5 February 2014
Bob Hazen, the prolific and multitalented scientist from the Carnegie Institution of Washington and George Mason University, put a new book out recently, and I just read the paperback version of it. The book’s title reveals its subject matter plainly enough: the story of our planet over geologic time. As such, it’s an exercise in Historical Geology, and because I’m not satisfied with any of the Historical Geology textbooks on the market, I decided to read this partly for fun (as I would any nonfictional popular science book) but also as potentially a replacement “text” for my Historical classes. How could I not be enticed by enthusiastic passages such as this?
And so I have become a compulsive reader of the testimony of the rocks — the compelling, if sometimes fragmentary and ambiguous, stories they have to tell of birth and death, of stasis and flux, of origins and evolution. This untold grand and intertwined tale of Earth’s living and nonliving spheres — the coevolution of life and rocks — is utterly amazing. It must be shared, because we are Earth. Everything that gives us shelter and sustenance, all the objects we possess, indeed every atom and molecule of our flesh-bound shells, comes from Earth and will return to Earth. To know our home, then, is to know part of ourselves.
That is a beautiful sentiment, one I would heartily label as geo-philosophy, with no disparagement implied in that label. This is one of the things I find so very satisfying about geoscience: how it informs our grander sense of perspective on our own existence, indeed, the very matter from which we are made.
It’s a good book, a good read, and the science is both compelling, and presented compellingly. I give the book overall a thumbs-up. I enjoyed reading it more than I did Genesis, his account of the origins of life on Earth, perhaps because the scope was broader in terms of scientific stories, and perhaps because it was less personal. In both books, Hazen describes his role in elucidating the past. This is entirely appropriate, but it creates a sort of distorted view of geoscience, with a disproportionate amount of time spent on one person’s contributions (and, to a lesser extent, the contributions of Hazen’s professional colleagues), as compared to the general advancement of scientific understanding. On the other hand, these anecdotes of methodology and insight (and even bickering with peers) provide genuine insight into the process of science, perhaps a matter of greater importance for the lay reader than the specific conclusions arrived at by the scientists.
Some of good stuff:
The timescale in the book is presented in the opposite way from the conventional point of reference being us, in our time. Rather than saying “so and so many years ago,” Hazen starts at the beginning, and says things like “When the Earth was 100 million years old,” instead. He’s counting forward rather than backward. This is subtle, but equally legitimate, and it puts one in mind of the grand theme which motivated the book – the story of change over time, especially the interaction between parts of the Earth system which results in changes in the mineral species which can form on Earth.
I liked the fresh take on the age of the Earth. Hazen cleverly compares 4.5 billion seconds (~144 years), which is a couple decades longer than even the longest known human lifetime, to 4.5 billion minutes (~8500 years), which is longer than recorded human history, to 4.5 billion years, which of course is approximately the age of the planet (and the solar system of which it is a part).
On page 56, I found an example of what I would call “Classic Hazen:”
Most of us think of oxygen, first and foremost, as an essential part of the atmosphere (the 21 percent or so that keeps us alive). But the happy atmospheric development is a relatively recent change in Earth history. For Earth’s first two billion years at least, the atmosphere was utterly devoid of oxygen. Even today almost all of Earth’s oxygen — 99.9999 percent of it — is locked into rocks and minerals. When you hike up a majestic, rugged mountain, or walk on a windswept rocky outcrop, most of the atoms beneath your feet are oxygen. When you lie on a sandy beach, almost two in three of the atoms that support your weight are oxygen.
That is awesome. That’s a turn of phrase which changes the way you look at the world. It’s because of descriptions like that, that we need more writers like Bob Hazen.
On page 158, he offers the best explanation of mass independent fractionation of sulfur isotopes that I’ve yet read. If you’re wondering why anyone would care about such a thing, I’d refer you to the work of James Farquhar. Basically: by looking at the mass number of sulfur isotopes, you can find an odd effect: masses that are odd (33, say, vs. 32 or 34) are selectively affected by ultraviolet radiation. Ozone (a byproduct of the oxygenation of the atmosphere), screens out UV radiation. So you’d expect to see a shift in the proportion of sulfur-33 when the atmosphere gets sufficiently oxygenated to make ozone. Though I’ve been hearing about mass independent fractionation for years (Farquhar works at the University of Maryland, where I got my geology master’s), reading Hazen’s book was the first time the idea really made sense to me.
I also really appreciated the deep dive into chondritic meteorites. I don’t know enough about meteorites in general, and therefore neither do I know enough about chondrules, these odd little sphere-like rock bodies that represent some of the oldest macroscopic objects in our solar system.
Another new insight of the scientific sort was the connection between oxygenation of the atmosphere and biologically-catalyzed production of clay minerals in the aftermath of the Snowball Earth glaciations in the Neoproterozoic era of geologic time. I’ve never been satisfied with the explanations for the coincidence of oxygenation and deglaciation, but this helped me connect two previously isolated phenomena together in my own mind.
The book’s editor should have caught some instances of repeating the same phrase or sentence multiple times. For instance on egregious example is when on pages 2-3, Hazen writes, “The formation of the massive Hawaiian Islands required slow and steady volcanic activity, successive lava blankets piling up over millions of years. The Appalachians and other ancient rounded mountain ranges are the result of hundreds of millions of years of gradual erosion punctuated by great landslides,” and then on page 28, he says, “The massive Hawaiian Islands required slow and steady volcanic activity, as successive lava blankets piled up — at least tens of millions of years, based on modern rates of eruption. The Appalachians and other ancient rounded mountain ranges were formed by hundreds of millions of years of gradual erosion.” The two are not verbatim repetitions, but certainly the concept is, and the wording is a very close match. I don’t fault Hazen for this, because I think it’s inherent to human thought process to default to a particularly apt chain of words, especially if we teach – it’s easy to fall into a well-worn groove of thinking, latching on to a resonant analogy or turn of phrase. But that’s why we have editors, to screen out those mistakes.
Here’s something more fundamental: On page 119, speaking of the oceanic ridge system, Hazen says this:
But between adjacent blocks the pattern is broken, offset by transform fault lines and skewed like a cubist painting.
This raises a red flag for me as a structural geologist. No, I’m not talking about his use of “fault line,”that phrase a perpetual bugbear of mine, but the implication that the ridges of the oceanic ridge system are themselves offset – that is to say, they were once continuous, but then later, they were broken and moved in opposite directions like a sedimentary stratum disrupted and displaced along a subsequent normal fault. Technically, the sentence is true – “the pattern” being its literal subject. But while the pattern may be broken, that doesn’t indicate the ridges are truly displaced. Is that what he’s actually saying? Unfortunately, the following sentences suggest the answer is yes:
Analysis of offsets along one of these faults, the Mendocino Fracture Zone, reveals a remarkable lateral displacement of seven hundred miles. Epic internal processes must be at work to so disrupt Earth’s crust.
What I think I’m reading here is what I feared: a misunderstanding of what oceanic ridge systems and their intermingled transform fault zones represent. Rather than one continuous smooth ridge that was later broken into segments and those segments shifted relative to one another, the ridge system instead represents the natural pattern that results when a transtensional boundary (such as Pangaea splitting down the middle) is resolved through seafloor spreading. Harland (1971) defined transtension in the same paper he coined transpression, and he illustrated it in a clever way: a map view of two plates. One, octagonal in map view, was wholly contained within the boundaries of the other, but was moving overall in the opposite direction. What sorts of plate boundaries would result?
As you see, there is a classic convergent boundary in the “west,” and a classic divergent boundary in the “east.” Along the “northern” and “southern” margins of the smaller plate, you see classic transform plate boundaries, one left-lateral, and the other right-lateral. It’s the diagonal edges where transpression and transtension occur. Note that transtension takes an initially “northeast/southwest” striking boundary and accomodates the stresses with a jagged “stairstep” pattern of alternating transform faults and spreading ridges. Obliquely opening a spreading center and maintaining the northeast-southwest orientation is inefficient, and does not occur. In other words, you see Point A (marked in red) and Point B? They are always in that same fixed position relative to one another (A southwest of B); It is not true that A was once located due south of B, but was later shifted to the west along a series of transform faults.
The book does not contain a Works Cited or recommended reading section, nor do any footnotes point to the specific studies (such as this Mendocino one) that Hazen references. While I think that’s probably a good call for a popular science work, it frustrates me in this instance to not be to be able to directly examine the study in question. I wanted to make sure there wasn’t something special about the Mendocino Fault Zone that presents a special case where in fact there is major offset. To make sure I wasn’t leading my readers astray, I checked the site on Google Earth…
… and verified that only the section between the Mendocino Triple Point and the southern edge of the Gorda Ridge is actively moving (as indicated by earthquake epicenters):
This seems to me to be a fairly ordinary example of a transform boundary, at least as far as the Gorda Plate and the Pacific Plate are concerned. Maybe I’m missing something key here, some extraordinary aspect to the Mendocino Fracture Zone that implies it truly is responsible for displacing some originally-continuous marker unit. If so, I trust someone among you will clue me in?
Anyhow, to be sure, there are epic internal processes at work, and in many places Earth’s crust is indeed disrupted, displaced, and its pieces translated in opposite directions. But I’d rather look at a transform fault in continental crust such as the San Andreas (California), the North Anatolian (Turkey), or the Alpine (New Zealand) for those sorts of true offsets.
Okay, moving on… One final quibble!
On page 201, he discusses the media frenzy that surrounded his publication with colleagues of the idea of mineral evolution in 2008. He notes that:
The New Scientist even published a clever cartoon showing four “stages” of mineral evolution, from a swimming crystal with fins to an “evolved” crystal with a walking stick.
Again, I think Dr. Hazen’s editor should have done some fact-checking here. The magazine in question was not New Scientist (note no “the”); it was EARTH magazine. I know, because I was the guy who drew the cartoon. Here it is:
I was particularly satisfied when I drew this one. What rankles me personally about the reference in the book is that I know the cartoon wasn’t merely a blip on his radar. Hazen liked the cartoon so much, he contacted me through EARTH (though we were both teaching geology at GMU that semester, I had never met him in person), and asked to buy it. I sold it to him. Presumably, it hangs on his office bulletin board somewhere, an artifact divorced from its origins and context.
Oh well. I’m glad it made him smile, and I’m glad that it was mentioned in his book.
The book is worth reading. Parts of it will change the way you look at your planet. You should put it on your list.
Harland, W. B., 1971. Tectonic transpression in Caledonian Spitsbergen. Geological Magazine 108, 27-42.
3 February 2014
This past week, there’s been a beautiful sight along the stretch of the Fort Valley Road that goes past the Blue Hole section of Passage Creek.
Ice has been forming beautiful forms as groundwater seeps out along bedding planes in the Massanutten Sandstone (a Silurian-aged quartz arenite, folded during late Paleozoic Alleghanian deformation). At this site, the bedding dips moderately to the south. This is close to the axis of the Massanutten Synclinorium. Here’s a look at the bedding highlighted:
And here are a few shots showing the variety of icy forms at the site:
Finally, here’s another high-speed commuting video, which features some regular-speed footage of the ice seep site, starting at 1:38. Enjoy!
31 January 2014
Todd Redding is our genorous sponsor for this week’s Friday fold.
Todd reports that this boulder is derived from the Okanagan Metamorphic Complex near Penticton, British Columbia, Canada. He gives its lat/long as 49°28’14.10″N, 119°30’23.14″W.
Did you spot the small fault in there, too?
Thanks for sharing, Todd!
30 January 2014
One of the intriguing rocks you find in Virginia, at the interface between the Valley and Ridge province and the Blue Ridge province, is distinctive brecciated Antietam Formation. The Antietam (sometimes known as the “Erwin,” especially in Shenandoah National Park), is a quartz arenite (quartz sandstone) that has been variably fused to quartzite in some places (but not others). It’s been deformed, sometimes spectacularly so, as we see when the individual grains have been (ductilely) stretched out into little blimp shapes, all aligned due to pressure solution.
In other places, it’s seen to have experienced a different kind of deformation, a brittle sort. In places, the Antietam is shattered, and then the resulting shards have been stuck back together into solid rock. This turns it into a breccia. Sometimes the breccia is cemented by quartz (same color as the clasts), and sometimes it’s stuck together with iron and manganese oxide minerals (which are dark brown or blackish). The latter is a high-contrast beauty. Here, you can examine this intriguing rock in outcrop and in hand sample via the magic of GigaPans:
How did this breccia form? There are many kinds. This one is neither a sedimentary breccia (for instance, made from sediment that accumulates at the base of a cliff), nor a volcanic breccia (which is lithified lahar deposits or pyroclastic surge deposits). One explanation is that it’s a tectonic breccia, the crushed up rock that formed along a fault zone. The contact between the Blue Ridge and the Valley & Ridge is indeed a thrust fault in some places. However, this outcrop and this sample, from the Boyce quadrangle, are from west of the floodplain of the Shenandoah River, in a section of the quad where there is no missing stratigraphic section – in other words, the “stack” of Blue Ridge layers goes “seamlessly” up (west) into the strata of the Valley & Ridge. This map pattern suggests there is no “need” for a fault to be postulated in this particular area. Another possibility is that this is a collapse breccia, wherein an adjacent carbonate unit dissolved away, then the Antietam broke into that void, shattering and scattering, and later fluid flow filled in the gaps between the pieces. Maybe it’s a dialational breccia, wherein a jog in the stress field ripped open a low-pressure area during Alleghanian deformation, and *kapow* the Antietam’s brittle bits exploded into that pocket.
Or some combination of all of these? Take a moment to explore these images (the deeper you go, the more detail you get), and let me know what you think.
Food for thought – some previous posts on this blog that discuss brecciation in the Antietam:
29 January 2014
It’s another cold morning in the Fort Valley. To celebrate winter’s continuing grip, please enjoy these images from last Friday morning, on my way to work…
Frost on plants:
Frost on barbed wire:
Finally, here’s a time-lapse video (5 times actual speed) of the first 6 miles of my commute (walking, then driving):
24 January 2014
Reader Eric Fulmer contributed this week’s Friday fold. It’s a beauty!
Eric writes that this outcrop is from “the Belgian Ardennes near Durbuy. There’s a well-exposed anticline along the Ourthe River. The stone is late-Devonian limestone typical of the immediate area that was later deformed regionally due to the Variscan orogeny. The Ardennes are classic fold-and-thrust belt, much like our Valley-and-Ridge province.”
Very cool indeed. Thanks for sharing, Eric!
21 January 2014
I was first alerted to the proposal of a new bill in the Virginia House of Delegates last Wednesday by a colleague at James Madison University, Eric Pyle. Eric and I serve as state Councilors for the state of Virginia in the National Association of Geoscience Teachers. As such, we are sincerely concerned about any policy that would weaken science education in the Old Dominion, in particular when it comes to geoscience literacy. The proposed bill, HB 207, would allow creationist teachers to pass creationism off as science. It would undermine the state’s solid record of science education and imperil the utility and employ-ability of Virginia’s science graduates in the economy of the future. We agree that this bill is pernicious at worst, and unnecessary at best. It should not pass the House, nor be ratified into law.
This morning, I got an email from the National Center for Science Education on the subject of the pending legislation. I repeat it in its entirety below by way of spreading the word to a wider audience. I trust NCSE won’t take issue with this “signal boost.” Here it is, and more discussion follows:
Here is the language of the bill in its entirety:
HOUSE BILL NO. 207
Offered January 8, 2014
Prefiled December 27, 2013
A BILL to amend the Code of Virginia by adding a section numbered 22.1-207.6, relating to instruction in science.
Patron– Bell, Richard P.
Referred to Committee on Education
Be it enacted by the General Assembly of Virginia:
1. That the Code of Virginia is amended by adding a section numbered 22.1-207.6 as follows:
§ 22.1-207.6. Instruction in science.
A. The Board and each local school board, division superintendent, and school board employee shall create an environment in public elementary and secondary schools that encourages students to explore scientific questions, learn about scientific evidence, develop critical thinking skills, and respond appropriately and respectfully to differences of opinion about scientific controversies in science classes.
B. The Board and each local school board, division superintendent, and school board employee shall assist teachers to find effective ways to present scientific controversies in science classes.
C. Neither the Board nor any local school board, division superintendent, or school board employee shall prohibit any public elementary or secondary school teacher from helping students understand, analyze, critique, and review in an objective manner the scientific strengths and scientific weaknesses of existing scientific theories covered in science classes.
D. Nothing in this section shall be construed to promote or discriminate against any religious or nonreligious doctrine, promote or discriminate against a particular set of religious beliefs or nonbeliefs, or promote or discriminate against religion or nonreligion.
2. That no later than August 1, 2014, the Board of Education shall notify each division superintendent of the provisions of this act. Each division superintendent shall notify all employees of the local school board of the provisions of this act by the first day of the 2014-2015 school year.
Encourage students to explore scientific questions? Learn about evidence? Develop critical thinking skills? Delegate Bell, we already do exactly that! That’s exactly what my colleagues and I strive to do every day to produce graduates who will be ready to take their place on the cutting edge of scientific jobs. So clearly, that’s not what this is all about.
The intention of this bill is to allow unscientific beliefs into science classrooms. It’s the sort of anti-science initiative that makes me cringe for the reputation of my home state.
Delegate Bell’s website insists that he wants to:
- Be a leader for education reform and affordable college education.
- Push for expanded career and technical education training.
- Work to reduce the size of government.
The problem is that HB 207 violates all three of these aims.
- House Bill 207 would hamper the quality of education in the Commonwealth of Virginia by infusing a class dedicated to empirical reason with the idiosyncratic politics of individual instructors. When my colleagues and I at the college level then get students from Virginia public schools in our science classrooms, we’re going to have a tougher time counteracting their confusion, and this will make college education less effective and therefore more expensive to achieve the same level of mastery.
- If we want Virginia’s graduates to be contributors and leaders in the global economy, they need to emerge from school unblinkered by superstition and unbrainwashed by the politics of their elders. For them to succeed in science and technology careers, we need them to be data-driven, and capable of logical coherence that transcends individual mythologies and ideologies with verifiable facts. We do not want them confusing their familial belief system or some politically-inspired gobbledygook with peer-reviewed assessments of reality. HB 207 will hamstring Virginia’s science students, ensuring that the Commonwealth will fall behind in science and contributions to the nation’s economy. This bill’s passage would mean that some other state will be producing tomorrow’s leaders in science and technology.
- Because this bill is unnecessary, passing the legislation would needlessly increase the bulk of Virginia statute law. Additionally, because the bill calls for “each local school board, division superintendent, and school board employee” to assist the anti-science teachers in their efforts, it directly adds responsibilities to the jobs of thousands of state employees, making them less efficient and less worth the state’s investment of tax dollars.
When I hear the language of HB 207, here’s what I hear Delegate Bell saying:
I work for the Commonwealth of Virginia as a science educator. I think HB 207 is a very, very bad idea for the science education of our students. I encourage my fellow Virginians to contact the members of the Subcommittee on Elementary and Secondary Education today and urge them to quash it.
Again, the names, emails, and phone numbers of the relevant legislators are:
Richard P. “Dickie” Bell, chair, (804) 698-1020
Robert H. Brink, (804) 698-1048
Mark L. Cole, (804) 698-1088
Peter F. Farrell, (804) 698-1056
Daun Sessoms Hester, (804) 698-1089
James LeMunyon, (804) 698-1067
Scott Lingamfelter, (804) 698-1031
Joseph Morrisey, (804) 698-1074
Brenda L. Pogge, (804) 698-1096
18 January 2014
I got a comment the other day on an old post on this blog, one showing beautiful cross-bedding at Zion National Park. These are dune sands – windblown at the time of deposition, and cemented in place for millions of years thereafter. These are petrified sand dunes!
The commenter asked about annotation, so I took ten minutes and modified the picture to highlight the key features as I saw them. Here’s the original…
And here’s the annotation:
I kind of like how that came out. It reminds me of stained glass!
I didn’t draw arrows on showing which way the wind must have been blowing in order to deposit this sand with cross-bedding in the orientation seen (dipping to the left).
In my mind there are multiple stages to the photo annotation process, and at this point I’ve tried to stay strictly observational, without dipping into interpretation. Wind current direction would be an example of information extracted from the raw, basic observations. It’s a higher-order sort of data.
So, students: Can you figure out which way it must have been blowing?
17 January 2014
Another guest Friday fold – again, from the structural geologist Christie Rowe at McGill University in Montreal:
Christie describes this as: growth faulting in beautiful fluvial sediments… Accordingly, I have squinted and annotated it a bit:
16 January 2014
While at the University of Texas at Austin, where the Jackson School of Geosciences was hosting the Summit on the Future of Geoscience Education this past weekend, I was impressed to see a well-developed rock garden outside the student center. Here’s an example of a stretched-pebble conglomerate from that garden:
Note the nice epidote boudins running down the middle. The way the foliation “flares” at the bottom suggests another boudin just beyond this sample’s “field of view”
This is the second of two stretched pebble conglomerates seen on campus in Austin. The first one was here.