Skeptophilia (skep-to-fil-i-a) (n.) - the love of logical thought, skepticism, and thinking critically. Being an exploration of the applications of skeptical thinking to the world at large, with periodic excursions into linguistics, music, politics, cryptozoology, and why people keep seeing the face of Jesus on grilled cheese sandwiches.
Showing posts with label continental drift. Show all posts
Showing posts with label continental drift. Show all posts

Thursday, September 12, 2024

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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Monday, December 9, 2019

The fluid Earth

I've always had a fascination for maps, and when I was a kid spent many happy hours perusing a huge old world atlas my parents owned.

I remember how impossibly exotic a lot of those places seemed.  Some of them, too, seemed awfully oddly-shaped.  I remember being struck, for example, by the peculiar contour of the island of Celebes (now known as Sulawesi):

Map from The Birds of Celebes and the Neighouring Islands (1898) [Image is in the Public Domain]

What on earth gave the place its strange shape?  I was years away from finding out about plate tectonics, seafloor spreading, and continental drift -- this would have been 1968 or so, and the seminal paper by Fred Vine and Drummond Matthews confirming the truth of plate tectonics had only been published five years earlier, so the idea had yet to make its way into elementary school science classes.

The first inkling I had that the current map of the world was only the latest of a myriad configurations that Earth's land masses had taken was when I found out about marine fossils on the top of Mount Everest and tropical fossils in Antarctica in a book I had on prehistoric life.  Everything was shifting around, apparently, in some mysterious fashion, and the familiar maps from my parents' atlas would have been completely incorrect in the past.  For example, India broke off from what is now Madagascar, sliding across the ocean on its piece of plate, and rammed into Asia only fifty or so million years ago -- which may seem like a long time, but at that point the dinosaurs had already been extinct for fifteen million years (as I always feel obliged to add, except for birds).

Still, I didn't know much in the way of details.  When I took two geology courses in graduate school, however, I hit the idea head-on, including the now-familiar idea of Pangaea -- that there was a time when all of the continents were joined into one enormous land mass.  Even more mindblowing was the fact that this wasn't the only time this had happened -- the accretion and disintegration had occurred at least three or four times before, each time ending when rifts formed and forced the place apart.

The traces of these repeated hookups and breakups are still with us.  In fact, one was just announced in a paper recently in Geology, by a team led by Adam Nordsvan of Curtin University, in which evidence was uncovered that a piece of Australia -- the region of Georgetown in far northeastern Queensland -- was actually geologically related not to the rocks immediately adjacent to it, but to rocks in (of all places) Canada.

The Canadian (or Laurentian) Shield is one of the oldest relatively unaltered blocks of rock on the Earth, of Precambrian age -- on the order of three and a half billion years old -- so to a geologist, they're pretty distinct from the geology of the nearby Mount Isa formation, which is only half that old.  (I realize how ridiculous it is to use the word "only" to describe something 1.8 billion years old, but I'm trying to think like a geologist, here.)

The coolest thing is that the piece of Canada left behind in Australia wasn't from the most recent continental pile-up, which occurred on the order of three hundred million years ago, nor even the one before that.  The most likely time that Canada and Australia were joined together was three supercontinents ago, when all the Earth's land masses were fused around a billion years ago into a huge clump called Rodinia:

[Image is in the Public Domain]

So apparently when that rifted apart, around 750 million years ago, a chunk of Canada decided to split off and ended up (literally) on the other side of the world.

The whole thing is pretty cool.  I'm still fascinated by maps in general, and thinking about what the world was like when Antarctica was in the tropics of the Northern Hemisphere and the equator cut across what is now Labrador will never fail to spark my imagination.  Add to that the bizarre thought (to me, at least) that at that point, all living things were confined to the oceans -- there was not a bug, not a worm, not so much as a sprig of moss anywhere on land, the whole place was completely devoid of life -- well, it brings to mind the line from Contact about a universe empty of all life except for us being an "awful waste of space."

Fortunately for us, though, at that point the conquest of dry land was right around the corner.

"Only" three hundred million years later.

I'll end with the prescient lines from Alfred, Lord Tennyson, penned in 1849, long before continental drift was even considered:
There rolls the deep where grew the tree.
O Earth, what changes hast thou seen?
There where the long road roars has been
The stillness of the central sea;
The hills are shadows, and they flow
From form to form, and nothing stands,
They melt like mists, the solid lands,
Like clouds, they shape themselves and go.
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This week's Skeptophilia book of the week is brand new; Brian Clegg's wonderful Dark Matter and Dark Energy: The Hidden 95% of the Universe.  In this book, Clegg outlines "the biggest puzzle science has ever faced" -- the evidence for the substances that provide the majority of the gravitational force holding the nearby universe together, while simultaneously making the universe as a whole fly apart -- and which has (thus far) completely resisted all attempts to ascertain its nature.

Clegg also gives us some of the cutting-edge explanations physicists are now proposing, and the experiments that are being done to test them.  The science is sure to change quickly -- every week we seem to hear about new data providing information on the dark 95% of what's around us -- but if you want the most recently-crafted lens on the subject, this is it.

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