Today is Veteran’s Day in the United States, a day in which we thank all members of our armed forces, past, present, and future, living or deceased, for their service in protecting our nation and keeping it strong.
I could write a kitchy post about how thankful I am (and I am, believe me. My father retired a full-bird Colonel from the United States Army), but instead I though I’d write about how the science of geology has benefited from the needs of the military.
One of the most fundamental concepts in geology is the Theory of Plate Tectonics. This is how we understand the Earth’s continents to move, and can explain many, many geological phenomena like the abundance of volcanoes around the Pacific Ocean. Plate Tectonics helps us understand why the huge earthquake in Japan in 2012 caused its massive tsunami, and why an earthquake of similar magnitude in California would likely not produce a tsunami. Plate Tectonics helps us understand why and how the volcanoes that make up Hawaii are different from those that make up the the Cascades in the northwestern United States. Plate Tectonics also helps us understand why Africa and South America seem to fit together like pieces in a puzzle.
In the 1912 Alfred Wegener put forward his idea of Continental Drift. He had noted that Africa and South America fitted well together, as well as many of the other continents. He proposed that all the continents were once together, and had subsequently moved apart. The problem with Wegner’s theory was that no one liked the mechanism that he proposed for this. He envisioned the continents plowing across the sea floor from one place to another. This is hard for anyone to imagine, so the theory got panned.
Still, the fit of the continents is pretty darn obvious. No one could understand how the continents could move. Scientists scratched their collective heads and went on with other studies. Until…
During and after World War II, there was a great deal of interest in detecting submarines, as this was the time of the emergence of the cold war and nuclear weaponry. There was a great deal of concern about submarines sneaking up on unsuspecting nations and wreaking havoc. In the 1950’s, scientists began using magnetic instruments towed behind ships to find submarines in the Atlantic Ocean. Whether or not many submarines were found is unclear (and probably classified), but they did find something else quite remarkable.
These stripes were symmetrical around long deep sea mountain ranges called ridges or rises, and provided for the first time a credible mechanism for Plate Tectonics.
The magnetization of the rocks in the stripes were either pointing directly toward the modern north magnetic pole, or in the exact opposite way. This was due to volcanic rocks, as they formed, capturing the Earth’s magnetic field. The magnetic field of the Earth is known to have reversed many times over Earth’s entire history, where sometimes, the north end of a compass needle would point toward the north pole, and at other times the needle would point to the south pole.
If continents were pushed apart by volcanic eruptions and the formation of new crust at the mid-ocean ridges, it would be expected that there would be magnetic stripes forming symmetrically around these ridges. And here they were! This idea, called the Vine-Matthews-Morley hypothesis, provided proof of a viable mechanism for continents to move: that they would be shoved apart by spreading at mid-ocean ridges.
This, combined with the recognition of deep ocean trenches where ocean crust would then be consumed, finally provided an explanation for how continents could move, paving the way toward our modern Theory of Plate Tectonics.
All because we wanted to know where the submarines were.
If you want to read more about Plate Tectonics, and how that relates to earthquakes and volcanoes, please see my post here.