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20 January 2021

Peering through

When hiking recently in my neighborhood, I saw this gleaming apparition appear in an eroded gully in a dirt road:

Mylonite exposed in a gully. Lens cap for scale.

Those multicolored stripes are varying compositions in a zone of ultramylonite: ductilely-sheared-out rock that formed in the deep equivalent of a “fault” in the Blue Ridge basement complex. We call it a “shear zone” most of the time, but a better descriptor would be “high strain zone.” These rocks are STRAINED, sheared out from original crystals with shapes akin to dice, transformed into platy flakey smears as thin as crêpe paper. The protolith rocks here are Mesoproterozoic in age, granitoids related to the Grenville Orogeny and the formation of Rodinia, but the shearing is younger, related to Appalachian mountain-building (making Pangaea) during the Paleozoic.

Surrounded by dirt and deciduous leaves, this is a palimpsest view into the Wilson Cycle.

There were not a ton of outcrops on this hike. A few isolated boulders perhaps, but mostly it was trees and trees, and trees. Catching a glimpse of such epic rocks almost completely obscured beneath dirt and leaves was a beautiful moment for me, akin to shafts of sunlight piercing the space between leaden clouds on a dismal day. You can imagine the heavenly choir of angelic voices singing in my mind…

If you will forgive me a moment of sentimental analogizing, I’m reminded of the national moment at hand. Today is the transition out of an era of hatred, fear, nonsense, and death, into an era that will hopefully be guided by empiricism, empathy, and an economics of equality.

This past year has been hellish: not only has a deadly pandemic been nurtured through neglect by the nation’s elected leaders, but the soon-to-be-ex-president has given a full-throated endorsement of racism and racists, and trained his followers in the fine art of ignoring facts. (Rereading Orwell’s 1984 four years ago turned out to be quite a good call.) On top of those national ills, my family and I moved to a new town and new jobs and new everything, pretty much at the precise moment when it was near-impossible to make new friends and nurture new relationships with colleagues, students, neighbors, and such. Though we get outside plenty, the social isolation feels a lot like cabin fever.

It’s been really hard for me to focus on work this year, on creativity, on much of anything scholarly, as the world around me burns and is debased and injects my dreams with anxiety.

I write now, in early 2021, after a year of near stasis on this blog, optimistic that things are getting better, and that I’ll soon be able to write more. I regret my lack of productivity here over the past year, but there have been more vital things that needed my attention, from moving four tons of rocks to my new lab to repairing my new house to facilitating emergency room visits for my son. Thankfully, being infected with COVID-19 hasn’t been one of them. But I have to tell you: the past year has been HARD. It’s been really hard. I’m not sad to shut the door on the Trumpocene. It’s been a tumultuous year without much joy.

But there’s something about deformed rocks that gets my pulse beating. The hike may have been mostly dirt and gray vegetation, but here was a glimpse of something beautiful, something meaningful, only just revealed. The past year may have been bleak, but I have high hopes that tomorrow is wonderful, and beautiful, and leads to the satisfaction of understanding, of perspective on the big picture.

Here’s to more ultramylonite in the coming years, and less dirt.

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18 January 2021

Book report

First Light: Switching on Stars at the Dawn of Time, by Emma Chapman

Emma Chapman is keen on understanding the first stars. The first stars are different from modern stars, in their composition as well as their size. Specifically, Chapman notes that the earliest stars (unchronologically named Population III in contrast to modern Population I) were huge (20 solar masses) and “burned” (fused) hydrogen for 10 million years, followed by helium for 1 million , and then beryllium → carbon (300 years), oxygen (200 days), and silicon (2 days), for proportionately less and less time in the years remaining to them. Their life cycles went by quickly. Chapman is apparently typical of astronomers in taking anything of higher atomic weight than helium as a “metal,” presenting the astronomer’s periodic table as one of the earliest figures in the book: hydrogen/helium/METALSMETALS METALS What distinguishes the first stars (Population III) from the rest is they had none of these “metals” at their start, just hydrogen. So the search for Population III is really the search for “low metallicity” stars. An extended analogy is offered in one chapter between cyanobacteria polluting their surroundings with oxygen, and Population III stars polluting the interstellar medium with metals. Just as stromatolites changed the ambient geochemical conditions on Earth forever, so too did Population III stars forever alter the cosmic trajectory by contaminating it with metals of their own generation. Archaeology gets invoked as an analogy too – how can an Egyptologist figure out what’s pristine about a newly discovered tomb, what’s been extracted by grave robbers, and what’s been introduced as more recent contributions? A similar task faces astronomers as they consider the various aspects of electromagnetic radiation they gather from the cosmos. The final chapter looks ahead to future missions / experiments, describing their intended design and what data they seek. All told, I found this to be an excellent book: it’s more detailed than something general, the sort of thing Neil Degrasse Tyson might write. Chapman writes about the search that motivates her whole career, and she writes with a zippy, cheeky passion that’s infectious.

Soonish, by Kelly and Zach Weinersmith

I’m delighted that in moving to Albemarle County, I’ve got the Weinersmiths as neighbors. Their daughter is not too much younger than my son, and both families have taken a similar approach to the COVID-19 pandemic, leading us into isolation, but that’s bad for the kids, so we get together weekly for well-ventilated hikes at the land around one or another’s house. Zach writes the popular webcomic Saturday Morning Breakfast Cereal, and Kelly is a parasitologist. They both describe themselves as nerds. This book, their first joint collaboration, is an exploration of ten emerging technologies. They look at cheap space travel, mining asteroids, programmable matter, augmented reality, synthetic biology, and personalized medicine. The value of this book is that the two authors are extremely fastidious about tracking down true source material, and striving very much to not be wrong. But that scholarly dedication doesn’t imply a staid or stuffy book. Far from it, the text is laden with goofy jokes and evocative analogies, and every few pages is one of Zach’s cartoons. The humor is like the compressed air beneath a hovercraft – it lofts the whole narrative up, and carries it along through a tremendous review of the relevant literature. The Weinersmiths have made great use of footnotes, too – each contains a pithy clarification, an odd tangent, or an amusing joke. Super enjoyable, and super informative.

Consider Phlebas, by Iain M. Banks

Many moons ago in the middle of the pandemic, I asked for recommendations about books to read, and this science fiction novel was recommended on the basis of the fact that one of its scenes took place “in a batholith.” That’s all I knew about it going in, but I was able to get a paperback copy for a few bucks, so why not? It turns out this is the first novel in a series of books, all set in the future of what appears to be our galaxy. This one details a minor plot point in a larger war between two societies. The arc of the story follows the efforts of an agent on one side of this conflict in his attempts to locate and capture a self-contained artificial intelligence capsule developed by the other side. (It is this AI, called a “Mind,” that has hidden itself in a tunnel system that was bored into the cited batholith.) It turns out to be quite a series of adventures for the agent to get to the Mind and extract it. It’s a high adrenaline book with a lot of violent and spectacular occurrences, and pluck and luck on the part of the protagonist. Many of Banks’ details are familiar (trains, for instance), but others are imaginative and original (the idea of ring-shaped planet-equivalents called orbitals). It manages to feel distinctly alien while also resonating as relevant to a human at the same time. I wasn’t thrilled with the ending, but the reading of the novel was enjoyable and escapist.

The Young Earth: An introduction to Archaean geology, by E.G. Nesbit

This is an accounting of Archean geology by one of its practitioners. It covers igneous, sedimentary, and metamorphic processes relating to the Archean, with particular attention given to TTG suites, komatiites, stromatolites, distinctive characteristics of Archean sediments, iron formations, and the fossils of ancient microbial life. It was surprisingly readable for an academic work. It felt a bit dated (it was published in 1987), but it felt authentic and informed too. I am glad to have read it – it definitely expanded my horizons beyond the Canadian and South African outcrops I know to emphasize Australia, Greenland, and Mozambique — but I would be even more glad for a 2021 2nd edition!!

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15 January 2021

Friday fold: Three from Alaska

Earlier this week, I was alerted to an online photo collection from the Alaska Division of Geological and Geophysical Surveys. For those of us who are feeling the lack of field work over the past year, it’s pleasant to browse through them and get a taste of backcountry Alaska. Many of the photos are shot on old slide film, but that kind of adds to the “Alaskaness” of them in my view.

Here are a couple of fold photos from the collection, both by Melanie Werdon, both from 2016 near Tok:

Crenulated foliation in schist or phyllite

And one from 1977 by Charles G. (Gil) Mull:

Happy Friday to you.

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1 January 2021

2020 Yard List(s!)

It’s my little new year’s tradition to present here my tally of bird species seen in my yard over the course of the year just concluded.

Here are the previous iterations:

Things are different this year, not because of the pandemic, but because I moved over the summer. So this year I have two lists: a final one for the Fort Valley property, and a new one for our new home, an Albemarle County property near Buck Mountain. Each represents about half a year of time. As usual, I present them in chronological order of first sighting, so there’s a rough seasonality you can tease out of them. Because there is substantial overlap, I’ve bolded the birds that are unique to each list. This perhaps allows a bit of distinction to be made between the two places in terms of the habitat available. There’s more open space and more water at the new place, for instance.

The last Fort Valley yard list:

  1. Raven
  2. American crow
  3. Blue jay
  4. Turkey vulture
  5. Mourning dove
  6. Dark-eyed junco
  7. Red-shouldered hawk
  8. Downy woodpecker
  9. Red-bellied woodpecker
  10. White-breasted nuthatch
  11. Chickadee
    (I never was able to figure out if these were Carolina or Black-capped chickadees.)
  12. Tufted titmouse
  13. Brown creeper
  14. Golden-crowned kinglet
  15. American goldfinch
  16. Red-tailed hawk
  17. Yellow-bellied sapsucker
  18. Pileated woodpecker
  19. Northern flicker
  20. Eastern phoebe
  21. Wild turkey
  22. Screech owl
  23. Pine warbler
  24. Canada geese
  25. Winter wren
  26. Eastern bluebird
  27. Chipping sparrow
  28. Brown-headed cowbird
  29. American robin
  30. Ruby-crowned kinglet
  31. Whippoorwill
  32. Blue-gray gnatcatcher
  33. Brown thrasher
  34. Blue-headed vireo
  35. Ovenbird
  36. Ruby-throated hummingbird
  37. Black vulture
  38. Hermit thrush
  39. Yellow-rumped warbler
  40. Wood thrush
  41. Great crested flycatcher
  42. Blackburnian warbler
  43. Black-throated green warbler
  44. Red-eyed vireo
  45. Scarlet tanager
  46. Indigo bunting
  47. Great blue heron
  48. Cedar waxwings
  49. Eastern wood-pewee
  50. Osprey
  51. American kestrel
    (This was a first for that yard; usually these are open-country birds, not forest dwellers.)
  52. Great horned owl
  53. Sharp-shinned hawk

The first Buck Mountain yard list:

  1. Ruby-throated hummingbird
  2. Blue jay
  3. Yellow-billed cuckoo
  4. Northern cardinal
  5. Turkey vulture
  6. Raven
  7. American robin
  8. Chimney swift
  9. Red-tailed hawk
  10. Black vulture
  11. Chipping sparrow
  12. Broad-winged hawk
  13. Great blue heron
  14. Sharp-shinned hawk
  15. Eastern bluebird
  16. Mourning dove
  17. Carolina chickadee
    (…Now that it’s for sure which one’s range I’m in!)
  18. Green heron
  19. Eastern towhee
  20. Eastern phoebe
  21. Carolina wren
  22. Red-shouldered hawk
  23. Blue-gray gnatcatcher
  24. White-breasted nuthatch
  25. Northern mockingbird
  26. Red-eyed vireo
  27. Tufted titmouse
  28. Brown thrasher
  29. Screech owl
  30. Downy woodpecker
  31. Prairie warbler
  32. Pine warbler
  33. Belted kingfisher
  34. Barred owl
  35. Canada geese
  36. Cedar waxwings
  37. (unidentified ducks flying overhead)
  38. Yellow-bellied sapsucker
  39. American goldfinch
  40. Dark-eyed junco
  41. White-throated sparrow
  42. American crow
  43. Pine siskin
  44. Yellow-rumped warbler
  45. Northern flicker
  46. Ruby-crowned kinglet
  47. Red-bellied woodpecker
  48. Brown creeper
  49. Song sparrow
  50. Hairy woodpecker
  51. Red-breasted nuthatch
  52. Bald eagle
  53. Winter wren

Interesting that it worked out to 53 apiece. The grand total is 58. Here’s to better birding in 2021! Happy new year!

 

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13 November 2020

Friday fold: stairsteps in the Tonoloway

This Friday fold is a bed of Tonoloway Formation dolostone, from a pile of scree below a roadcut in Grant County, West Virginia, on Corridor H. It’s got two lovely “stairstep” style folds superimposed on it.

I love folds that are expressed in three dimensions. Very satisfying.

Happy Friday.

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9 October 2020

Friday fold: Torcross

Looks like we’re sticking with the U.K. for Friday folds, for the time being…

This lovely beast comes to us from Torcross, via Danny Stubbs, who shared it on Twitter this past week.

That’s from the Meadfoot Group of slates, cross-cut by quartz veins.

In this follow-up image, Danny shares that sometimes the quartz veins have enjoyed some folding too:

Happy Friday to all.

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2 October 2020

Friday fold: Northumberland

For the Friday fold this week, we travel to Northumberland, U.K. for this beautiful fold pair:

Robert McKibbin posted this image on Twitter this week, and graciously allowed me to feature it here.

Thank you Robert!

Happy Friday to all.

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18 September 2020

Friday fan: Death Valley, California

Working up some new images for my free, online Historical Geology textbook, I annotated a photograph I took in March of this alluvial fan in southern Death Valley. The development of desert varnish on older parts of the fan shows their age visually in a quick and easy way of determining fan deposit sequence:

I’ve been making a lot of these animated annotations as a way of conserving space in the “real estate” of the online text’s pages.

Happy Friday. Back to folds next week!

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11 September 2020

Friday fold: Boscastle, Cornwall

These images come from Lilly Wilson, an undergraduate geology student at the University of Bristol:

Here’s her original tweet, which has 4 images:

For my American readers, the Variscan is the European equivalent of the Alleghanian Orogeny in the Appalachian mountain belt. At the same time these rocks were being deformed, similar strata were experiencing similar folding in my backyard.

Lilly should also be commended for her choice of field assistant, who appears to be a shrewd judge of structural geological character:

Great rocks, excellent photos, and a thoughtful pooch, too – excellent tweeting! Thanks for sharing, Lilly.

Happy Friday all!

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4 September 2020

Friday fold: Home décor

Busy weeks lately; apologies for the minimal bloggery, friends.

For this week’s Friday fold, I offer you a view of some of the outdoor decorations at our new house:

In the lower basket there is a cut and polished block of Castile Formation rock gypsum + limestone, showing varves that have been folded, apparently by hydration/dehydration volume changes of the gypsum/anyhdrite laminae:

This is from the State Line outcrop on the border of Texas and New Mexico in the legendary Permian Basin. I collected it during the epic “Border to Beltway” field trip that Joshua Villalobos of El Paso Community College and I co-led something like seven years ago…

Happy Friday to you. I’m headed into the field today to track down some mylonite. Be well.

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