The Earth's Layers for Dummy Earth Science Students

Layering of the Earth

When it comes to writing about science, it sure looks like the overwhelming majority of would-be "professional writers" arrive at the scene with only the bare minimum of background knowledge. So many of them seem to have chosen college majors that prepared them for reviewing movies or writing literary criticism, but when it comes to scientific facts? Nope... One such "professional," here to dip her toe into science again, is Sciencing.com's Andrea Helaine. We caught her holding forth on the question, "As You Go Deeper Into the Earth What Happens to the Density of the Layers?"

Like so many scientific questions, the answer to this one depends on who's asking: if it's a fourth-grader taking her first earth science class, then Helaine's approach is probably on-target (though her prose isn't). If it's a college student studying seismic exploration, Andrea's answer is pure-D stupid. Even if it's the fourth-grader, though, Helaine should have at least alluded to the more complex answer. On the other hand, what can you expect from someone who opens this discussion by paraphrasing the USGS,

"...Isaac Newton concluded that the Earth’s interior must be composed of a dense material. Newton’s based this conclusion on his studies of planets and the force of gravity. Although much has changed in scientific thought, Newton’s theories about density remain relatively unchanged."

That's not actually what they said, Andrea: they said that "his estimate of the density remains essentially unchanged." That's because his calculation of the Earth's gravitational constant was pretty darned close. That's not what a theory is, however... Anyway, we're here to cut the legs out from under Andrea's pseudoscience, so let's have at it. Here are some of her more cockamamie ideas:

"...the mantle, the outer core, and the inner core. They all have different densities and makeups depending on their proximity to the core..." "Studies of earthquakes — and their waves... inform today’s conclusions" "The upper mantle is made of olivine, pyroxene, and other crystalline minerals, while the lower mantle consists of silicon, magnesium, oxygen — it probably contains iron and other elements." "Liquid in nature, the Earth's outer core is composed of sulfur, oxygen, iron and nickel alloy."

Comments, anyone? Sure, we've got some:

1. What's this bull about "proximity to the core"? The layers Andrea mentions are, in part defined by their "proximity to the core."
2. How else would you study earthquakes, except by their (seismic) waves? Interview them? 
3. Umm, Andrea, your reference says, "The lower mantle... is made up of relatively simple iron and magnesium silicate minerals." That's not the same as "silicon, magnesium, oxygen"!
4. An alloy is a solid, ergo, it can't be "Liquid in nature."

Helaine neglects to mention how we first determined the composition of the solid core [hint: nickel-iron meteorites] and botches any discussion of chemical composition. That's not to mention that she completely glosses over the general increase in density with depth as a result of compression.

This is pretty much the kind of "answer" we'd expect from a Dumbass of the Day, and it's precisely what we got.

copyright © 2019-2021 scmrak

DD - GEOPHYSICS