Posts Tagged ‘earthworks’

Icons of Plate Tectonics

3 November 2011

30 years ago, yesterday, I started breathing. 101 years before that, dude on the left, Alfred Wegener, showed up* which seems as good a reason as any to throw up a post that I have been meaning to put together forever.

Nearly every contemporary introductory geology or paleontology textbook–usually right next to the passing mention of Wegner’s frigid death collecting weather data on a Greenland glacier–reproduces some version of this figure:

It is a fantastic picture, one that helps to demonstrate one classic piece of evidence that helped to seal the paradigm shift of plate tectonics. It can be employed to address general concepts like the utility of fossils for addressing broader geologic questions; or to illustrate the actual relationship of the continents approximately 250 million years ago when most of the world’s landmasses were assembled into the massive supercontinent of Pangea.

It made several appearances in my History of Life and Paleobiology lectures this summer.

But there is something about it that has always bothered me: it’s totally bogus.

Well perhaps that is overstating it a bit. The nested ovals and zig-zags purport to show the distribution of several key Gondwanan fossil taxa across the landmasses that now constitute South America, Africa, Asia, India, Antarctica and Australia. The ranges of these species–terrestrial or freshwater plants and animals unlikely to cross major ocean barriers–strongly suggest that the southern continents were long ago connected permitting easy movement between land masses today separated by oceans. The fact that these fossils range from Permian to Triassic in age even gives us an approximate time range for this continental configuration.

But scrutinizing the actually ranges shown in the picture some problems arise. Mesosaurus–something of a poster-fossil for plate tectonics–has been found in Africa and modern day Brazil this map places it in Argentina. Cynognathus on the other hand is known from South Africa, Argentina and Antarctica, while this map appears to show it in Peru and central Africa. Glossopteris has been found across much of South America, India, Africa, Antarctica, Australia and beyond, however this map shows it in a very narrow zig-zag belt across these continents. One version of the figure maintains the overall shapes, but juggles the labels to bring it slightly more into accord with reality.

So what gives?

The map has its origins in a figure printed in Wandering Lands and Animals (1973) written by Edwin Colbert:

Colbert was one the paleontologists that uncovered the Triassic fossils in Antarctica represented in the figure. Clearly the map is meant to be diagrammatic, illustrating, as the original caption states “the paleontological links that bind it [Gondwana] together,” rather than a realistic depiction of the actual ranges of these fossils.

No harm, no foul, I guess although past experience dictates that we simplify the stories fossils tell at our own peril. Creationists (and other science deniers) have a thing for rigid literalism.

For fun, I thought I would fire up the Paleobiology Database to have a look at what the actual distribution of these fossils might look like. Among an assortment of fun tools, PBDB allows you to plot fossil distributions on paleomaps to get a sense for how the ranges of fossil taxa maps on to former continental configurations.

So I punched in Glossopteris, Cynognathus, Lystrosaurus and Mesosaurus, set the map to show the approximate location of the continents at the Permo-Triassic boundary, and here is what I came up with:

Lots of overlapping colored dots. Obviously it needs some more beautification to really bring out the story. So I decided to follow the overall look of the “iconic” version and place polygons over each species’ range:

I left off Glossopteris since it would effectively cover all the land shown in the map. I’m also choosing to sweep under the rug the case of the Chinese Lystrosaurus and Glossopteris which would require a more detailed discussion than I can feasibly get into here. That or I am part of a global tectono-evolutionary old-earth conspiracy that uses free publicly accessible data to deceive the masses.

Er, anyway. You can see the problem here. Glossopteris, Mesosaurus, Lystrosaurus and Cynognathus all overlapped extensively in space (though they were not all contemporaries) and any figure that accurately illustrates their ranges looses the striking aspect of Colbert’s map with four fossils stitching the southern continents together.

But when I started this post today was tomorrow and  I am too lazy to go and fix that first paragraph. Time marches onward, the continents wheel about the planet, species evolve and ebb away. The great Glossopteris forests have evaporated, Rasmus Villumsen (dude on the right) lies buried under an estimated 100 meters of snow, Antarctic ice sheets peel backward revealing a long-lost Triassic menagerie. And I am going to bed.

*We share a birthday with Coco Crisp, Lyle Lovett and Bo Bice. True story.

Flippant

14 September 2011

Deep in some dream last night, I flip a rock and reveal an isopod the size of a silver dollar. Excited I snatch her up to show somebody, I cannot say who, but as I walk the crustacean ebbs to standard lilliputian proportions. Or maybe it’s my hands that are growing.

This all sounds pretty Jungian, or maybe worse, and I suppose soil is the great collective unconscious of terrestrial ecosystems (huh?)

But I guess I’m just a little haunted for not making more of International Rock-Flipping Day 2011.

I did get the chance to turn a few stones. As it happened, some of the same stones as when I first observed the holiday four years ago. Not surprisingly, more or less the same crowd turned up. Minus a weevil, plus a planarian.

Here I count representatives of no fewer than six independent invasions of land, not even counting the plants or fungi — nor the vertebrates which, apart from myself largely didn’t show. Hunkered beneath the twenty million-year-old fossilized shell of a bivalve, one clade that never made it out of the water in any respectable way. Sort of crazy.

Totally forgot the most important part:

Thomas Jefferson, the reluctant seismologist

24 August 2011

Photo by Trevor.Huxman used under Creative Commons 2.0

Depite his distinction as the first American paleontologist (sorta), Thomas Jefferson was something of geophobe.  In a letter written in 1805, Jefferson confessed:

I have not much indulged myself in geological inquiries, from a belief that the skin-deep scratches which we can make or find on the surface of the earth, do not repay our time with as certain and useful deductions as our pursuits in some other branches.

Five years later, fresh out of the Presidency, Jefferson ducked an inquiry from Thomas Cooper regarding the geology of Virginia on similar grounds, “Our researches into the texture of our globe could be but so superficial, compared with its vast interior construction, that I saw no safety of conclusion from the one, as to the other.”

Despite his avowed geo-agnosticism, Jefferson was both well-versed in the geological thinking of his day and an attentive observer of the geologic forces that shaped the landscape around him. In Notes on the State of Virginia Jefferson provides a detailed discussion of the Deluge theory that dominated geological thinking in the 18th Century, but voices considerable skepticism that the distribution of rocks and fossils on the Earth could be easily explained by events recorded in Genesis. Jefferson recognized that tilted strata and seashells lodged in the sides of mountains suggested some significant geological “convulsions” in the past. But he was never comfortable that studies of rocks could ever truly clarify the ancient history of the Earth, concluding, “Ignorance is preferable to error; and he is less remote from truth who believes nothing, than he who believes what is wrong.”

Nevertheless, later in that same work Jefferson wrote thoughtfully about the geomorphic landscape of western Virginia, in prose so vivid that it puts John McPhee to shame. Here he even reveals some nascent appreciation for the geologic forces that shaped that terrain.

The passage of the Patowmac through the Blue ridge is perhaps one of the most stupendous scenes in nature. You stand on a very high point of land. On your right comes up the Shenandoah, having ranged along the foot of the mountain an hundred miles to seek a vent. On your left approaches the Patowmac, in quest of a passage also. In the moment of their junction they rush together against the mountain, rend it asunder, and pass off to the sea. The first glance of this scene hurries our senses into the opinion, that this earth has been created in time, that the mountains were formed first, that the rivers began to flow afterwards, that in this place particularly they have been dammed up by the Blue ridge of mountains, and have formed an ocean which filled the whole valley; that continuing to rise they have at length broken over at this spot, and have torn the mountain down from its summit to its base. The piles of rock on each hand, but particularly on the Shenandoah, the evident marks of their disrupture and avulsion from their beds by the most powerful agents of nature, corroborate the impression. But the distant finishing which nature has given to the picture is of a very different character. It is a true contrast to the fore-ground. It is as placid and delightful, as that is wild and tremendous. For the mountain being cloven asunder, she presents to your eye, through the cleft, a small catch of smooth blue horizon, at an infinite distance in the plain country, inviting you, as it were, from the riot and tumult roaring around, to pass through the breach and participate of the calm below. Here the eye ultimately composes itself; and that way too the road happens actually to lead. You cross the Patowmac above the junction, pass along its side through the base of the mountain for three miles, its terrible precipices hanging in fragments over you, and within about 20 miles reach Frederictown and the fine country round that. This scene is worth a voyage across the Atlantic. Yet here, as in the neighbourhood of the natural bridge, are people who have passed their lives within half a dozen miles, and have never been to survey these monuments of a war between rivers and mountains, which must have shaken the earth itself to its center. – Thomas Jefferson, Notes on the State of Virginia 1781-1783.

But sometimes the mountain comes to Monticello. Jefferson himself recorded a convulsion that shook the state of Virginia in 1774,

“Feb. 21, at 2:11 P. M. felt a shock of an earthquake at Monticello. it shook the houses so sensibly everybody ran out of doors.” – Excerpt from Thomas Jefferson’s Garden Book, edited by Edwin Morris Betts (1999).

Despite this rather cool account, the 1774 quake may have played a role in a family calamity, the death of Jefferson’s sister Elizabeth, whose body was found floating in the Rivanna river three days after the quake. Elizabeth, “rather deficient in intellect” may have been attempting to flee from the earthquake and subsequent aftershocks when she was caught up in the flooding river. Maybe.

Geologic instability in central Virginia also shook up Jefferson’s granddaughter, when a quake hit in 1833.

Edgehill, Aug. 28, 1833.
… We had the most severe shock from an earthquake yesterday morning that had ever been experienced before by any of us … When it began the noise resembled the rolling of a wheel barrow, or something heavier, under the house, but gradually increasing until the house trembled all over. A dressing box on one of the tables being open, and the top leaning against the wall, was shaken almost off the table. It would have fallen, I suppose, if its fall had not been arrested by Mary Page’s hand, which she put out to save it. The windows rattled violently, and I began to fear the chimney might be shaken off, and made Emily, who was sitting near the fireplace … move away. When it had reached its heighth it gradually diminished until it went off entirely. The children from the nursery ran into my room, and Patsy and Mary followed them. I never saw so many pale faces and blue lips. I think it must have been partly occasioned by the motion: of the house and partly from terror … I have heard of the trembling of a vessel in a storm sometimes, & I think the motion of the house must have resembled it. – From MacCarthy 1958, “A Note on the Virginia Earthquake of 1833”.

Judging from contemporary accounts, that quake was likely centered on the same Central Virginia Seismic Zone that gave rise to yesterday’s tremor. The 1774 earthquake felt by Jefferson might well have had similar origins.

It’s hard not to wonder. Perhaps, if the magnitude of the 1774 Virginia earthquake that shook Monticello had been on par with the August 23, 2011 quake, it might have shaken into Jefferson a greater curiosity about the goings on beneath his feet. But, perhaps it’s for the best he didn’t get distracted, Jefferson had other things to do.

It is now above a fortnight since Congress should have met, and six States only appear. We have some hopes of Rhode Island coming in to-day, but when two more will be added seems as insuceptible of calculation as when the next earthquake will happen – Thomas Jefferson in a letter to James Madison, December 1783.

Postscript: 1000000 bonus points to the enterprising journalist or historian who tracks down Jefferson’s living descendants and records their personal experience of yesterday’s earthquake for posterity.

DOODZ! ALI∃NZ!!!1!

3 December 2010
Or maybe just a gravid female Mono Lake Brine Shrimp, Artemia monica.
heard if you go into the bathroom with a candle, turn the lights off, and whisper “reversed chirality” into the mirror seventy-three times you can actually *see* the shadow biosphere”

Well, I heard that arsenic makes you fat. And horny.

“Well, I heard that Tesla invented ununquadium-based life, you know, and hid it in a mountain in Colorado, and,”

I heard that Saturn’s moon Titan is made of liquid unicorns!”

Sorry.  The universe is a pretty crazy place, our own little stony clot of matter being no exception, and as things go, life is, really.

As I’m sure you have already heard, we are made of star stuff, and this connection is evident in how our own elemental makeup broadly mirrors that of the Earth and the Universe as a whole.  The six elements commonly regarded as the primary building blocks of life, hydrogen, oxygen, carbon, phosphorus, sulfur and nitrogen are the 1st, 3rd, 10th, 13th, 15th and 32nd most abundant elements in the Earth’s crust.  Other biologically important elements (e.g. iron, calcium, magnesium, sodium, potasium) largely round out the top 10 and the relative paucity of nitrogen in the crust is more than made up for by its superabundance in the atmosphere (thanks diazotrophs, we owe you one)

Stepping back a bit, CHNOPS and FeCaMgNaK all rank in the top 20 in elemental abundance in the universe.

To put things into perspective, arsenic, the subject of some breathless reportage today, is quite a bit rarer in the universe.  It ranks 41st in abundance in the universe, just behind tellurium (number 40) and just ahead of freaking yttrium (number 42).  The same goes for our own planet in particular where arsenic ranks at 48th in abundance by mass percentage.

(Incidentally, I got thes figures from WolframAlpha the first time that I’ve actually been able to put that seemingly powerful tool to any sort of meaningful use.)

Not to rain on anyone’s arsenic alien parade but if Earth’s boring old vanilla non-shadow biosphere (the overwhelming bulk of it anyway) is any indication, if life exists elsewhere in the universe it seems pretty likely that its elemental composition will more or less reflect the overall composition of the universe. Pinning hopes on a relatively scare substance, arsenic, when the alternative, phosphorous is rather abundant seems misguided. Just sayin’

 


These new experiments
show some bacteria already adapted to a fairly chemically extreme environment might, maybe, incorporate arsenic into their biomolecules when subjected to fairly elaborate artificial laboratory conditions.  But making the leap that this tells us something about what life outside (or hidden deep inside) our planet might be like, is equivalent to saying that because humans can survive and thrive with artificial hips that we should expect to find martian metazoans with composite titanium and plastic skeletons.

None of which is to say that this new discovery is anything short of totally rad. It also shows the value of doggedly pursuing what might seem like wacky ideas. That the prediction of parallel properties of arsenic and phosphorus might have biological significance is the stuff of science fiction, so it’s pretty easy to see why the press has gotten a little, uh, carried away by all of this. Also, dude, the periodic table came to Mendeleev in a dream!

Somewhat lost in all of the coverage about this remarkable Mono monad is the fact that Mono Lake sports an entire ecosystem that is very bizarre, if decidedly terrestrial. But you don’t have to take my word for it:

There are no fish in Mono Lake—no frogs, no snakes, no pollywogs—nothing, in fact, that goes to make life desirable. Millions of wild ducks and sea-gulls swim about the surface, but no living thing exists under the surface, except a white feathery sort of worm, one half an inch long, which looks like a bit of white thread frayed out at the sides. If you dip up a gallon of water, you will get about fifteen thousand of these. They give to the water a sort of grayish-white appearance. Then there is a fly, which looks something like our house fly. These settle on the beach to eat the worms that wash ashore—and any time, you can see there a belt of flies an inch deep and six feet wide, and this belt extends clear around the lake—a belt of flies one hundred miles long. If you throw a stone among them, they swarm up so thick that they look dense, like a cloud. You can hold them under water as long as you please—they do not mind it—they are only proud of it. When you let them go, they pop up to the surface as dry as a patent office report, and walk off as unconcernedly as if they had been educated especially with a view to affording instructive entertainment to man in that particular way. Providence leaves nothing to go by chance. All things have their uses and their part and proper place in Nature’s economy: the ducks eat the flies—the flies eat the worms—the Indians eat all three—the wild cats eat the Indians—the white folks eat the wild cats—and thus all things are lovely. – Mark Twain, Roughing It 1872.

Be sure to click through for more mildly racist humor (lighten up, dude, it’s satire!)  Somehow, Twain overlooked that other strange component of the Mono 80s hair-rockers.

The usual suspects have great, sober, and thought-provoking coverage of the new discovery.

Anyway though, if you really want to know about extraterrestrials, there’s only one person to ask:

McFarthest Spot and Smoke Creek Sam’s last stand

20 October 2010

Shows what I know.  What I thought might be a challenging “Where on Google Earth” was correctly pinned down in less than 12 hours. Winner Lockwood has already posted #218 on Outside the Interzone and it has stumped me, at least.

My not so mysterious mystery photo shows lower Guano Valley, straddling the border of Lake County, Oregon and Washoe County, Nevada.  As Lockwood correctly noted, Doherty Slide, descending from Guano Rim is visible in the upper right.  The rim and the valley take their name apparently from the distasteful water found in the playa lakes that dot the valley floor, remnants of a pluvial lake that once filled the graben valley.

Doherty Slide is named for some Irish dude and the manner of descent adopted by wagons of yore wherein the wheels were locked and the wagons slid down the rocky slope.  Today Oregon 140 follows the same route, and by all accounts remains a harrowing trip.  I haven’t done it yet.  Looking forward to it though.

I don’t have much to add on the geology, already quite adequately summarized by Lockwood and typical for the region: Plio-Pleistocene volcanics and lake deposits modified by extensional faulting.  It’s worth noting, for those to whom such things are noteworthy, that the USGS geochemical standard for andesite, USGS AGV-1 (since replaced by USGS AGV-2 from the same locality), was collected on or around Doherty Slide.

I also want to call your attention to some other features visible in this otherwise desolate and unpopulated corner of the Great Basin:

  • The current location of McFarthest Spot, the furthest one can possibly get from a McDonald’s in the CONUS (+DC), is just below center.
  • A briefly held early hang gliding record was set by Chris Price in 1974 from Guano Rim, which remains a popular launch location.  At 13.5 miles the flight was an order of  magnitude shorter than the current record, but given the state of the sport at that time seems pretty impressive:
  • Smoke Creek Sam’s Last Stand, a decisive battle in the Snake War fought between the 2nd California Cavalry division of the United States Cavalry and an alliance of Paiute, Shoshone and Bannocks took place on the alluvial fan right of center.

From Michno 2007 The Deadliest Indian War in the West

here is an account of the battle from Fairfield’s Pioneer History of Lassen County 1916

  • Not easily illustrated in the photo, and perhaps not in view at all, obsidian sourced from Guano Valley has been found some 500 miles away in the California Channel Islands, which blows my mind.

If all of this seems to you the making of some awesome historical fiction centered on a few square miles but spanning some 5 million years.  Well I’m right ahead of you there. Just kidding, I’m super busy scienceing dude.

Where on Google Earth #217

18 October 2010

Let’s dust off the old keisaku and slap this sleepy blog back into being shall we?

I had the good fortune to properly triangulate the identity of the last “Where on Google Earth” challenge over on Glacial Till and so am duty bound to post the next challenge shown above.  You know the drill: give the coordinates and some explanation in the comments below.  The correct answer earns the honor of posting the next challenge on their blog.

Happy hunting!

Holding Pattern

9 August 2010

“Windwave” Michael Oppenheimer

Always with the pelicans.  Remember when it was the atmospheric scientists that were the vanguard of neo-atheism?