Sedimentary Rocks for Dummy Physicists - The Freelance Files MMCCLXIV

pretty sedimentary rocks

We forget just where we were when we saw the link; but someone, somewhere cited byjus.com as an "authority" on sedimentary rocks. We couldn't pass that one up, at least not after we'd taken a look at the text of an article simply entitled "Sedimentary Rocks" (and filed under "physics"). A little research showed us that Byju's is a massive Indian online learning company with thousands of employees, which renders is impossible to name the actual author of the content. Consequently, we'll just assign authorship to byju.

The topic is fairly vague, but we're pretty certain the text wasn't written by someone with a deep background in earth science. After all, this is the same outfit that, when defining the three major rock types in a different post, told us that,

"...metamorphic rocks are formed when watery hot fluids are subjected to high heat and pressure."

Uh, yeah: someone apparently forgot that metamorphic rocks are rocks that have changed, not "watery hot fluids"! Be that as it may, we're here to debunk some of the bogosity that runs through the site's "educational" post about sedimentary rocks. So, here goes (it's not an exhaustive list, BTW):

• "Sedimentary rocks are created by accumulating existing rocks or fragments of extinct organisms on the Earth’s surface." – We'd like to think that the "existing rocks" are also fragmental, not to mention that any organisms involved are merely deceased – not (yet) "extinct."
• "The particle that helps in forming the sedimentary rock is called sediment." – Besides the sentence's weird construction, that's only true of clastic sedimentary rocks.
• "Its structure is present in rock beds and under surfaces which help record the paleocurrent and has deposited in the rocks."  – Our staff sedimentologist can decode that bushwa (just barely), but an untrained reader would be utterly bamboozled.
• "Organic Sedimentary Rocks: This rock type mainly comprises coal and limestones, which are formed due to the accumulation and deposition of dead plants and animals in rock layers." – Props for knowing the use of "comprise," jeers for that "dead... animals" bullshit. 
• "Chemical Sedimentary Rocks: This type of rock is created when minerals that are present in rock forms undergo a chemical reaction that causes them to cool as precipitates over time before changing back to rock form." – WTF? That's a half-baked mashup of the formation of metamorphic and chemical sedimentary rocks. Simply put, all chemical sedimentary rocks precipitate from seawater.
• "Quartz is a type of sedimentary rock which is used to make glass." – No, folks, quartz is a mineral, not a rock. Quartz-rich sandstone is used to make glass, hence Byju's confusion.
• "Deep sediment burial causes sediment to get compressed and cemented..." – Cementation is not caused by "Deep sediment burial"; cementation requires precipitation from fluids in the pore spaces.

Enough of that; our collective head hurts! We'll leave you with one final assertion as we're on our way out the door to crown today's Dumbass of the Day:

"It helps to know what sedimentary rocks look like if you’re seeking to identify them."

Uhhh, yeah. And it helps to know what bullshit looks like if you're seeking to identify it. In this case, it wasn't particularly hard.

SI - SEDIMENTOLOGY