Fractures for Earth Science Dummies

tensile stress vs. compressive stress

"Once more into the breach," the saying goes. Our staffers with an earth-science bent are constantly amazed (although rarely amused) by the cluelessness of freelancers who think that geology is an "easy" science in comparison to, say, physics or chemistry. You know, the Sheldon Cooper opinion... Whatever the case, it's not so simple that the average freelancer can just reword something and get it right. A case in point is Andrea Becker and her Sciencing.com post, "What Is a Fracture on Earth?" It just goes to show you that a MS in wildlife management probably won't teach you any structural geology...

The reality of Becker's post is that it's little more than a reiteration of what she understood (and in some cases misunderstood) from the Wikipedia entry for fractures. Oh, she cited a bunch of references that mentioned fractures, references she pretended to use, but we know where she got it...
Andrea started out kinda in the middle, by blathering about big earthquakes before moving on the joints and plate boundaries. She immediately cited the New Madrid, Missouri, earthquake of 1812. Why? because she couldn't think of any other faults? The dim bulb claimed to be living in western Washington, in or near the Cascade Mountains, and she had to invoke a Missouri earthquake? What-EVER.

Never mind the rubbish introduction; our staffer tagged this one for DotD mostly because of Becker's lack of attention to detail. We're talking statements such as,

• "A tensile fracture occurs when the edges pull apart as pressure is applied." – Actually, when tension is applied: the rock body is being stretched; pulled in opposite directions. 
• "Extrusive rocks form from magma cooled slowly deep within the Earth." – Sorry, no: those are intrusive rocks, Andrea.

• "To visualize [tensile fracturing], imagine holding a cracker on the edges and snapping it in half." – Ummm, no, that's not the type of stress that results in tensile fracturing; not to mention that such a stress field is highly unlikely (if not impossible) in the natural world. 
• "[The] gaps between the plates are the largest fractures on Earth, and they control the form and movements of the continents." – First off, there are no "gaps" between tectonic plates. Second, the plate boundaries do not "control... the movements of the continents." The movement of the continents controls the type of boundaries where plates abut one another.

So many words, so little correct information. Is it any wonder Becker is our Dumbass of the Day? Of course it's not!

copyright © 2020-2023 scmrak

SI - GEOLOGY