Tectonic Plates for Dummies

Oceanic and continental plate comparison

Our staffers have a wide variety of interests, although we admit that most are science geeks or DIYers. To our science geeks, some of the most basic concepts of their fields are ingrained at a near-instinctive level. As a consequence, reading through freelance rubbish that violates those basic principles grates on their nerves, a sure-fire route to a nomination for DotD. Our geology type ran across a Sciencing.com post written by Doug Bennett, "Difference Between Continental & Oceanic Plates," and immediately submitted her nomination...

In straightforward language, the key differences between the continental and oceanic types of tectonic plates boil down to three points: composition, thickness, and age. Bennett actually managed to cover these points... but he did a lousy job, leaving his post splattered with inaccuracies and misinformation. Here are a few of his more bogus statements:

1. "Earth’s surface is divided into approximately a dozen rigid pieces, comprised of eight major and several minor plates."
2. "Oceanic plates are formed by divergent plate boundaries. These zones [are] where the new oceanic crust is being created. As lava flows from these volcanic ridges, it quickly cools, forming extrusive igneous rock."
3. "Oceanic plates are mafic in nature, comprised of basalt rock."
4. "...continental rock is primarily comprised of aluminum and sodium, plus the minerals feldspar and quartz."

Here, for the benefit of people who want to know facts instead of freelancer-generated dumbassery, is our geologist's rebuttal of those claims:

1. Some geologists say seven, not eight, and there are "many" minor plates.
2. Oceanic crust isn't made by lava, nor is it mostly basalt: it's mostly a complex of sheeted dikes injected into the rift zone with the occasional gabbro pluton included.
3. See previous point (not to mention that "basalt rock" is redundant, Doug).
4. No, continental crust is relatively rich in aluminum and sodium, though far richer in silicon. Neither aluminum nor sodium is abundant in its native form – in fact, it's almost impossible to have native sodium at STP.

That's pretty much what you're gonna get when you ask a mechanic and former military cop write about science; especially when his work is "edited" by a journalism graduate who avoided STEM subjects like the plague. We think both of them qualify for Dumbass of the Day...

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