Geology

When I was given a grab-bag of rock specimens the other week, this piece of limestone studded with little Devonian corals caught my eye. A few quick tests told me I could try acid digestion on it, so that's what I did. See the process, the results and the trade-offs after I bathed it in hydrochloric acid.

Related:
The acid test
Oxalic acid treatment of minerals
Fossil collecting tools
Non-fossils
_{Thamnopora coral specimen — Geology Guide photo}

I spent a fair amount of my late teens visiting wild caves. Then I moved to a place with no caves, moved again, and many years later I'm not sure I could repeat anything I used to do underground. But I still enjoy a tour of a good show cave, especially when they lay on the science instead of the "this formation looks like Snoopy" stuff. And I can still put up a mean quiz on caves. Don't let the questions drive you BATS.

For me, the science news of the week was the Nature paper this week announcing that the genes of Emiliania huxleyi have been sequenced. "Ehux" is an extremely important member of the ocean's plankton that grows almost everywhere in the world and pulls carbon dioxide out of the water—and thus, indirectly, the atmosphere—to make those beautiful microscopic disks of calcite, called coccoliths, with which it clothes itself. That makes Ehux the foremost coccolithophore, a word every kid should know. Coccoliths accumulate into the rock known as chalk. The Cretaceous Period got its name from the Latin word for chalk. That means that the age usually known for its dinosaurs (and sometimes its ammonoids) is really the Age of Coccolithophores.

Anyway, Ehux is an important target for gene sequencing. The Nature paper, which notably is open-access, shows that this organism is unusually diverse and has a huge genome with a large number of "optional" genes. This kind of "pan genome" has not previously been found outside the bacteria. I urge you to puzzle your way through the paper as well as read some of the news stories about it.
_{Emiliania huxleyi — Gerhard Langer, Alfred Wegener Institute}

Simon Wellings, of the Metageologist blog, has finally addressed a key topic for the future of the geoscientific professions: are we properly fascinating our children with geology? Since kids avoid the outdoors these days and get their stimulation from video screens, his new post on the geology of children's entertainment is timely. Do the artists who keep our kids' attention care about rocks and landforms?

Wellings' touchstone is Leonardo da Vinci, who is considered by historians of science to be the first close observer of landscape. Leonardo did a good job on his rocks; the makers of The Octonauts—well, "if there is a geological advisor," Wellings says, "then they should be shot." But Pixar acquits itself well. Realistic landscapes and rocks are a strong test of an artist's skill. I've always thought that the manufacturers of those fake boulders you hide your house keys in could do a much better job.

Related:
Seeing Disney's "Dinosaur"
Quicksand in the movies and reality
"Volcano" and "Dante's Peak"
Geology and the movies
An artist's version of Plymouth Rock
Octonauts toys reviewed

I love it when Forum visitors come by with pictures of things they've found. It's refreshing when ordinary, non-geological people respond to objects as they really are. This piece of waste from some historical glassmaker is a great example. The geologist ignores it because it's so obviously not a real rock. The ordinary person loves it because it's so obviously beautiful. Only the industrial archaeologist can tell us what it really is, whatever "really" means. All I know is that industrial waste of all kinds follows humans around, even in places you might think are pristine like the long-reforested environs of Muncy, Pennsylvania, where this was found. It's a pleasure to add it to the gallery of artificial rocks.
_{Photo by Forum member cchopper1}

I am spending much of this weekend traveling. The best part of traveling is getting a primo window seat, with clean glass, and watching the landscape crawl by below. If I could imagine something even better, it would be riding the International Space Station. I might not be as entertaining as astronaut Chris Hadfield (who really ought to have his own web domain by now), but I surely would be sharing as many photos as he did during his stint upstairs. The most valuable thing the space program has brought us, I believe, is not the possibility of expanding into the universe but the synoptic view of Earth it has given us.

Speaking of which:
San Andreas fault from an airliner
Colorado cuestas from an airliner
Aerial stereopair of the Uinta Mountains
Earth images from space

Geology gave the world the gift of time: not just the measly millennia counted by old civilizations, but millions of years and billions of years, more years than anyone could count. It made even the absurdly long sacred chronologies of the Hindus look reasonable. And as we explored all that time, we figured out how to organize it into structures of time, hierarchies of time periods with, eventually, actual dates assigned to them. That's what this week's "Who Wants to Be a Geo-Whiz?" quiz is about: geologic time. Now don't dawdle, you've only got a week.

Celadonite is a mica mineral, but it never forms the typical flexible flakes of muscovite. Nevertheless, mineralogists consider the two mineral species to be end members of a series with muscovite at the aluminum end and celadonite at the iron end (and phengite in between).

That may make sense to a crystallographer, but in geologic reality the two have very different habitats. Muscovite is an abundant primary mineral in granites and a rock-forming mineral in metasedimentary rocks. Celadonite is a rare secondary mineral found as amygdules, filling the vesicles of basalt flows.

Both, as it happens, are useful to painters and artisans. Powdered muscovite adds sheen and glitter to paints and plastics, while celadonite is prized as a blue-green pigment.
_{Celadonite — Geology Guide photo}

Last week's gift of a bag of specimens included a chip of schist sprinkled with little red-purple prisms: piemontite. It's the manganese-bearing member of the epidote family, and I'm pleased to have a typical specimen to show you rather than some big rock-star crystal that doesn't resemble what you'd find in the field. See it close up in the silicate minerals gallery.
_{Piemontite — Geology Guide photo}

A certain fraction of New Age-y types love to tell us that the ancients, thousands of years ago, mastered technologies like levitation and psychic healing that we can't imagine today. The grain of truth in those beliefs is the case of ancient Roman concrete. The engineers of the Roman empire built concrete structures that still function today, whereas little if any of our modern concrete could endure for twenty centuries.

Industrial geochemists have recently run samples from a concrete breakwater in Pozzuoli Bay near Naples and learned in nanometer-level detail why the Roman ways worked so well. It was the combination of the pozzolan volcanic ash and seawater that created a subtly different product. It made great concrete without needing the high-temperature process we use today to make portland cement. This finding offers the promise of producing concrete in regions with lots of volcanic ash and saving energy in this greenhouse-intensive industrial process.

Details:
UC Berkeley news release
Lawrence Berkeley Lab news release
About cement and concrete
Gallery of artificial rocks