Big geology

It's easy to get overwhelmed when you start looking into geology.

Both the size scale and the time scale are so immense that it's hard to wrap your brain around them.  Huge forces at work, that have been at work for billions of years -- and will continue to work for another billion.  Makes me feel awfully... insignificant.

The topic comes up because of three recent bits of research into just how powerful geological processes can be.  In the first, scientists were studying a crater field in Wyoming that dates to the Permian Period, around 280 million years ago (28 million years, give or take, before the biggest mass extinction the Earth has ever experienced).  The craters are between ten and seventy meters in diameter, and there are several dozen of them, all dating from right around the same time.  The thought was that they were created when an asteroid exploded in the upper atmosphere, raining debris of various sizes on the impact site.

The recent research, though, shows that what happened was even more dramatic.

"Many of the craters are clustered in groups and are aligned along rays," said Thomas Kenkmann of the University of Freiburg, who led the project.  "Furthermore, several craters are elliptical, allowing the reconstruction of the incoming paths of the impactors.  The reconstructed trajectories have a radial pattern.  The trajectories indicate a single source and show that the craters were formed by ejected blocks from a large primary crater."

So what appears to have happened is this.

A large meteorite hit the Earth -- triangulating from the pattern of impact craters, something like 150 and 200 kilometers away -- and the blast flung pieces of rock (both from the meteorite and from the impact site) into the air, which then arced back down and struck at speeds estimated to be up to a thousand meters per second.  The craters were formed by impacts from rocks between four and eight meters across, and the primary impact crater (which has not been found, but is thought to be buried under sediments somewhere near the Wyoming-Nebraska border) is thought to be fifty kilometers or more across.

Imagine it.  A huge rock from space hits a spot two hundred kilometers from where you are, and five minutes later you're bombarded by boulders traveling at a kilometer per second. 

This is called "having a bad day."

[Image licensed under the Creative Commons State Farm, Asteroid falling to Earth, CC BY 2.0]

The second link was to research about the geology of Japan -- second only to Indonesia as one of the most dangerously active tectonic regions on Earth -- which showed the presence of a pluton (a large underground blob of rock different from the rocks that surround it) that sits right near the Nankai Subduction Zone.  This pluton is so large that it actually deforms the crust -- causing the bit above it to bulge and the bit below it to sag.  This creates cracks down which groundwater can seep.

And groundwater acts as a lubricant.  So this blob of rock is, apparently, acting as a focal point for enormous earthquakes.

The Kumano pluton (the red bulge in the middle of the image).  The Nankai Subduction Zone is immediately to the left.

Slipping in this subduction zone caused two earthquakes of above magnitude 8, in 1944 and 1946.  Understanding the structure of this complex region might help predict when and where the next one will come.

If that doesn't make you feel small enough, the third piece of research was into the Missoula Megaflood -- a tremendous flood (thus the name) that occurred 18,000 years ago.

During the last ice age, a glacial ice dam formed across what is now the northern Idaho Rockies.  As the climate warmed, the ice melted, and the water backed up into an enormous lake -- called Lake Missoula -- that covered a good bit of what is now western Montana.  Further warming eventually caused the ice dam to collapse, and all that water drained out, sweeping across what is now eastern Washington, and literally scouring the place down to bedrock.  You can still see the effects today; the area is called the "Channeled Scablands," and is formed of teardrop-shaped pockets of relatively intact topsoil surrounded by gullies floored with bare rock.  (If you've ever seen what a shallow stream does to a sandy beach as it flows into sea, you can picture exactly what it looks like.)

The recent research has made the story even more interesting.  One thing that a lot of laypeople have never heard of is the concept of isostasy -- that the tectonic plates, the chunks of the Earth's crust, are actually floating in the liquid mantle beneath them, and the level they float is dependent upon how heavy they are, just as putting heavy weights in a boat make it float lower in the water.  Well, as the Cordilleran Ice Sheet melted, that weight was removed, and the flat piece of crust underneath it tilted upward on the eastern edge.

It's like having a full bowl of water on a table, and lifting one end of the table.  The bowl will dump over, spilling out the water, and it will flow downhill and run off the edge -- just as Lake Missoula did.

Interestingly, exactly the same thing is going on right now underneath Great Britain.  During the last ice age, Scotland was completely glaciated; southern England was not.  The melting of those glaciers has resulted in isostatic rebound, lifting the northern edge of the island by ten centimeters per century.  At the same time, the tilt is pushing southern England downward, and it's sinking, at about five centimeters per century.  (Fortunately, there's no giant lake waiting to spill across the country.)

We humans get a bit cocky at times, don't we?  We're powerful, masters of the planet.  Well... not really.  We're dwarfed by structures and processes we're only beginning to understand.  Probably a good thing, that.  Arrogance never did anyone any favors.  There's nothing wrong with finding out we're not invincible -- and that there are a lot of things out there way, way bigger than we are, that don't give a rat's ass for our little concerns.

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People made fun of Donald Rumsfeld for his statement that there are "known unknowns" -- things we know we don't know -- but a far larger number of "unknown unknowns," which are all the things we aren't even aware that we don't know.

While he certainly could have phrased it a little more clearly, and understand that I'm not in any way defending Donald Rumsfeld's other actions and statements, he certainly was right in this case.  It's profoundly humbling to find out how much we don't know, even about subjects about which we consider ourselves experts.  One of the most important things we need to do is to keep in mind not only that we might have things wrong, and that additional evidence may completely overturn what we thought we knew -- and more, that there are some things so far out of our ken that we may not even know they exist.

These ideas -- the perimeter of human knowledge, and the importance of being able to learn, relearn, change directions, and accept new information -- are the topic of psychologist Adam Grant's book Think Again: The Power of Knowing What You Don't Know.  In it, he explores not only how we are all riding around with blinders on, but how to take steps toward removing them, starting with not surrounding yourself with an echo chamber of like-minded people who might not even recognize that they have things wrong.  We should hold our own beliefs up to the light of scrutiny.  As Grant puts it, we should approach issues like scientists looking for the truth, not like a campaigning politician trying to convince an audience.

It's a book that challenges us to move past our stance of "clearly I'm right about this" to the more reasoned approach of "let me see if the evidence supports this."  In this era of media spin, fake news, and propaganda, it's a critical message -- and Think Again should be on everyone's to-read list.

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Caught in the sea's net

The specter of climate change is getting difficult to ignore.  While you still can't point at a particular event and say "that happened because of anthropogenic climate change" -- as I said about a million times to my students, "climate isn't the same as weather" -- we've had enough anomalous heat waves, droughts, floods, and storms in the past ten years that it's getting harder and harder to deny unless you go around with blinders on or are just plain stupid.  (The latest being the catastrophic tornadoes that tore through Kentucky a couple of weeks ago, despite it being December, usually a low point in tornado occurrence and intensity.)

There are signs that even the science deniers are beginning to have some traces of second thoughts about the whole thing.  A study in Nature Scientific Reports a few weeks ago found that "climate contrarians" have of late begun to shift their ground, from outright denial that it's happening to attacking the researchers' integrities and the solutions they propose.  While this is still maddening to those of us who can actually read and understand a scientific paper, it's at least a tentative step in the right direction.  "I don't like the people who are saying this" and "the solutions won't work/are too expensive" are better than "this isn't happening" and "la la la la la la la not listening."

But the evidence that the situation is perilous keeps piling up.  One of the consequences of climate change most people don't think a lot about is sea level rise, mostly because the numbers seem insignificant; for example, a recent study showed that in the twenty-seven years between 1993 and 2020, the average sea level rose by a centimeter, and the rate of rise in the past ten years is triple what it was in the twentieth century.

It's easy to say, "a centimeter?  That's hardly anything."  But that ignores a couple of things.  First, that's an average; because of patterns of melt water, and sea and wind currents, some places have seen an increase of up to twenty centimeters, easily enough to cause devastating coastal flooding and infiltration of fresh-water aquifers with salt.  Second, there's geological evidence that when the sea level rises, it can happen in fits-and-starts, as ice shelves (primarily in Greenland and Antarctica) collapse.  Given how many people live in low-lying coastal areas, it wouldn't take much to cause a humanitarian catastrophe.

Another pair of studies that came out just last week have illustrated how vulnerable coastal communities have been -- and still are -- to changes in sea level.  Archaeologists uncovered evidence from two millennia ago in southern Brazil indicating that a drop in sea level due to increases in polar ice exposed shellfish beds that the coastal indigenous people depended on, and led to wide abandonment of settlements in the area.  The opposite happened in Greenland in the fourteenth century -- coastal communities that had been settled by Vikings three centuries earlier got swamped, eradicating coastline and driving the settlers up against uninhabitable glacial regions.  They were caught between the rising seas and the rising ice, trapped in an ever-shrinking strip of land that eventually disappeared completely.

[Image licensed under the Creative Commons Jensbn, Greenland scenery, CC BY-SA 3.0]

My initial reaction to the latter paper was puzzlement; the fourteenth century was the height of the Little Ice Age, so you'd think the freeze-up would have lowered sea level, not raised it.  But I was failing to take into account isostasy, which is the phenomenon caused by the fact that the continents are literally floating in the magma of the mantle.  Just like adding weight to a boat causes it to ride lower in the water, adding weight to a continent causes it to sink a little into the mantle.  So when the ice sheets built up on Greenland, it pushed it downward, submerging habitable coastline.  (The opposite has happened as the glaciers have melted; in fact, it's still happening in Scandinavia, Canada, and Scotland, the latter of which is still undergoing isostatic rebound at a rate of ten centimeters of uplift per century.)

The deniers are right about one thing; the Earth has certainly experienced climatic ups and downs throughout its long history.  What's terrifying right now is the rate at which it's happening.  A study from the International Panel on Climate Change found persuasive evidence that the rate of temperature increase we're seeing is higher than it's been since the Paleocene-Eocene Thermal Maximum, over fifty million years ago.

If that doesn't scare you, I don't know what would.

It's the humanitarian cost that's been on my mind lately, not just because of today's climate change, but the changes that have occurred historically.  I was so captivated by the tragedy of the disappearance of the Norse settlements in Greenland that years ago, it inspired me to write a poem -- one of the few I've ever written.  What would it be like to be the last person alive in a place, knowing no one would come to rescue you?  I can only hope humanity's fate won't be so bleak -- but whenever I think about our reckless attitude toward the environment, this haunting image comes to mind, and I thought it would be a fitting way to end this post.

Greenland Colony 1375

He goes down to the sea each day and walks the shore.
Each day the gray sea ice is closer, and fewer gulls come.
He wanders up toward the village, past the empty and ruined rectory.
The churchyard behind it has stone cairns.  His wife lies beneath one,
And there is one for Thórvald, his son,
Though Thórvald's bones do not rest there; he and three others
Were gathered ten years ago in the sea's net
And came not home.

Since building his son's cairn,
He had buried one by one the last four villagers.
Each time he prayed in the in the stone church on Sunday
That he would be next,
And not left alone to watch the ice closing in.

In his father's time ships had come.  The last one came
Fifty years ago.
Storms and ice made it easy for captains to forget
The village existed.  For a time he prayed each Sunday
For a ship to come and take him to Iceland or Norway or anywhere.
None came.  Ship-prayers died with the last villager,
Three years ago.  He still prayed in the stone church on Sunday,
For other things; until last winter,
When the church roof collapsed in a storm.
The next Sunday he stayed home and prayed for other things there.

Now even the gulls are going,
Riding the thin winds to other shores.  Soon they will all be gone.
He will walk the shore, looking out to sea for ships that will never come,
And see only the gray sea ice, closer each day.

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I remember when I first learned about the tragedy of how much classical literature has been lost.  Take, for example, Sophocles, which anyone who's taken a college lit class probably knows because of his plays Oedipus Rex, Antigone, and Oedipus at Colonus.  He was the author of at least 120 plays, of which only seven have survived.  While we consider him to be one of the most brilliant ancient Greek playwrights, we don't even have ten percent of the literature he wrote.  As Carl Sagan put it, it's as if all we had of Shakespeare was Timon of Athens, The Merry Wives of Windsor, and Cymbeline, and were judging his talent based upon that.

The same is true of just about every classical Greek and Roman writer.  Little to nothing of their work survives; some are only known because of references to their writing in other authors.  Some of what we do have was saved by fortunate chance; this is the subject of Stephen Greenblatt's wonderful book The Swerve, which is about how a fifteenth-century book collector, Poggio Bracciolini, discovered in a monastic library what might well have been the sole remaining copy of Lucretius's masterwork De Rerum Natura (On the Nature of Things), which was one of the first pieces of writing to take seriously Democritus's idea that all matter is made of atoms.

The Swerve looks at the history of Lucretius's work (and its origin in the philosophy of Epicurus) and the monastic tradition that allowed it to survive, as well as Poggio's own life and times and how his discovery altered the course of our pursuit of natural history.  (This is the "swerve" referenced in the title.)  It's a fascinating read for anyone who enjoys history or science (or the history of science).  His writing is clear, lucid, and quick-paced, about as far from the stereotype of historical writing being dry and boring as you could get.  You definitely need to put this one on your to-read list.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]