Tearing down the roadblocks

I wonder if you've heard of Marie Tharp.  I hope you have, but suspect you haven't.  Even in scientific circles, her name is not exactly a household word.

It should be.

Back in 1912, a German geologist and climatologist named Alfred Wegener noticed correspondences that seemed too great to be coincidences.  First, there was the thing that just about everyone wonders about in grade school -- the puzzle-piece contours of Europe and Africa with North and South America.  Then there was the fact that the fossil record of those two regions are similar until about two hundred million years ago, and afterward gradually diverge.  And last, he observed that the Appalachian, Pennine, and Scandinavian Mountains are geologically similar and seem to have formed at around the same time.  As you undoubtedly know, Wegener put all that together and proposed that they were all explained by continental drift -- that the land masses were all united at one point, then broke up and drifted apart, splitting what had been a single continent with a contiguous mountain range into widely-separated pieces.

The main reason this wasn't well-received was not only, or even mainly, because of hidebound scientists clinging to old models; it was that Wegener couldn't explain how, or why, it had occurred.  He proposed no mechanism to account for continents "drifting" in what appeared to be solid rock.  So while it's a pity for poor Wegener that he'd landed on the correct answer and got no recognition for it (he died at age fifty in 1930 on an expedition to Greenland, thirty years before plate tectonics was proposed), his theory's poor reception is honestly understandable.

What happened to Marie Tharp in the 1950s is less forgivable.

Tharp was an oceanographer who fell into the profession almost by accident.  She was fascinated with science, but women back then were actively discouraged from pursuing careers in scientific fields; they were frequently given helpful advice like "it's extremely difficult for women to compete as scientists," with few of the (male) advisors and supervisors asking themselves the question of why that was, and more importantly, if maybe, just maybe, it was a problem they should work on fixing.  During World War II, though, when a lot of college-age men were overseas fighting, colleges started actively recruiting -- well, just about anyone, even those from groups that had been previously excluded.  Tharp took a geology class and was fascinated by the subject, so she enrolled in graduate school at the University of Michigan at Ann Arbor, completing a master's degree in petroleum geology in 1944.

After that, though, she ran into the difficulty that geology and related sciences rely on field work, and nearly all of the companies that hired geologists didn't allow women to work in the field.  So Tharp was relegated to analyzing data -- especially mapping data -- that had been collected and brought back by her male colleagues.

Tharp in 1968 [Image is in the Public Domain]

It was when she was working on a project to map the deep parts of the Atlantic she noticed something odd.  For a decade, ships had been crisscrossing the Atlantic Ocean using sounding devices to map the topography of the ocean floor, initially as a way of locating downed aircraft and ships.  But as she was creating contour maps, Tharp found that there was a huge mountain range running all the way down the center, from north to south -- and that mountain range had a narrow, deep, v-shaped valley right down the middle.  Then she started plotting the epicenters of submarine earthquakes onto the map, and found they coincided almost perfectly with the ridge and valley.

As soon as she saw this, she knew Wegener had been right.

The rift, she claimed, was where the motive force arose that was forcing the continents apart.  It was seismically active, and (she rightly predicted) should be characterized by newly-formed igneous rock, as the split between the continents widened and lava from the mantle bubbled up and froze on contact with cold seawater.  She told her supervisor, geologist Bruce Heezen, who promptly laughed at her, characterizing her explanation as "girls' talk."

Tharp, fortunately, was not so easily dissuaded.  She kept at it, and after several years had enough data amassed that the evidence was absolutely incontrovertible.  Even Heezen finally gave in.  Those ridges and valleys were eventually found to be a network of rifts encircling the globe like the stitching on a baseball, and her idea that they were responsible for plate tectonics was absolutely spot-on.  But it's significant that of the many papers about the Mid-Atlantic Ridge and plate tectonics that Heezen and others published in the 1960s and 1970s, Tharp's contributions were acknowledged on exactly zero of them.  The person who was credited with discovering the Mid-Atlantic Rift Zone, and proposing its role in continental drift, was...

... you guessed it...

... Bruce Heezen.

She was eventually recognized for her brilliance and hard work, but like a lot of women scientists, didn't receive it until quite late in her career.  She was awarded the National Geographic Society's Hubbard Medal in 1978, Woods Hole Oceanographic Institute's Mary Sears Woman Pioneer in Oceanography Award in 1999, and the Lamont-Doherty Earth Observatory Heritage Award in 2001, five years before her death at the age of 86.

It's certainly easier for women in science now, in part due to indomitable women like Marie Tharp.  But the fact that it's not equally easy for men and women -- which it still very much isn't -- illustrates that we have a long way to go in welcoming women, minorities, and LGBTQ+ people into every career avenue.  If you're one of those people who has ridiculed DEI (diversity, equity, and inclusion) drives in education, business, and industry, then maybe you should be working harder to create a world where we don't need them any more.

Odd how those who are most vocally against DEI seldom have any cogent arguments why they think it's appropriate or fair to set up roadblocks that result in wasting over half of the potential talent, drive, passion, and genius we have at our fingertips.

Most people who are interested in geology have heard of Wegener, and pioneers like Drummond Matthews, Frederick Vine, and Harry Hess.  Far fewer have heard of Marie Tharp, who overcame tremendous personal and professional hurdles to revolutionize our understanding of how the Earth's geological systems work.

Hearing about her struggles won't undo the unfairness and misogyny she dealt with during her entire professional life, but maybe it will assure that this generation of women scientists don't have to endure the same thing.

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The climatic teeter-totter

Want a take on something familiar that will (probably) turn your mental image of it on its head?

Picture dinosaurs.  Not just the dinosaurs themselves, but where they are -- the terrain, plant life, and so on.  I'm guessing you probably came up with something like this:

[Image licensed under the Creative Commons ABelov2014 (https://abelov2014.deviantart.com/), Wessex Formation dinosaurs, CC BY-SA 3.0]

Lush, steamy, wet, sort of like today's Amazon rainforests.  It's no surprise Jurassic Park was set on a (fictional) island, Isla Nublar, off the coast of Costa Rica.

And we know for certain that part of the "Age of the Dinosaurs" had a lot of these characteristics.  The global climate from the mid-Jurassic to the end of the Cretaceous was largely warm and moist.  But a new study, published last week in Science Advances, suggests that the dinosaurs may have come to prominence not because of their adaptation to warm climates, but because of their resistance to cold ones.

Just about everyone knows about the KT (Cretaceous-Tertiary) Extinction, that wiped out all the non-avian dinosaurs, and is now attributed with near certainty to the impact of the Chicxulub Meteorite sixty-six million years ago.  Most people also have heard about the biggest mass extinction ever, the Permian-Triassic Extinction, that by some estimates wiped out between eighty and ninety percent of life on Earth, 252 million years ago.  Surprisingly few people have heard about the End-Triassic Extinction -- surprising because it caused nearly as much decrease in biodiversity as the Cretaceous-Tertiary Extinction would 135 million years later.

One of the reasons that this event doesn't get much attention is that the wipeout seems to have been gradual rather than sudden and dramatic, as both the Cretaceous-Tertiary and Permian-Triassic Extinction were.  "Gradual," of course, is in human terms; in geological or paleontological terms, it happened pretty damn quickly, over a period of about eight hundred thousand years or so.  The cause isn't as well understood as either of the other aforementioned extinction events, but seems to have been because of a climatic rollercoaster that first cooled the climate dramatically, and then warmed it up even more.  The cause is thought to have been the opening up of the Central Atlantic Magmatic Province, a line of enormous volcanoes that split what had been the supercontinent of Pangaea in half and opened up the Atlantic Ocean.  Eventually the province became the modern Mid-Atlantic Ridge (which is still driving North and South America away from Europe and Africa at a rate of about 2.5 centimeters a year).

The climate had already been cooling during the late Triassic, and sea levels fell as seawater got locked up into polar ice caps and glaciers.  The eruptions of the CAMP initially dropped the temperature even more, favoring cold-adapted animals and plants.  But just as we've seen from modern volcanic eruptions, the "volcanic cold snaps" we get from sunlight-blocking effects of the ash and debris being launched aloft eventually rebound into a warming event because of the pulse of carbon dioxide injected into the atmosphere.

That's what happened here, only on a huge scale.  The climatic teeter-totter tilted first toward significant cold and then into a warm, wet period, and the big winners in both scenarios were the dinosaurs.  We know about their ability to tolerate heat; like I said, mostly that's the kind of environment we picture them living in.  But their ability to weather a cold period seems to have been due to an adaptation their amphibian cousins didn't have: feathers.

We always tend to associate feathers with flight, for the very good reason that birds use them for that purpose.  But what we have here is a great example of preadaptation (sometimes shortened to preaptation), in which a trait evolved in one context gains another, unrelated, function and experiences a whole bunch of different selective pressures.  Feathers, which are modified reptilian scales (look at a snake scale under a microscope and you'll see the similarity), started out as heat-trapping devices; cold-adapted birds like penguins still use them that way.  Once small arboreal dinosaurs began to use feathered limbs as aids to gliding when they jumped from branch to branch, all of a sudden they became seriously well-adapted for something else, and opened the road to modern birds.

The more well-preserved dinosaur fossils we find, the more species we find that had feathers -- including the ones that didn't fly.  Even pterosaurs, which we usually picture as having leathery wings, were apparently covered with something very much like fur or fine down feathers.  (In fact, one of the small pterosaurs of the late Jurassic is called Sordes pilosus, which roughly translates as "hairy devil.")

So the initial temperature drop at the end of the Triassic Period favored dinosaurs with insulation -- then when the temperature rebounded into jungle conditions in the early Jurassic, the competition (in the form of large amphibian species) were mostly extinct, and the dinosaurs really took off, one branch of them using their feathery innovations for something entirely different.  

I always find it wryly funny when people think of dinosaurs as being some kind of "failed experiment" or "evolutionary dead end," when they were actually the dominant life form for 185 million years, which is almost six hundred times longer than modern humans have existed.  In fact, most studies have flatly contradicted the notion that "dinosaurs were already declining and then the meteorite impact finished them off" -- all indications are that they were doing just fine when Chicxulub hit.  Odd to think of it, but if it hadn't been for that catastrophic impact and horrifying extinction, our own ancestors would very likely never have thrived and spread -- and dinosaurs of some form might still be the dominant animal life on Earth.

But as far as the end-Triassic climate yo-yo goes, it just shows that when the external conditions change, what was a disadvantage can suddenly become an advantage, and what was an advantage can become a disadvantage -- or an advantage of another sort.  If things change fast, so can the winners and losers.

In this case, favoring a group that would go on to rule the planet for another 135 million years.

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