Monday, April 29, 2019

Transform Boundaries, the Dummy Version

Transpression (restraining bend) at bend of transform boundary
Transpression at bend of transform boundary
We have to admit it: our collective heart goes pitty-pat when we run across some freelancing "generalist" attempting to discuss some of the more esoteric points of science; especially when said generalist has zero background in the science. Typically, the freelancers know no more (and sometimes less) than the person asking the question they are pretending to answer. That's what happened today, when we caught Doug Bennett of Sciencing.com trying to answer the question, "What Landforms Are Formed at a Transform Boundary?"

What may be most bizarre about this post (besides Bennett's version of the science) is that it's a rewrite of an earlier version written by... wait for it... Doug Bennett. Yup: Bennett rewrote his own post. Did he improve it? Not really, since he did little more than rehash what he'd said before and move things around. It was those "things" that caught our staffer's eye, however.
You see, although convergent boundaries usually result in linear mountain chains, often with volcanoes; and divergent boundaries are often marked by a linear trough lined on both sides by mountain ranges (and lots of volcanism), transform boundaries are relatively boring – when it comes to landforms, that is. Because transform boundaries aren't very "showy," Bennett found himself having to reach a little:
"Linear valleys, small ponds, stream beds split in half, deep trenches, and scarps and ridges often mark the location of a transform boundary..."
...No Doug, those mark the location of a strike-slip fault; except maybe the "stream beds split in half": WTF does that even mean? And "deep" trenches? are you confusing that with a subduction  zone?  Doug then decided that, because he had nothing to say, he'd rattle off 274 words about plate tectonics in general, including this rather confusing statement:
"[The] San Andreas fault... connects the East Pacific Rise, a divergent zone to the south, with the South Gorda, Juan de Fuca plate, a smaller, older plate consisting of all three boundary types and Explorer Ridge, to the north."
Well, our staff geologist is pretty sure he knows what Bennett was trying to say, but it's a safe bet Doug didn't. After conflating transform boundaries with the transform faults that offset segments of spreading centers, Bennett finally gets around to discussing landforms:
"The Dead Sea Rift represents the combination of a rift with a transform boundary. The rift itself, a continuation of the African Rift, forms the valley through which the Jordan River flows. However, this rift is also the location of a transform boundary, where the Arabian Plate is sliding past the Sinai-Israeli Plate.

In this case, both plates are moving northward, but at different rates. This has created a strike-slip fault similar to the San Andreas Fault."
Ummm, Dude? Both plates are moving the same direction along the San Andreas Fault, too... But why is there a rift that is "also the location of a transform boundary"? That's where Bennett missed the boat in his post. You see, wherever there are bends in a transform boundary, the two plates can pull apart ("transtensional") or push together ("transpressional"), depending on the direction of the bend. Doug missed the point: if he had understood this relationship, he might have pointed out that the Transverse Ranges of California are transpressional features.

But he didn't, hence Bennett's Dumbass of the Day award (Doug's second for tectonic buffoonery).
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SI - TECTONICS

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