Weathering of Igneous Rocks for Dummies

Two igneous rocks demonstrating different weathering rates

It saddens us here at the Antisocial Network to see stupid answers to simple questions, which is one reason this blog exists. It saddens us even more to see stupid people plying their trade on the internet for money, the other reason this blog exists. When it comes to stupidity, however, we think nothing could be dumber than "answering" a question when you have no idea what it's about. That's precisely what eHow.com's Amanda Rumble did, however, when she accepted the challenge "Why Does Basalt Weather Faster than Granite?" (for some strange reason, moved to Hunker.com; now at Sciencing.com). Of course, her desire to make a fast fifteen smackers had nothing to do with it.

Amanda's lack of knowledge about igneous petrology led her down some strange paths, but if she actually were trained in geology (instead of IT), she would have looked for clues by researching the topic "relative stability of igneous minerals." She could have even found a pretty simple answer here, though then she would have wondered who this Bowen guy was... Instead, her research led her to three different simple sites, NOT ONE OF WHICH addressed her question.

That's why Rumble had to make stuff up. Some of that rubbish includes

The Earth's crust is made up of 3 different kinds of rocks and minerals; sedimentary, metamorphic and igneous - just "rocks," Amanda, not "rocks and minerals." Basalt forms when magma from the ocean surfaces through the crust - "magma from the ocean"? WTF? Granite is the most abundant rock on the Earth's surface - we think she means "in the continental crust." Basalt weathers faster than granite because it is not as hard and it's easier for outside substances to impact and manipulate its structure - there's the bullshit: "impact and manipulate its structure"? WTF does that mean, anyway? Orthoclase has 90-degree cleavage and is pink, white and shades of gray. It contains large amounts of quartz in some areas, making it harder to break, even with cleavage – Orthoclase contains quartz? are you sure? Granite breaks in horizontal planes -  bull, just bull. Basalt is primarily made of the mineral oblivine [sic], which has no cleavage or planes of weakness - no, anorthite is "primarily made of the mineral olivine." Basalt just lacks quartz, idiot! Basalt splits in columns - some of it does, but not all. Idiot.

The answer is simple: minerals are most stable at the their temperature of formation, and granite forms at a lower temperature than basalt. Quartz, an important constituent of granite is very stable at the surface, much more so than any mineral in basalt. To put it simply, basalt weathers faster not because it's softer – nobody gives a rat's hiney about how hard rocks are – but because the minerals found in basalt break down more quickly than those in granite.

Why's that so hard for Rumble to understand? Probably because she didn't know what to look up, and ended up cobbling together a bullshit answer out of general descriptions of igneous rocks. One more reason to ignore the bullshit answers at eHow, where just about everyone eventually ends up as a Dumbass of the Day!

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