event.

Labels: appalachians, field trips, mountains, plate tectonics

Almost a week after the field trip to Old Rag Mountain, and the Facebook-hosted pictures keep trickling in. Here's some shots by NOVA student Eileen Lodovichetti, and an ensuing discussion of feeder dikes and supercontinent breakup.

Here's a shot of the upper reaches of Old Rag, showing the characteristic spheroidal weathering of the Old Rag Granite and the relative lack of trees on top:

photo by Eileen Lodovichetti

...And here's a shot that Eileen took which shows the interior of one of the weathered-out feeder dikes we had to hike through on our way to the summit. You can actually see the classic geoprofessorial arm-waving caught in blurry motion!

photo by Eileen Lodovichetti

This is one of the coolest things about hiking Old Rag: after scrambling up on top of spheroidally-weathered granite domes, you drop into these tabular "hallways." The astute observer will note that the floor is made of a fine-grained, dark-green-colored rock, quite distinct from the light-colored, coarse-grained granite that makes up most of the mountain. These are dikes of metamorphosed basalt that intruded the granite during the breakup of the supercontinent Rodinia in the Neoproterozoic era of geologic time.

Here's one of my former Field Studies in Geology students, Mike Nelson, pointing out a similar dike along Skyline Drive, in the main part of the park:


Basically, the story goes like this: Around 1.2 to 1.0 Ga, continental fragments amalgamated into a supercontinent called Rodinia. In Virginia, this is recorded in the rocks of the Blue Ridge province, where the basement consists of granitoids (granites and related rocks) and metamorphosed granitoids (gneisses, mylonites). Among the youngest of these is the Old Rag Granite, which intruded the Pedlar Formation granite gness around 1.0 Ga.

Later, Rodinia broke apart, resulting in an extensional tectonic regime and mafic volcanism. Fractures opened up in the Old Rag Granite and funneled mafic magma towards the surface. Massive eruptions of basalt blanketed the landscape. The resulting layers of basaltic lava are known as the Catoctin Formation. At Old Rag Mountain, we can see some of the plumbing that led to these flood basalt eruptions: these are feeder dikes, because they "fed" the eruption above them.

Because the dikes (which were metamorphosed to greenstone during ~300 Ma Appalachian mountain-building) weather more rapidly than the Old Rag Granite, they are typically recessed into the landscape. That's what makes the "hallways" in the photograph above. Here's two more images, showing these weathered-out feeder dikes:



Check out how there's moderately-developed columnar jointing extending across the dike. These columns form perpendicular to the cooling front, and the dikes would have lost their heat out the sides. In horizontal lava flows, the heat is lost from the top and bottom surfaces, so you get vertical columns. Here, a vertical dike produces horizontally-oriented columns. Hikers appreciate these "steps" as they squeeze through the dikes on their way up the mountain.

Here's a map of part of Shenandoah National Park:


Please ignore the "hover" instructions at the lower right. I've reproduced the "hoverable" image below. Key: the orange is the Pedlar Formation. The pink is the Old Rag Granite, and the green is the Catoctin Formation. Feeder dikes of the Catoctin are shown as green lines.

Now, let's take away the map, and just preserve the orientation of the feeder dikes. This will tell us the overall tectonic stretching direction:
Various plate reconstructions show either Amazonia or the Congo craton offboard of Virginia at the time Rodinia broke apart and the Iapetus Ocean began seafloor spreading. I've illustrated it here as the Congo, but that might be wrong.

So: the hike up Old Rag is great exercise, and offers scenic views, but for those willing to consider the rocks and how they got there, it's an insightful view into the tectonic past.

Lastly, here's a lovely, well-developed weathering rind on the Catoctin meta-basalt (greenstone). When the dark green rock adjusts to the conditions at the Earth's surface, it breaks down, resulting in the tan/"buff" color on the outside. You're watching the rock "rot" from the outside surface, working its way inward:


More on the geology of Shenandoah National Park can be seen at this page on my website.

Labels: appalachians, basalt, blue ridge, field trips, metamorphism, mountains, national parks, nova, plate tectonics, shenandoah, structure, weathering

Last weekend, I took a group of students, mostly from NOVA but also 3 from GMU, up to hike Old Rag Mountain in Shenandoah National Park.

Here's a Google Map showing the terrain (and trails, which is a cool new addition to the already cool Google Maps):


The crew discusses debris flow deposits in the forest on the way up the mountain:

photograph by Charlie Corrick

The first spot where we get a nice view out over the valleys below:

photograph by Charlie Corrick

Spheroidal weathering in Catoctin Formation greenstone:

photograph by Jared Fortner

Spheroidal weathering in granite (the Old Rag Granite, 1.0 Ga):

photograph by Charlie Corrick


photograph by Charlie Corrick

Student Jared atop a spheroidally-weathered boulder of the Old Rag Granite:

photograph by me

Grain-size differences in the Old Rag Granite (balanced atop my leg):

photograph by me

Non-foliated Old Rag Granite (showing lovely "blue quartz"):

photograph by me

And the foliated version of the Old Rag Granite:

photograph by me

Labels: appalachians, basalt, blue ridge, field trips, geology, granite, igneous, mountains, national parks, nova, structure, weathering

Yesterday, four Honors students and I went out to West Virginia's route 55 (between Wardensville and Moorefield), to look at some sedimentary strata and associated tectonic structures. Our guide was my friend David Dantzler, an enthusiastic amateur geologist. Here's a map of the terrain we traversed:



As you can see, this is part of the Valley & Ridge province, an area of the country defined by Paleozoic rocks that were folded and thrust-faulted during the Alleghenian phase of Appalachian mountain-building. Recently, a new road has been constructed traversing these valleys and ridges. It's a bit of a boondoggle, a pet project of West Virginia senator Robert Byrd which funneled federal dollars into the Mountain State, ostensibly to make it easier for the chicken farmers of Moorefield to get their birdie bits to market on the east coast.

This image ought to give you a sense of the project's scale (big bridge), and how much use it gets (no one on the bridge):


But the U.S. taxpayer's loss is the geologist's gain... There are some pretty spectacular new exposures of Valley & Ridge rocks along the new route 55. Here's the NOVA van parked at an outcrop of Tuscarora Sandstone that is arched up into a broad anticline. Again, notice how few people are driving on route 55 here:


Ooh, look: heavy traffic!


Contact between the lower Tuscarora Sandstone (a Silurian-aged extremely pure quartz sandstone, variably fused to quartzite), and the overlying (darker-colored) formation, which is either the Rose Hill Formation or the Mackenzie Formation at this location:


We found oodles of cool trace fossils:







But it wasn't just sedimentary layers. There were also some cool tectonic structures, like this joint in the Tuscarora, showing a beautifully developed hackle fringe:



Here's some "pencil cleavage" where fine-grained shale develops cleavage that intersects the planes of fissility, causing it to fracture in long slivers:



I slammed on the brakes for this one: an awesome anticline...


I forced David and the students to act out the orientation of the bedding planes at this anticline:


Honors student Jason points out a small thrust fault in the outcrop above him: You can see the offset in a greenish/gray shale layer:


In case it wasn't obvious above, here's a zoomed-in shot, with the offset layer highlighted (the miracles of Photoshop!) and the fault labeled:


We all had a grand day outside, and the rain held off until our return trip, which was pretty great. Thanks to David for showing us these rocks, and thanks to my students for being smart and inquisitive and into field trips.

Labels: appalachians, devonian, field trips, fossils, mountains, nova, politics, primary structures, sediment, silurian, structure, teaching, valley and ridge, west virginia

For the penultimate post in my Ecuador travel series, I hereby recount the story of climbing the mountain called Iliniza Norte (16,997 feet above sea level: the tallest peak I've ever summitted).

We began by driving up from the town of Chaupi, where we were staying at a hostel, to the trailhead above treeline in the paramo ecosystem...


We had hoped for awesome weather, but as with our previous peak bagging in Ecuador, the clouds were here too, making a ceiling that we headed up into...




Heading up into the clouds; the valley below fades away...


...and we start to see snow.






We went up a long, steep snowfield for probably two hours... It was frustrating going: take one step forward, slide two steps backward. The snow got thicker and thicker...

Eventually, when we got close to the summit, we got off the snowfield and onto some rocks. I was surprised to feel how my energy spiked at the prospect of rock-scrambling. The long slog up the snowfield was boring and repetitive, but this was totally engaging as a physical/mental workout. Here's Lily and Diego climbing up:



At the summit, there's a steel cross with various doodads attached...


This is the highest point above sea level I've ever experienced. When I stood on the summit, my head was above 17,000 feet in elevation!



Silly video of the summit team making celebratory noises:


Then Diego said, "I think we go down now, because of thunders."

The guy knows his stuff: as soon as he had said this, we heard a ba-boom from off in the white clouds somewhere... Yikes. Okay, time to head down.

Descending the rocks:


When we got to the snowfield, another peal of thunder sounded, and this one was louder than the first one. The snowfield, fortunately, made for easy going -- we essentially skied down it. It was pretty exciting... Flashes of lightning, booms of thunder (sometimes within a microsecond of one another), adrenaline pumping, running/sliding/skiing downhill as fast as we could.

We did not get hit by lightning.

After we got below cloud level (and into a valley where we felt a little less exposed to lightning strikes), we could see that the lower elevations had gotten some frozen precipitation too: a mix of snow and hail:











When we got back to the vehicle, we found it covered in hail:


Now for the adventure after the adventure: driving down a steep, twisting, muddy mountain road that's coated with hail and host to numerous roaring streams of runoff. It was almost as intense as descending the snowfield amid lightning bolts: the vehicle slid and knocked against a mud embankment at one point, and it was all seriously sketchy. Diego said he had never seen anything like it.

Here's some video of a raging torrent of meltwater/runoff flowing over a road surface that's decorated with white hailstones:



We did not crash the car.

Back safely at the hostel, we took hot showers and drank beer and congratulated ourselves for clearly being such daring adventurers. Whew... the next morning, we took our weary selves back to Quito.

One more Ecuador post to go... on lichens... stay tuned.

Labels: ecuador, ice, mountains, snow, south america, travel, volcano

As you'll recall, when I left off with my Ecuadorian travelouge, Lily and I had summited Pasochoa, and then taken a day-hike in Cotopaxi National Park. Next up, a new mountain that has about the same elevation as Mt. Whitney (highest peak in the lower 48 United States): about 14,500 feet. To climb this extinct volcano called Ruminahui (Roo-min-ya-wee), we headed up a ridge between two adjacent glacially-carved valleys.















Me with clouds and background glacial valley:


Diego (our guide) on the trail:


Up on top, there was less vegetation, but more cloud... and snow was falling.

The bedrock was a volcanic breccia that had been cut by numerous andesitic dikes:






You can see some blurry snowflakes in the previous photo. Here's a cold-looking Lily with her boots on an andesitic dike:



Here's a couple of close-ups to show the cross-cutting relationships between the andesite dikes and the volcanic breccia:





Here's a short, not-especially-great video wherein I point out a few things that don't really show up all that well. Still, you get to see it snowing!

A big "thanks" to NOVA's king of digital video, Richard Attix, who helped me rotate this video and crop out some unintended footage from the raw video we shot on the mountain that day.

Cold hikers:



"Sheesh! It's cold up here!":



On the way down, we also took some time to check out the plants. Here's one called "Orejas de conejo" ("Ears of the rabbit"):

Here's one that smells exactly like chocolate!


In fact, Lily was able to harvest this chocolate bar from it!

Okay, not really. It's money that grows on trees, not chocolate bars.

So that's the story of our second successful summit... now there was only one more to go... the legendary Iliniza Norte. Photos from that hike in a couple of days...

Labels: ecuador, glacial landforms, mountains, plants, sediment, south america, travel, volcano

Yesterday I mentioned finding a new (to me) outcrop of the Martinsburg Formation's graded beds (turbidite sequences shed off the late-Ordovician Taconian Orogeny here on the east coast of North America). Today, I'd like to share a few images of where John Graves and I went next: up into the heart of the Massanutten Synclinorium, the Fort Valley. To remind you of the relationship between the Shenandoah and Fort Valleys, here's a Google Map I've posted before:



There, defining the ridges of Massanutten Mountain (and thereby separating the lower Shenandoah Valley from the upper Fort Valley) is the Massanutten Sandstone, a Silurian-aged quartz sandstone (in some places it's a quartz-pebble conglomerate) that is correlated to the Tuscarora Sandstone further west in the Appalachian Mountains' Valley & Ridge province.

The Massanutten can show some nice primary structures, including some of the oldest known terrestrial plant fossils (preserved as fragmentary carbon films) and cross-bedding like this:



With regard to the cross-bedding, note that this is "reverse" cross-bedding, which records shifts in current direction over time. At the bottom of the sample, the current was flowing from left to right, and at the middle and top of the sample, it was flowing in the opposite direction, right to left. This sample shows well the distinctive shape of cross-beds: they are tangential to the main bed at the bottom, but are often truncated on top, making them superb geopetal indicators. (They tell you whether your rock is right-side-up or up-side-down.)

I took John on a hike up the Veatch Gap trail, because I wanted to show him the awesome anticline in the Massanutten Sandstone that NOVA adjunct geology instructor Chris Khourey and I had found on a reconnaissance trip out there in May of last year. John and I took a "group shot" with the fold:



And here's John showing those Montanans that we do actually have some cool geology out on the east coast:



So, what's going on here? Well... the Valley & Ridge province of the mid-Atlantic region is defined by folded (and thrust-faulted) sedimentary strata. These folds were produced about 300 to 250 million years ago, during the Alleghenian phase of Appalachian mountain-building. The tectonic cause of this deformation is interpreted to be North America's collision with Africa, closing the Iapetus Ocean and completing the assembly of the supercontinent Pangea.

More locally, the Shenandoah Valley and Massanutten Mountain are structurally underlain by a great fold, the Massanutten Synclinorium. Synclinoria are different from mere synclines because they are more complicated: the overall synclinal shape is "decorated" with numerous smaller anticlines and synclines. It's a big trough-like shape, but wrinkles are "parasitic" on the main fold. So, even within the big "canoe" shape of the Massanutten Synclinorium, there are little bulges and wrinkles that go the opposite direction. This anticline is one of them.

At that point, having seen the anticline, we weighed whether to keep hiking or not.

We opted to press on... and I'm so glad we did. ... Twenty feet further down the trail, we saw another two anticlines!



At its base, this one had a small cave I could crawl into:



And: a short distance further we found a hiker's shelter with an apt name:



Ha! I love it.

More tomorrow, when I'll revisit the issue of plumose structure and hackle fringes.

Labels: appalachians, geology, mountains, msse, ordovician, primary structures, sediment, silurian, structure, valley and ridge, virginia

Yesterday, I mentioned what my MSSE advisor John Graves and I saw along the Billy Goat Trail on Saturday afternoon. Today, I'd like to share some images and insights from our Sunday field trip, out to the Shenandoah Valley and the Massanutten Synclinorium which underlies it.

I would like to thank Rick Diecchio of George Mason University for sharing some key outcrop knowledge with me. I've found that information about good outcrops can be very difficult to obtain unless you know somebody who knows. The information is primarily passed on through the oral tradition, rather than written in sufficient detail in peer-reviewed literature or in field guides (...or posted on geoblogs?).

Anyhow, back in December, on our drive down to the Blue Ridge / Valley & Ridge Symposium in Charlottesville, I told Rick I was organizing a new Massanutten Synclinorium field course. It's a place he's very familar with. He recommended a good outcrop to see the turbidite sequences of the Martinsburg Formation, a late Ordovician clastic unit made of debris shed off the rising Taconian Mountains to the east. Rick drew me a map in my field notebook, and on Sunday I was finally able to schedule a visit. Since John is unfamiliar with the stratigraphy and structure of the Shenandoah Valley (or the east coast in general), we also stopped at a lot of the other stops I'll be taking students to, including the classic "Tumbling Run" section.

Today I'd like to share a sets of photos with you from this new (to me) outcrop of the Martinsburg Formation. Tomorrow I will share another set from the next layer up in the stratigraphic stack, the Massanutten Sandstone. Both outcrops a pleasing combination of sedimentary stratification and structural geology.

Here's the Martinsburg Formation outcrop, just west of the Shenandoah River's North Fork:


This, like the "Pet Store Anticline" that I have previously blogged about, is an excellent place to look at bedding/cleavage relationships. The beds are dipping east, but the cleavage dips steeply to the west, implying the outcrop's position within a much larger (kilometers-wide) cleavage fan.

Here's a eye-catching outcrop that shows the beds weathered out differentially, while pervasively cut by ~vertical metamorphic cleavage:


More beds, of alternating sand and mud, steeply dipping in the Massanutten Synclinorium:

Note how the muddier portions show cleavage development better than the sandier strata.

More pervasively-cleaved muddy layers:


Here's one that confused me. In this predominantly-sandstone layer, you can see that the cleavage is better developed on the right, lower side of the bed. Does this mean that the right, lower-side of the bed is more mud-rich? (and sand-poor?) It did appear to be finer grained. If so, does this imply this bed is upside-down? Ordinarily, I would have thought to only look for the primary sedimentary structure as a geopetal (right-side-up) indicator, but this is the first time it has occurred to me that structural susceptibility based on mineralogy (in this case, susceptibility to cleavage development) could be used as an indicator of younging direction. I should note that this particular photo was taken downhill of the main outcrop, and may well be overturned. It's a synclinorium, after all, not a smooth syncline!


In this photo, the turbidite sequences of the Martinsburg Formation show a cool feature, a primary sedimentary structure known as cross-bedding:

Note that this photo is taken with the photo's long axis ~parallel to bedding, but the reality of the outcrop is that this is all steeply dipping, rotated 90 degrees clockwise (see the inset for "true" outcrop orientation).

...But wait! There's stuff dipping to the left, and stuff dipping to the right! Which one is this purported cross-bedding? Try this labelled version to sort it all out:

Note how at the bottom, the cross-beds curve tangentially to subparallelism with the main bed. They are truncated at top by the overlying layers. This is a good geopetal indicator, and the photo is oriented in depositional position, with the top at the top. Furthermore, if you reconstruct the current direction from these cross-beds (after the strata have been "unfolded" and restored to their original horizontal orientation, it would have come from the east... that is, from the orogen itself (the roots of which are exposed along the Billy Goat Trail.)

The intersection of rock weaknesses along the planes of bedding and planes of cleavage can result in the rock fracturing into long pencil-like bits, a phenomenon known as "pencil cleavage." This is my Freddy Krueger impersonation using the Martinsburg's cleaved "pencils."


John puts his hand up to give a sense of scale to the axis of this small fold in the steeply-dipping strata:


I was all agog over this outcrop, really digging the relationship between the structure and sedimentological elements in the rock. Best of all, it's a very short drive from Tumbling Run, and will replace the hike to the Buzzard Rock outcrop in my Massanutten field trip in April. (For NOVA-area readers, there are still four spaces open in that class...)

Labels: appalachians, mountains, msse, ordovician, primary structures, sediment, structure, valley and ridge

Meme bait! Here's the tallest points in each of the 50 United States, with Puerto Rico's and Washington, DC's highest points thrown in for good measure. Elevations are in feet above mean sea level. I've bolded the ones I have personally stood atop:

Cheaha Mt., Alabama 2,405'
Mt. McKinley (Denali), Alaska 20,320'
Humphreys Peak, Arizona 12,633'
Magazine Mt., Arkansas 2,753'
Mt. Whitney, California 14,494'
Mt. Elbert, Colorado 14,433'
Mt. Frissell, Connecticut 2,380'
Fort Reno, Washington, DC 429'
Ebright Azimuth, Delaware 448'
Britton Hill, Florida 345'
Brasstown Bald, Georgia 4,784'
Mauna Kea, Hawai'i 13,796'
Borah Peak, Idaho 12,662'
Charles Mound, Illinois, 1,235'
Hoosier Hill Point, Indiana 1,257'
Hawkeye Point, Iowa 1,670'
Mt. Sunflower, Kansas 4,039'
Black Mt., Kentucky 4,139'
Driskill Mt., Louisiana 535'
Mt. Katahdin, Maine 5,267'
Backbone Mt., Maryland 3,360'
Mt. Greylock, Massachusetts 3,487'
Mt. Arvon, Michigan 1,979'
Eagle Mt., Minnesota 2,301'
Woodall Mt., Mississippi 806'
Taum Sauk Mt., Missouri 1,772'
Granite Peak, Montana 12,799'
Panorama Point, Nebraska 5,424'
Boundary Peak, Nevada 13,140'
Mt. Washington, New Hampshire 6,288'
High Point, New Jersey 1,803'
Wheeler Peak, New Mexico 13,161'
Mt. Marcy, New York 5,344'
Mt. Mitchell, North Carolina 6,684'
White Butte, North Dakota 3,506'
Campbell Hill, Ohio 1,549'
Black Mesa, Oklahoma 4,973'
Mt. Hood, Oregon 11,239'
Mt. Davis, Pennsylvania 3,213'
Cerro de Punta, Puerto Rico 4390'
Jerimoth Hill, Rhode Island 812'
Sassafras Mt., South Carolina 3,560'
Harney Peak, South Dakota 7,242'
Clingmans Dome, Tennessee 6,643'
Guadalupe Peak, Texas 8,749'
Kings Peak, Utah 13,528'
Mt. Mansfield, Vermont 4,393'
Mt. Rogers, Virginia 5,729'
Mt Rainier, Washington 14,410'
Spruce Knob, West Virginia 4,861'
Timms Hill, Wisconsin 1,951'
Gannett Peak, Wyoming 13,804'

A good map and comprehensive list of these high points can be found at geology.com. Which ones have you visited?

Labels: mountains, travel

I went to Ecuador to climb mountains.

After a lovely two days of recovery in the thermal springs of Papallacta, Lily and I began our mountain-climbing tour. We summited three peaks in the central Ecuadorian Andes: Pasochoa, Ruminahui, and Iliniza Norte. Today I'd like to share our experiences climbing the first (and shortest) of those, the peak called Pasochoa. Here it is from the rough road we drove in on:



From a Google Maps perspective, here's the physiography of the surrounding area. Pasochoa is the highest peak of the central volcano in this view:



Once we started hiking, we got above the trees and into the paramo ecosystem, a high-elevation grassland biome that exists between treeline and the bare rocks above where only lichens survive. Another view of the peak, which is about 13,700 feet in elevation:



Once we got up a little bit, we could look down to the Valle de los Chillos, a massive valley between Andean peaks, south of Quito:



One of the most spectacular things that happened on this hike is we saw an Andean condor, which flew by between us and this view, quite spectacularly. We weren't able to get the camera out in time to capture it, but with its black and white plumage, it was unmistakeable. Here's a amateurish Photoshop to show what it kind of looked like:



I pointed out the volcanic breccia to Lily and our guide, Diego:



More of the same could be seen in eroded-out minarets on the flanks of the mountain:




Pasochoa is one tall bit along the rim of a much larger caldera, and when we got up to the edge of that caldera, we got a real sense of its sudden drop-off. Clouds/fog curled up and over the lip, obscuring the view, but we could peer down into them and see that the land dropped steeply away for many hundreds of feet.



Lily gives a sense of scale to the edge of the caldera:



After lunch on top, more clouds moved in, and we decided to decamp back to the vehicle. Here's Diego and I descending the trail towards lower elevations.



Being a guy who had just recently recovered from something akin to pneumonia, I felt pretty good about making the summit of a 13,700' peak. Next up: let's see if we can't find something a little bit taller...

Labels: birdies, ecuador, mountains, south america, travel, volcano

Another artifact from my days as a boy scout...



I'm in the back row, third from the right. Sixteen years old.

The mountain in the background is the Tooth of Time.

Labels: mountains, new mexico, travel

This is from the tour operators in charge of me this week...
-CB

Day 01. Quito - Pasochoa
Pick up in your hotel. we depart from Quito at 09h00 in the direction to Volcano Pasochoa, where your trekking begins. As you walk up hill towards it summit (4200m) you will enjoy the views of the neighbours peaks such as Antisana, Rumiñahui and Cotopaxi. You will head south on a easy going trail along the crater edge of this extinct volcano, Condors and other birds of pray are often seen before you descend in a green valley. We arrive in a Aclimatization Center Tambopaxi is located at 3200 m. a refugee in the middle of Cotopaxi and Ruminahui volcanoes.

Day 02.- Limpiopungo, at the base of the Cotopaxi Volcano
Today you will explore the Paramo of the Cotopaxi National Park. Here you will visit the Pre-Inca ruins of El Salitre while enjoying magnificent views of Cotopaxi Glaciers. Afterwards you will continue to Limpiopungo valley and lake. Return. Dinner and overnight.

Day 03.- Climb. Ruminahui & Limpiopungo Lake
Today is the longest day of your trekking tour. You will walk along a trail, up and down following the flanks of Ruminahui peak observing birds of prey and in the horizon the mighty Chimborazo, and Illinizas. Return to Limpiopungo where we dirve to the Cuello de Luna. Dinner and overnight.

Day 04.- Illiniza Ecological Reserve
Drive to the north following the route Illinizas reserve until arrive to la Llovisma, another acclimatization center. Overnight.

Day 05.- Climb Illiniza North - return to Quito
Today you can either drive to the parking place of the Illinizas and walk uphill to the settlement of Illinizas and summit the north peak which is rather easy and recommended as training for those who will attempt Cotopaxi. Somewhere in highlands, your vehicle will be waiting to transfer you back to Quito.
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Here's the view of Illiniza Sur from Illiniza Norte:

Oh, yeah....

Labels: ecuador, mountains, south america, travel

What's the tallest mountain on Earth? Most would say Everest, since it's the highest point above sea level. I mentioned this issue as part of my lead-in to my Mauna Kea post, since some folks might claim Mauna Kea as the tallest, since it rises the most above its base on the oceanic crust of the Pacific Plate. But there's a third contender: Mount Chimborazo, in Ecuador.

The planet Earth is not a perfect sphere; it bulges a bit at the equator (about 13 miles) compared to the poles. The result is that if you look at two mountains of exactly the same elevation, one located at the pole and one at the equator, the equatorial one will be 13 miles further away from the center of the Earth than the polar one. That makes the peak of the tallest equatorial mountain (Chimborazo is at ~1.5 degrees south) the point on Earth that is furthest away from the center of the planet. It is 1.3 miles (2.1 km) further away from the center of the Earth than the summit of Everest is. NPR covered this surprising statistic in an entertaining piece in 2007. However, as the commenter on this post-NPR post notes, it's not just the silicate earth that bulges at the equator, it's the atmosphere, too. So it's not like the air is thinner at Chimborazo than Everest. You may be closer to the Moon atop Chimborazo, but you're not closer to "space" due to all that extra thick atmosphere above your head.

Here's a Google Maps "terrain view" map of Chimborazo (high relief peak east of El Arenal):


I had hoped to "auto-post" this while I'm traveling in Ecuador, for about the same time I would be looking at Chimborazo with my own eyes. However, I got sick over the holidays, and the persistent illness forced me to change my travel plans. I'll still be going to Ecuador -- but only for one week instead of the planned two. And I still hope to catch a glimpse of Mount Chimborazo. Hopefully when I get back to DC, I'll be able to share some photos of this superlative mountain. For now, the map will have to do.

Labels: ecuador, maps, mountains, south america, travel, volcano

What's the tallest mountain on Earth?

Everest, right? Well, yeah: if you're measuring from sea level. If you're measuring from the top of the crust the mountain rises from though, it's Mauna Kea, Hawai'i. It's about ~13,800 feet above sea level, but it rises ~33,500 feet from the oceanic crust to the peak (that's compared to Everest's mere ~29,000 feet from base to peak. So... you could say that Mauna Kea is the tallest mountain on our planet... (you could!)

On Thanksgiving day, my friend Lily and I took a drive up to the top of Mauna Kea, and did a little hike up there at high elevation. Today, I'd like to share some photographs of that excursion. We saw some pretty cool geology.

On the drive up the mountain, we saw an animal which was apropos, considering the day:

Gobble, gobble, gobble. Watch out turkeys, we'll be back after we work up an appetite...

Here's Lily's jeep in the "saddle" between Mauna Kea and Mauna Loa, looking north (with Mauna Kea in the background and basaltic lava flows from Mauna Loa in the foreground):


Some cider cones (the Hawai'ian word for cinder cone is pu'u) in the saddle:


Turning the other way (looking south), you can see the bulky form of "the long mountain," Mauna Loa. What a classic shield volcano shape! I love the fact that it's so dang wide it makes a lousy photograph. You just can't capture its spread-out bulk in a photo; it's too massive:


This was the spot where I pretended to have my toes overrun by a pahoehoe flow:


As we drove up the road to the top of the mountain, I was amazed at the raw volcanic landscape, decorated with cinder cones like this one:


At one point, we passed a neat little angular unconformity on the roadside. Here it is, with a nickel (white dot left of center) for scale:


Here's a closer-shot of this small angular unconformity. Earlier layers of ash and lapilli were deposited at a steep angle, and then eroded (perhaps by glaciation? pure speculation there) before more ash and lapilli were deposited atop it, at a lower angle. There's not likely to be much time missing here, and so perhaps it's better to think of this as the top of a cross-bed, an advancing front of pyroclastic deposition moving down the mountainside, overrun by later eruptions, which may have scoured off the upper few inches (??? pure speculation) or so before deposition.

Really, the truncated tops of cross-beds are mini-angular-unconformities, when you think about it; just not with the same amount of time missing at a "real" angular unconformity (with millions of years missing) due to mountain building like the one at Siccar Point. (Video of cross-beds forming)

Here's something else which the clueless geologist might mistake for a sign of mountain building:
No, those aren't originally-horizontal strata that have later been folded. They're layers (again of ash and lapilli) deposited on the originally-rough topography of the mountainside, covering small ridges and filling small valleys. Where a given layer is exposed at higher elevation, I interpret to be a paleo-topographic high; where that same stratum is exposed at lower elevation, that's a paleo-topographic low. The roadcut reveals these layers have undulating shapes, but this is unlikely to be folding that results from tectonic compression: instead, I think it's showing us the lay of the ancient land surface.

Looking south, we could see past Mauna Loa to the actively erupting steam vent coming out of Halemaumau Crater at Kilauea Caldera (source of the vog!):


Near the summit of Mauna Kea, there are a bunch of astronomical observatories:






On the summit is where you find those examples I mentioned the other day of hawaiite, a rock of basaltic composition that is very dense (ostensibly due to erupting beneath the extra pressures of a Pleistocene ice cap):


Here's me on the summit:


View to the north from the summit: More cinder cones...


Here's a YouTube video of me pointing stuff out from the summit (Kilauea, Hualalai, Mauna Loa, observatories, hikers, etc.). Unfortunately the wind makes it all but unintelligable, but I filmed it, doggone it, so I'm going to post it:



I found a beautiful example of a volcanic bomb up there:


After the visit to the summit, we went for a hike to a small supposedly-glacially-gouged-out lake below the summit (Lake Waiau):


Here's a Google Map, showing the lake's location:


I was surprised to see a thick biofilm on the bottom of the lake:


Encrusting the pebbles and cobbles there, it reminded me of Nora Noffke's modern and Archean biofilm photos in the recent GSA Today, as well as my "Life in Extreme Environments" class this past summer at Montana State University.


We saw some nice examples of structural geology on this hike. Previously, I've mentioned plumose structure, a branching pattern on the topography of fracture surfaces in fine-grained rocks. We saw some of that on blocks of basalt atop Mauna Kea, as in this example (again a repeat photo, but the other day I showed it to you for the vesicle; today I'm showing it to you for the plumose structure.)


A similar feature are arrest lines, which again are minute variations in the surface of a fracture. Like plumose structure, which branches from a source point (where the fracture initiated) and branches out in the direction of propagation, arrest lines tell us about the development of a joint. Unlike plumose structure, though, they are not parallel to the propagating fracture front. Instead, they form perpendicular to it, and record how the fracture propagates in small "steps." Each of these arrest lines is interpreted as being a spot where the fracture grew a little bit, then stopped ("arrested") and then grew some more. In this case, the fracture face we're looking at started at the bottom of the picture and grew towards the top of the photo. You can even see some less-discernible plumose structure backing this up:

Similar arrest lines can be seen in basalt images here and here...

We also saw some pretty spectacular xenoliths. Here's one of gabbro in basalt:


Here's one of peridotite in basalt:


And a few more:



My boots, with another volcanic bomb:


Driving back down the mountain afterwards, we got this nice view of the cinder cones (pu'us!) in the eastern part of the "saddle" between Maunas Kea and Loa:


This Mauna Kea excursion was one of my favorite things that I did on my all-too-brief trip to Hawaii. It was great to get up in the high country, where the air is thin (and vog free!) and the skies are deep blue, and the geology is surprisingly varied (at least it was surprising to me, and pleasantly so). The hike let us work up a good appetite, so we headed back down the mountain and straight to Thanksgiving dinner!

Labels: basalt, birdies, geology, glacial landforms, hawaii, igneous, mountains, msse, primary structures, structure, travel, unconformities, volcano, xenoliths

This image came to my attention the other day via Lutz's Geoberg blog. It's one of the high-res images provided by the newly-launched satellite, the GeoEye-1, which is supplying new images to Google*. The image shows a marginal lake associated with an alpine glacier in Kenai Fjords National Park, Alaska (just south of Seward):


The top of the above image is not north; it's southwest. Mentally rotate it, and you can see that the resolution is a lot better than the current level on Google Earth and Google Maps:


The thing that struck me about the new GeoEye image, aside from its beauty, is the distinct pattern of iceberg sizes in the lake: freshly calved off the glacier, the biggest icebergs are close to their source, while further away the icebergs are smaller. This pattern struck me as being analogous to sediment. Fresh from its source, sedimentary particles are at their largest size, and the further away they travel, the more weathering they experience. This weathering (in particular of the physical variety) tends to break them down into smaller pieces. Adjacent to an orogenic belt, for instance, you tend to find deposition of sedimentary particles shed off the uplifting mountains. As a general rule, these are of the largest sizes and the greatest volume closest to the source, and then particle size and stratum thickness both diminish with increasing distance from the orogen.

For a North American example, consider the Catskill Clastic Wedge, a tick pile of sediments shed off the late Devonian Acadian Orogeny along the east coast. Here's a cross-sectional view** (pre-Alleghany Orogeny deformation) of the wedge, running from the Bay of Fundy west to Michigan:


Same pattern! Coarse stuff, and more volume of stuff, close to the source. Finer stuff, and less volume of stuff, further from the source. Just like the iceberg, except the weathering of the icebergs is mainly thermal, while the weathering of the sediments is physical, accompanied by depositional sorting by the transporting currents of water.

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* An original version of this post misidentified Google as the owners of the GeoEye-1, as opposed to the company called GeoEye, which sells images to Google. Thanks to Bruce Haley for the correction. (updated 8:14AM eastern time on Dec. 9, 2008)
** Image redrawn (by me) from an original in Prothero & Dott (2003).

Labels: alaska, analogies, art, canada, glacial landforms, glaciation, maine, michigan, mountains, new york, satellite imagery, sediment

My friend Noah is a photographer on a Fulbright scholarship in Malaysian Borneo. He shared this photo with me yesterday... a spectacular image from the top of Mount Kinabalu (the fourth-tallest mountain in southeast Asia). With his permission, I'm sharing it with you, too:



For more of Noah's photography, check out his website: Hope in Light.

Labels: art, malaysia, mountains