The story of the Scablands

After my rather cataclysmic posts about geology last week, which looked at the volcano off the Greek island of Thera and the fault just waiting to rupture near the Pacific Northwest, one of my friends and a long-time loyal reader of Skeptophilia asked me if I'd ever done a post on the "Channeled Scablands."  I told him I'd mentioned it once or twice, but always in passing.

So as befits a catastrophe so big it beggars belief, I thought a more thorough look was warranted.

There's a bizarre bit of terrain in what is now eastern Washington and Oregon that goes by the rather horrid-sounding name my friend referenced, and if you ever fly over it, you'll see why.  It's formed of teardrop-shaped pockets of relatively intact topsoil surrounded by gullies floored with bare rock.  The terrain has the look of what a shallow stream does to a sandy beach as it flows into sea, only on a gargantuan scale:

[Image licensed under the Creative Commons DKRKaynor, Channeled Scablands, CC BY-SA 4.0]

Then there's Dry Falls, in the upper Grand Coulee Basin, which even has a plunge pool basin at its foot... but almost no water:

[Image licensed under the Creative Commons © Steven Pavlov / http://commons.wikimedia.org/wiki/User:Senapa / CC BY-SA 3.0, Dry Falls (Washington), CC BY-SA 3.0]

Geologists figured out pretty quickly that the entire terrain was sculpted by a huge amount of running water.  But the problem is, the entire area is a desert, and apparently has been for a long while.

So where'd all the water come from -- and where did it go?

The answer turned out to be the Missoula Megaflood -- a tremendous flood (thus the name) that occurred eighteen thousand years ago, and which is right up there with Thera and the Cascadia Subduction Zone on our list of things that are big and scary and can kill you.

What apparently happened is that during the last ice age, a glacial dam formed across the northern Idaho Rockies, blocking the outflow of what are now the Columbia, Snake, Okanogan, Pend Oreille, and Spokane Rivers.  As the climate warmed, the ice melted, but all that water had nowhere to go, so it backed up into an enormous lake -- called Lake Missoula -- that covered a good bit of what is now western Montana. 

As the ice age ended, the warming continued.  Eventually this 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. 

What made the flood even worse was a phenomenon called isostasy.  We're used to thinking of the tectonic plates as moving back and forth, more or less parallel to the Earth's surface, but what is less obvious is that they can also move up and down -- perpendicular to the surface, like ice cubes bobbing in a glass of sweet tea.  These chunks of the Earth's crust are actually floating in the semi-solid mantle beneath them, and the level they float is dependent upon how heavy they are, just as putting heavy weights in a boat makes it float lower in the water. 

Well, as the Cordilleran Ice Sheet melted, that weight was removed, and this caused the flat piece of crust underneath it to lift upward on its eastern edge.

The whole western corner of the United States tilted toward the Pacific Ocean.  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.

The result was a colossal flood that at its peak was traveling at an estimated one hundred kilometers an hour.  Dry Falls was, at that point, an enormous waterfall five times the width of Niagara Falls, with a flow rate ten times higher than all of the rivers in the world combined.

[Nota bene: This sort of isostatic tilt is still going on today, most notably 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.  The problem is, the whole country is connected (however a lot of Scottish people might wish otherwise), so the entire island is tipping like a teeter-totter.  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.]

These kinds of megafloods aren't uncommon, usually during the transition between a glacial and an interglacial period.  Another place this happened is not far from where I live -- around thirteen thousand years ago, there was an ice dam across what is now the St. Lawrence River, blocking the main outflow from the Great Lakes.  This backed all that water up into a huge lake called Lake Agassiz, which encompassed all of the Great Lakes and then some.  It was the same story as Lake Missoula; as the climate warmed, the ice dam collapsed, and a large percentage of the water drained out into the North Atlantic.  Some climatologists think that this may have been responsible for the Younger Dryas event, when the warming trend in North America suddenly reversed, the temperatures dropping in only a few decades by an estimated 7 C -- because all that fresh water temporarily shut down the North Atlantic Meridional Overturning Circulation, stopping the Gulf Stream in its tracks and sending eastern North America, Greenland, and western Europe back into the deep freeze for over a thousand years.  (The link between the draining of Lake Agassiz, the Younger Dryas, and the shutdown of the NAMOC is far from settled, however.)

This sort of thing, besides being fascinating in its own right, always makes me think of the people who talk about Earth being "fine tuned" for human habitation.  When you start looking into geology, climatology, and astronomy, you realize how tenuous our existence actually is.  That we've done as well as we have, despite all the natural calamities, is impressive, but our continued survival is hardly guaranteed.  We'd better start understanding the past history of our home, including the violent and uncomfortable bits -- lest our own reckless and heedless actions trigger a catastrophe we're ill prepared to deal with.

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Confidence, impacts, and ice ages

One of the most common misunderstandings about science by laypeople centers around the concept of degree of confidence.

This misunderstanding can be summed up that "all unproven hypotheses are equally likely."  You hear it with lots of loopy ideas -- that (for example) because we don't have strong evidence one way or the other regarding the existence of an afterlife, it's on the same footing as other phenomena for which we have no direct evidence, such as dark matter, time travel, and the claim we've been visited by extraterrestrials.

Another way this shows up is the dismissive, "all of this could be proven wrong tomorrow" attitude toward science.  The fact that new discoveries have on occasion overturned what we thought we understood is taken as evidence that all of science is on thin ice, that it's all equally tentative.  But this rests on a serious misapprehension about the reliability of evidence.  It's true that, as Einstein allegedly put it, "one experiment could prove wrong" either the Second Law of Thermodynamics or our understanding of the mechanisms of quantum entanglement; but the first is extremely unlikely (the Second Law is one of the most extensively-tested scientific principles known, and there has never been a single exception found to it) while even the physicists would admit the second is a possibility (we're still elucidating the idea of quantum entanglement, and new and intriguing data is being added to our understanding on nearly a daily basis).

This frustrates people who like to have certainty, or at least like to be able to say with confidence that something isn't possible.  I ran into an especially good example of this just yesterday when I was reading an article about the Younger Dryas, a mysterious climatological reversal that occurred 12,900 years ago and lasted only 1,200 years -- a mere blip on the geological time scale.  What happened was that during a period when the Earth was warming, in only a few decades the average temperature of the Earth dropped by an average of four degrees Celsius, enough to put most of the Northern Hemisphere back in the deep freeze.  (The event is named after a plant, Dryas octopetala, which only grows in extremely cold places, and which became common across Europe and North America through the duration of the temperature drop.)

[Image licensed under the Creative Commons Opioła jerzy, Dryas octopetala a4, CC BY-SA 3.0]

Of course, presented with such a conundrum, the first question that comes up is "Why did this happen?"  There are three main hypotheses:

• As the Earth was warming up after the last major glaciation, a huge freshwater lake that had piled up behind an ice dam was suddenly emptied when the dam collapsed.  This lake, nicknamed "Lake Agassiz," emptied out through what are now the St. Lawrence and Mackenzie Rivers, and caused a slowdown (or complete cessation) of the thermohaline circulation.  Put simply, this is the engine that powers the Gulf Stream, which brings warm water northward and keeps the northeastern United States and most of western Europe relatively temperate.  When the flood occurred, the north end of the thermohaline circulation became too fresh to sink, and the whole system ground to a halt, propelling us into another ice age.  It was only after a thousand years had passed, and the lake water had adequately mixed with the ocean water, that the circulation rebooted and things warmed back up.
• 12,900 years ago, the Earth was hit by an object from space -- probably either a comet or a meteorite -- and that collision flash-burned a significant fraction of the vegetation in northern North America.  The debris and ash blocked sunlight, cooling down the surface of the Earth and halting the warm-up we'd been experiencing in its tracks.  Eventually the ash settled out, the forests regrew, and the climate restabilized, but that took several centuries.
• A supernova in the constellation of Vela created a burst of radiation that destroyed the Earth's ozone layer and killed most of the Earth's megafauna, including mammoths, mastodons, dire wolves, and several species of temperate-climate camels, rhinos, and hippos.  The gamma radiation striking the atmosphere caused a cascade of chemical reactions that disrupted the balance of nitrogen-containing compounds (such as nitrous oxide and nitrogen dioxide), and this caused a sudden and drastic temperature drop.

Each has some points in its favor.  The ice-dam proponents argue that the temperature drop wasn't as fast as you'd expect from something catastrophic like a collision or supernova, and that in fact the extinctions that occurred were in species that had already been declining for millennia.  Scientists supporting the impact hypothesis were buoyed by the discovery of a previously-unknown crater in Greenland -- but they've been unable to pinpoint its age any more accurately than "some time between three million and twelve thousand years ago."  The supernova enthusiasts point to the existence of "black mats" -- thin layers of the remnants of anaerobic organisms -- as evidence that something drastic happened to the atmosphere at the beginning of the Younger Dryas, and samples taken from it do seem to have skewed nitrogen content.  (This same evidence is considered support for the impact hypothesis, because there have been "microspherules" -- tiny spheres of melted and refrozen metal -- found in some of those boundary layers.)  But the black mats in different locations seem to date from different time periods, with only three of the thirteen studied being coincident with the Younger Dryas event.  And most of the black mats studied don't contain microspherules.

So the argument is still out there.  As far as my own opinion, I can only say that I'm neither a paleoclimatologist nor an astrophysicist, so am unqualified to weigh in (and my opinion wouldn't mean much anyway).  It seems like the dam collapse model is the one that currently has the most support, but -- like all science -- new information could tilt us toward one of the others.

Why does this come up with regards to our confidence in scientific models?  Not only because it's a great example of competing explanations and the fact that good scientists are willing to entertain the possibility of alternate solutions to the conundrums they study.  The idea for this post came to me because of another twist on the Younger Dryas -- this one from noted wingnut Graham Hancock, who says that the Younger Dryas event not only inconvenienced the camels and dire wolves, it also wiped out an advanced technological civilization...

... which gave rise to the myth of Atlantis.

So this is what I mean about levels of confidence.  No, we haven't been able to rule out two of the three models for the cause of the Younger Dryas with any real certainty.  But the fourth idea -- that whatever caused the event also destroyed Atlantis -- has nothing, not a shred of evidence, to support it.  As the brilliant skeptic Jason Colavito put it:

[R]egardless of whether a comet hit, the existence (or non-existence) of the comet implies nothing about the existence of Atlantis any more than it would unicorns or leprechauns. 

It remains a point of astonishment that the bones of megafauna that supposedly died in the comet strike turn up with regularity, but every human being and all of the buildings, tools, and material possessions of the lost Atlantis-like civilization were blasted clean off the face of the Earth, without a single trace remaining.  I have trouble imagining that a sloth can manage to have its bones preserved for all time, but not a single outpost of Atlantis had even a single bolt or screw remain.

As do I.  All unproven assertions are not on an equal footing.  And that's really the point of Ockham's Razor, isn't it?  The fastest way to winnow down competing ideas is to see which ones require you to make the most ad hoc assumptions.  And I'd put any of the three scientific explanations I mentioned above ahead of Hancock's assertion that the Younger Dryas event destroyed the lost civilization of Atlantis.

I'm perfectly willing to stay in uncertainty, indefinitely if need be, in the absence of convincing evidence one way or the other.  But in the case of explanations that require us to stretch credulity to the snapping point, I have no problem saying, "Nope.  That one isn't true."

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This week's Skeptophilia book recommendation is an entertaining one -- Bad Astronomy by astronomer and blogger Phil Plait.  Covering everything from Moon landing "hoax" claims to astrology, Plait takes a look at how credulity and wishful thinking have given rise to loony ideas about the universe we live in, and how those ideas simply refuse to die.

Along the way, Plait makes sure to teach some good astronomy, explaining why you can't hear sounds in space, why stars twinkle but planets don't, and how we've used indirect evidence to create a persuasive explanation for how the universe began.  His lucid style is both informative and entertaining, and although you'll sometimes laugh at how goofy the human race can be, you'll come away impressed by how much we've figured out.

[If you purchase the book from Amazon using the image/link below, part of the proceeds goes to supporting Skeptophilia!]

Sunspots and ice ages

If there's one feature of media that drives me the craziest, it's the practice of appending the words "scientists claim" to any damn thing they want to in order to give it unwarranted credibility.

Take, for example, the story that appeared over at RawStory (and also, in similar forms, at The Telegraph and The Daily Mail).  Entitled "'Mini Ice Age' On the Way In 15 Years, Say Scientists," this article takes a piece of legitimate and interesting scientific research and puts a sensationalized spin on it that, if I were one of the researchers, would impel me to write a rebuttal comprised of a single sentence: "I DIDN'T SAY THAT."

First, a little background.  The number of sunspots, which are electromagnetic storms on the surface of the Sun, has been observed to fluctuate on a cycle of about eleven years, but also to be subject to a second (much longer-period) cycle of 370-odd years.  This is the proximal cause of the Maunder Minimum, a time of low sunspot activity that lasted from 1645 to about 1715.

Sunspots in September 2001 [image courtesy of NASA]

Thus far, this probably would merit nothing more than a "So what?" from everyone but astronomy buffs.  Why would popular media even report on something like sunspots?  But the Maunder Minimum, at least in part, coincided with low temperatures in Europe -- the article in RawStory refers (correctly) to the Thames freezing over in winter during that period (although, as you'll see, even that is only one cherry-picked piece of the truth).

So to put it bluntly, the whole purpose of this story is intended to cast doubt on anthropogenic climate change.  "Damn scientists!" you're left thinking.  "Can't even decide if the temperature is rising or falling!"

The problem is, this is a flaw in the media's reporting, not in the science itself.  Let's take this claim apart at the seams, okay?

First, let's look at the basis of the claim -- that the Maunder Minimum predicts extremely cold temperatures.  All it takes is a quick trip to Wikipedia to find out that it's not that simple:

Note that the term "Little Ice Age" applied to the Maunder minimum is something of a misnomer as it implies a period of unremitting cold (and on a global scale), which is not the case.  For example, the coldest winter in the Central England Temperature record is 1683-4, but the winter just 2 years later (both in the middle of the Maunder minimum) was the fifth warmest in the whole 350-year CET record.  Furthermore, summers during the Maunder minimum were not significantly different to those seen in subsequent years.  The drop in global average temperatures in paleoclimate reconstructions at the start of the Little Ice Age was between about 1560 and 1600, whereas the Maunder minimum began almost 50 years later.

If you want to go a little deeper than Wikipedia -- and you should -- check out this cogent and well-written summary of the problem with correlating sunspots and ice ages by Mike Lockwood, professor of space environment physics and a director of research at the University of Reading.  Lockwood writes:

There is very little evidence that the lower global mean temperatures between 1400 and 1800 were caused by solar activity - there's more evidence it was associated with volcanic activity and/or internal oscillations in the climate system...  Much of what has been written in the media and on the internet fails to appreciate the difference between regional and global climates.  My research looks at a potential link between low solar activity and cold European winters. That's a regional and seasonal effect and not a global effect.

If that wasn't unequivocal enough for you, Lockwood goes on to say, "What's more, there's no evidence that summers in the Maunder minimum were any colder than usual.  This is not a 'Little Ice Age' - it is not an ice age of any shape or form."

Second, let's check and see if the scientists cited in the RawStory article actually said anything about an ice age starting in fifteen years.  The lead researcher, Valentina Zharkova of Northumbria University, presented her findings at the National Astronomy Meeting in Llandudno, Wales last week, and a summary appeared in Phys.org.  Here are a few relevant paragraphs:

It is 172 years since a scientist first spotted that the Sun's activity varies over a cycle lasting around 10 to 12 years.  But every cycle is a little different and none of the models of causes to date have fully explained fluctuations.  Many solar physicists have put the cause of the solar cycle down to a dynamo caused by convecting fluid deep within the Sun. Now, Zharkova and her colleagues have found that adding a second dynamo, close to the surface, completes the picture with surprising accuracy. 

"We found magnetic wave components appearing in pairs, originating in two different layers in the Sun's interior.  They both have a frequency of approximately 11 years, although this frequency is slightly different, and they are offset in time.  Over the cycle, the waves fluctuate between the northern and southern hemispheres of the Sun.  Combining both waves together and comparing to real data for the current solar cycle, we found that our predictions showed an accuracy of 97%," said Zharkova... 

Looking ahead to the next solar cycles, the model predicts that the pair of waves become increasingly offset during Cycle 25, which peaks in 2022.  During Cycle 26, which covers the decade from 2030-2040, the two waves will become exactly out of synch and this will cause a significant reduction in solar activity. 

"In cycle 26, the two waves exactly mirror each other – peaking at the same time but in opposite hemispheres of the Sun.  Their interaction will be disruptive, or they will nearly cancel each other.  We predict that this will lead to the properties of a 'Maunder minimum'," said Zharkova.  "Effectively, when the waves are approximately in phase, they can show strong interaction, or resonance, and we have strong solar activity.  When they are out of phase, we have solar minimums.  When there is full phase separation, we have the conditions last seen during the Maunder minimum, 370 years ago."

Is it just me, or did she say nothing about "ice ages?"

But the Maunder Minimum was cold, right?  Couldn't we still see a drop in temperatures if the predicted minimum occurs?  To answer that question, let's go back to Lockwood:

Statistically, we found a significant link between the occurrence of cold winters in the long CET record and solar activity.  By "significant" we mean that there was only a five per cent chance that we were being fooled by a coincidence...  In a paper with scientists from the Met Office's Hadley Centre, we used an energy balance model to show the slowing in anthropogenic global warming associated with decline in solar irradiance to Maunder minimum levels.  We found the likely reduction in warming by 2100 would be between 0.06 and 0.1 degrees Celsius, a very small fraction of the warming we're due to experience as a result of human activity.

Which hits on the central point.  My suspicion is that the hype surrounding the Maunder Minimum and sunspots has one purpose: to reassure us that our activity isn't going to warm the Earth further, and push the climate more out of whack than it already is.  "Don't worry," the media tells us.  "Keep burning your fossil fuels.  The Earth is going to be just fine.  In fact, we might be heading into an ice age!"

And because few people read any deeper than what appears in popular media, they're left with the further impression that the scientists don't know what the hell they're talking about.  We hear about global warming, and then there's an article where "scientists claim" that everything is cooling off.  Is it any wonder that laypeople throw their hands in the air and stop listening?

Which, of course, is what a lot of the powers-that-be want.  Altering the status quo is expensive, and requires unhooking our government from the influence of the fossil fuel industry.  No way can we have that happen.

No way.

Easier to slip into the media misleading stories that subtly cast doubt on the research itself, along with those nasty little words -- "scientists claim."  After that, they can sit back and let natural cynicism and distrust do the rest.