6 February 2016
I have a great book to recommend today – a book that takes a “Great Books” approach to tracking the advance of western science through history. The book is called, straightforwardly, The Story of Western Science. Its author is Susan Wise Bauer, who writes with a confident erudition and a clear, solid style. She surveys key works in the literature that illustrate the development of scientific thought – all of which are chosen not because they were necessarily the “firsts” in the field, i.e. the sorts of things a scientist would cite in a formal academic paper, but instead in many cases, key distillations of big ideas in the advance of science. Newton’s Principia merits attention, but so does Walter Alvarez’s T. Rex and the Crater of Doom.
It is exactly the right size of a book, and each work is evaluated in terms of its historical, social, and scientific context, and she writes about them elegantly, clearly in possession of an understanding solid enough that she can present the arguments, the insights, and the conundrums in clear, straightforward language.
The author has set up a companion website for the book, where excerpts from the great books are posted. This is a resource worth bookmarking – there’s great stuff here for an Honors-flavored historical geology course, of a capstone course for majors. (A quarter of the book is dedicated to geology.) Each chapter ends with a discussion about where to find the source material, the works being discussed.
Never have I experienced so comprehensive a survey written with such an economy of words. It’s an excellent distillation of the development of ideas, firmly pinned to a timeline of history, and flavored with relevant historical / societal context. Highly recommended.
5 February 2016
Happy Friday! Here’s another fold from Catalina Island, California – an antiform in metasediments, courtesy of Sarah Penniston-Dorland of the University of Maryland:
4 February 2016
While I’ve spent quality time in Ireland on previous trips, I’ve never been to Scotland. To me, it is terra incognita, and I am eager to explore it this summer. It was with delight then, that I delved into David Oldroyd’s The Highlands Controversy, which at once tickled many parts of my brain: the structural geology part, the history of geology part, and the part that gets giddy with anticipation of my upcoming travels in Europe.
The Northwest Highlands of Scotland are a neat place – one of the most remote and least populated portions of the British Isles, a site of classic structural geology (the Moine Thrust), and a new geopark. A great resource you may be interested in is this website from Rob Butler at the University of Leeds, UK, which explores the geology of the region in great detail.
In a nutshell, though, this is a place where thrust faults (low angle reverse faults, where the fault plane is almost identical in orientation to the bedding plane) were first used as a viable mechanism for explaining the geology. Rocks of various types along these faults were smeared out to make mylonites, and this was the spot where that lovely term was first applied.
This history explores the development of geologic thinking through about a hundred years of field work in the Northwest Highlands, starting with Roderick Murchison, king of the Silurian and his disciple Archibald Geike. Geike did a legendary hike traversing some of this geology, and here’s a great notion – recreating that hike in the modern day. Because I’ll have my three year old son in tow this summer, I doubt that’s in my future, but it’s a tantalizing notion. Oldroyd reveals Murchison as being obsessed with expanding the domain of the Silurian (you’ll recall he had a falling out with Adam Sedgewick on this topic, vs. the Cambrian). Hence, Murchison saw everything in the northwest highlands as Silurian in age. Because the rocks were either metamorphic or sparsely-fossiliferous sedimentary strata, he had little data to countermand his bias. Though he wasn’t able to explain how highly metamorphosed schist lay atop unmetamorphosed sandstones and limestones, Murchison wasn’t bothered. Superposition reigned supreme, so Murchison reasoned that some of these layers must simply be more susceptible to metamorphism than others. Geike towed the party line, and benefited greatly from Murchison’s patronage, eventually rising to direct the British Geological Survey.
Antagonizing Murchison, but eventually swept under the rug by Geike, was James Nicol, who advocated a role for faulting, but not thrust faulting – that wasn’t conceptually an option that was available to him at the time. Nicol’s faults were steeper, and feature prominently in the cross-sections he drew as interpretations of his field work. Many people caricature the Highlands Controversy as “Nicol got it right, but Murchison was more powerful, and eventually Peach and Horne vindicated Nicol.” But the reality Oldroyd reveals is more complicated than that: a story with multiple strands, and no single moment of scientific revelation. Nicol’s conclusions were flawed like Murchison’s, just in a different way.
Then along came Charles Lapworth. Not only did Lapworth steal away part of the Silurian and part of the Cambrian to make the Ordovician (through the clever use of graptolites as index fossils, a groundbreaking technique in its detail), but he also suggested that the Northwest Highlands were far more interesting than mere layer-cake geology with anomalously metamorphosed layers. He suggested serious deformation as the cause. Detailed mapping of the terrain disproved suppositions that stemmed from Murchison’s model, and Lapworth benefitted from reading about other examples of what today we would call fold and thrust belts, in the Alps (the work of Arnold Escher von der Linth and his protégée Albert Heim) and the Appalachians (the work of William Barton Rogers and his brother Henry Darwin Rogers). Lapworth didn’t solve the structure of the Northwest Highlands, but his work was more right than wrong, and critically served as catalyst to make the Geikefied Survey decide that they needed to take another look.
The detailed mapping was key to unraveling the enigma, and eventually John Horne and Benjamin Peach engaged in a concerted campaign of mapping on behalf of the survey that “solved” the problem once and for all. Thrust faulting was an ingredient they mixed into their recipe to great effect. This was when the Moine Thrust and its structurally lower counterparts were first decisively delineated.
Oldroyd’s treatment of the history of this particular issue is very well done, and methodical enough that I don’t feel I missed anything. At any rate, I could follow the arguments and the divergences in thinking, the social factors, etc. through time. His exposition is thorough, and readable. One thing he points out that I was astonished by is how shoddy the graphical images were that the earliest geologists to work in the area produced and published. The first map wasn’t published until thirty years into the controversy (Bonney, 1880), and it’s a sorry thing – no scale, no “north” arrow, no indication of topography, and no precise location of the site being mapped. Everything hitherto had been conceptual cross-sections, essentially the sorts of cartoons I like to draw, unconstrained by too many empirical facts.
In summary, The Highlands Controversy is worth your time to read if (a) you are a structural geologist, (b) you are interested in the history of science, or (c) if you plan to travel to northwest Scotland and want a solid background of the local geology soaked in the context of how that understanding developed.
29 January 2016
My friend Sarah Penniston-Dorland, of the University of Maryland, supplied this week’s Friday fold. it comes from Catalina Island, California, where Sarah just wrapped up some field work with two of her students. All three of them have given me permission to post the images here:
The Catalina Schist is a suite of subduction-related metamorphic rocks. These rocks are amphibolite facies gneisses, but part of the Catalina Schist. The metamorphic ages of the high grade rocks are ~115 Ma. There are a lot of migmatitic rocks in the amphibolite facies of the Catalina Schist.
I think there is a refolded fold in the main part of the main face of this scene:
Pretty cool. Sarah also documented some other folds on Catalina Island, and I hope to share some of those in the weeks to come.
27 January 2016
I’ve been doing some reading lately to get some foundational ideas established in my mind for my upcoming summer trip to Europe. This trip has three goals: (1) to gather key digital imagery (GigaPans, 360° photospheres, video) for curriculum to teach geoscience concepts and give students everywhere with particularly instructive geology in Iceland, Ireland, the UK, France, and Spain, (2) to scout out locations and logistics for a Summer 2017 NOVA field course in the UK and Ireland, and (3) to have a good time with my family, who will be coming with me.
One of the locations I’ve been keen to visit since forever is the village of Lyme Regis, on the coast of Dorset, in England. It was there that Mary Anning discovered the first icthyosaurs and plesiosaurs, and there are ammonites galore, as well. I think it would be great fun to hunt for fossils along those same beaches. So, to get into the mood, I recently listened to the audiobook version of Tracy Cevalier’s Remarkable Creatures, which tells Anning’s story in a fictionalized way that seems to be fairly solidly grounded in reality. The structure of the novel is based on Anning’s relationship with Elizabeth Philpot, a London transplant to Lyme and an avid fossilist as well. The two women trade off the role of narration in subsequent chapters, and tell their own personal stories as well as the larger scientific and societal tale of the discovery of species which had no counterpart in the modern world. Anning was “working class” and Philpot was derived from high society, and so their class differences are an important aspect of the tale. Henry de la Beche and Charles Lyell have cameos, and Cuvier’s shadow looms over their finds as arbiter of what’s anatomically legitimate, but William Buckland plays a big role, and William Conybeare serves as a bit of an antagonist.
It’s an excellent yarn, and I feel like I have more of an intuitive grasp of the setting and the sequence of events during Anning’s early life as a result of reading it. I enjoyed Remarkable Creatures, and recommend it to you.
20 January 2016
Here are some new “virtual samples” for you to check out:
Dessication cracks in Tonoloway Formation (Silurian):
Link Image by Callan Bentley
Random conglomerate (unknown age and formation):
Link Image by Robin Rohrback
Skolithos trace fossils (tops) in Hampshire Formation (Devonian):
Link Image by Callan Bentley
Crinoid calyx fossil (unknown age and formation):
Link Image by Callan Bentley
Iron oxide staining in Tuscarora Formation quartzite (Silurian):
Link Image by Callan Bentley
Quartz pebble meta-conglomerate in Tuscarora Formation quartzite (Silurian):
Link Image by Callan Bentley
15 January 2016
The geology east of Harpers Ferry, West Virginia, is cool. It’s Blue Ridge rocks, from basement to the cover sequence, tilted to the west and broken and repeated by the Short Hill Fault. Here’s a look at a detail of the Geology of the Harpers Ferry quadrangle by Southworth and Brezinski (1996).
So there’s a fault! Good – but the title of this post isn’t “Friday fault” – Where’s the fold?
Let’s zoom in to this region:
There, my friend Katarina Doctor supplied this aerial photo of a fold in Weverton quartzite that crops out in the middle of the Potomac River (when water levels are low, anyhow):
Differential weathering of the quartz-rich Weverton Formation here has etched out the Blue Ridge and Short Hill into a closely-spaced duo of ridges, separated by a valley underlain by less resistant rocks (basement granitoids, mainly). But the Potomac River was superposed on these structures prior to the recent differential weathering, and it cuts across them at almost a right angle, producing a distinctive double water gap, as seen in this LiDAR imagery of the region:
Link LiDAR data courtesy of Dan Doctor, USGS.
14 January 2016
There’s something about Arctic and Antarctic adventure that stirs my interest. The merciless but fascinating environment, the odd fauna, the endurance, The Endurance, the way human frailties pop out against the stark backdrop. Evidently novelist Rebecca Hunt is subject to the same entrancement. She was one of 18 artists and writers who participated in the Arctic Circle residency in 2011, and I think it follows that the novel Everland resulted from that time. Everland, however, is set in the Antarctic, on an island off a cape of the continent (The island is named, in the first few sentences of Chapter 4, as “Everland.”). At first glance, the Arctic and the Antarctic could easily be traded for another, but in detail of course, they differ. Occasionally, small details betray this substitution of Hunt’s experience for the novel’s setting: the presence of “a pair of antlers” and a walrus skull on the exterior of the Antarctic scientific research base. Given the remoteness and expense of getting to Antarctica, it seems logical to presume these biological materials weren’t imported, and therefore the author may be mistakenly implying that they are found locally. However, there are no land mammals at all (much less hooved and antlered ones) on the continent of Antarctica. And the marine range of walruses is entirely limited to the Arctic and subarctic portions of the northern hemisphere.
When it comes to geology, I’m sad to report that it gets worse: One character nominally has geological predilections, but the accompanying details betray the intent of conveying specialist knowledge:
He’d stockpiled Antarctic specimens, including diorite quartz and kenyte lava…
It seems to me that quartz and diorite are perhaps transposed in that sentence, or perhaps a comma is missing. Kenyte, on the other hand, is legit, and a common rock type associated with Mt. Erebus. So that’s a good example of a sentence that I can both critique and that taught me something I didn’t know.
‘Quartz feldspar, an igneous rock created from lava,’ he said to Millet-Bass, showing his latest discoveries. ‘That one’s pegmatite, another magma rock.’
Readers of this blog don’t need to be told that quartz and feldspar are two different minerals (or really, mineral families), and that putting them next to one another doesn’t constitute a rock name.
Hunt’s description of glaciation, however, is far superior to her petrology:
Everland’s glacier had bulldozed a deep, highway-wide gorge through the island. As the weight of countless tons of compacted snow chewed into the bedrock, the loose debris which piled at its edges had amassed into thirty-meter-high moraine walls. These moraines acted as benchmark, showing how much the glacier had receded in modern times. The ice that would have once filled the gorge was now a thinner, lower flow which had shrunk back from its former margins, like a drought-stricken river. An as the ice’s edges retreated, borders of dry ground between the moraine and each side of the glacier were exposed, inviting the curious to enter.
But that’s all I really had to work with on a strictly geological level. This is a novel, not a nonfiction account. It weaves a tale of twin expeditions beset by injury and fatigue in the same place, a century apart. Each expedition has three participants, all with their individual flaws and strengths. How the earlier, historical expedition is remembered (who’s a ‘bad guy’ and who’s a victim) doesn’t match the reality that unfolds over the course of the book. And while public opinion isn’t a factor in the more modern group working on the island, in some ways their story is more approachable, since two of the three are scientists, and another two of the three are field work fiends. The structure basically tells two stories simultaneously, as Cryptonomicon did, but with a simple, elegantly sculpted approach.
What Hunt does really well is think through social dynamics and elegantly express them on the page. The mental calculations made about how to say a given thing, to who, and with what emphasis and what consequences, were the parts that made the book really shine. These passages of social agonizing felt real in a way that I never could express myself, and I can forgive a lot of mineral/rock terminology swappage if it means I get such a clean, clear look at the human condition.
8 January 2016
Pretty sweet, amiright? Thanks, Martin.
Happy Friday, all!
6 January 2016
Check this out:
That’s a big boulder (with my GigaPan for scale) at Marshall’s Beach, San Francisco, right around the corner from the Golden Gate Bridge:
The big boulder is mantled in colluvium derived from the weathering of the serpentinite mélange exposed along the beach here. I don’t know whether this boulder is close to its bedrock source point, or whether it’s a “knocker” that weathered out some tens of meters uphill, became incorporated into the colluvium, and has been on its way downhill for some time. Regardless, it’s on the move, and it has reached the beach. Unusual levels of rain and wave action the previous week undermined the boulder’s support from below, at the same time it “slushified” the colluvium above. The boulder then slipped a couple of feet downhill.
The evidence of this recent slip is the relatively pristine scarp above the boulder, wherein you can see serpentinite colluvial / soil horizons exposed in cross-section:
Let’s zoom in:
I shot two GigaPans of this scene:
Link Image by Callan Bentley
Link Image by Callan Bentley
While the GigaPan worked (several hours of time), I poked around and observed. Uphill and to the right (south), I noticed that the colluvium showed a lot of other small scarps that showed up when the light was right. Check them all out:
This is a hillside that is on the move! You would not want to be walking Marshall’s Beach during or immediately after a big rainstorm.