The theory of plate tectonics was always one of my favorite things to teach. Partly because of the way it illustrates principles of the nature of science that I was trying to instill in my students (How a theory unifies many tested hypotheses, how some hypotheses can’t be tested in a laboratory) and partly because I just love rocks. So as well as I thought I knew the topic, I was amazed to come across this tweet Thursday.
A brief tutorial
I am ashamed to say that I had never heard of Marie Tharp. Harry Hess is credited in the textbooks with coming up with the seafloor spreading hypothesis a decade later, but clearly the work of Tharp and Heezen helped lay the groundwork.
Seeing Is Believing: How Marie Tharp Changed Geology Forever
As the tweet says, Marie Tharp was not allowed to go on the research vessels. Instead she stayed at a desk, collaborating with geologist Bruce Heezen. For years Heezen collected the data and Tharp performed the calculations and charted them, plotting her measurements by hand.
Then, something unexpected showed up on Tharp’s canvas: a huge valley in the middle of the gigantic ocean ridge she was mapping. It was so deep that she kept re-checking her calculations. If it was what she thought it was, she would have evidence of a rift valley inside a ridge at the bottom of the North Atlantic Ocean. That, in turn, would be evidence that the huge chain of mountains she was mapping was a place where the oceanic crust was spreading apart.
In her own words:
Not too many people can say this about their lives: The whole world was spread out before me (or at least, the 70 percent of it covered by oceans). I had a blank canvas to fill with extraordinary possibilities, a fascinating jigsaw puzzle to piece together: mapping the world’s vast hidden seafloor. It was a once-in-a-lifetime—a once-in-the-history-of-the-world—opportunity for anyone, but especially for a woman in the 1940s. The nature of the times, the state of the science, and events large and small, logical and illogical, combined to make it all happen.
Her eureka moment:
But I thought the rift valley was real and kept looking for it in all the data I could get. If there were such a thing as continental drift, it seemed logical that something like a mid-ocean rift valley might be involved. The valley would form where new material came up from deep inside the Earth, splitting the mid-ocean ridge in two and pushing the sides apart.
She didn’t get the credit she deserved. I’m glad someone is trying to rectify that on Twitter at least. She doesn’t seem to have cared that much for fame.
I worked in the background for most of my career as a scientist, but I have absolutely no resentments. I thought I was lucky to have a job that was so interesting. Establishing the rift valley and the mid-ocean ridge that went all the way around the world for 40,000 miles—that was something important. You could only do that once. You can’t find anything bigger than that, at least on this planet.
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The full trailer for the documentary short “I Am Rebecca” was released on International Women’s Day.
It’s also been entered at Cannes.