Geology 101: Deep Time, or Geologists as Time Lords


He works in a bowtie... (image from

And so do we (well most of us anyways)…

West Virginia Geologists from 1897 (Image from USGS)





(adapted from Steven Marshak’s  Essentials of Geology, 2009.)

A classic example of these principles is the Grand Canyon:









9 thoughts on “Geology 101: Deep Time, or Geologists as Time Lords

  1. Pingback: Doctor Who + Geology = WIN! | En Tequila Es Verdad

  2. Great post! Correct me if I’m wrong (it has been a couple decades since I took chemistry) but I don’t think it’s having an equal number of protons and neutrons that makes an isotope stable. Your example of lead-206 would be 82 protons and 124 neutrons, which would make it pretty unstable by that definition. Or did I misunderstand what you were getting at?

    • You’re correct on all points. For this post I opted to simplify the meaning of an isotope (an atom with a different amount of neutrons compared to its protons) in order to keep the post from getting convoluted. The concept of isotopes and radiometric dating can get rather beastly which is what I was trying to avoid in something aimed at people with no background in the sciences or geology.

      Thank you for the feedback!


  4. Here’s a great explanation from Charles Carrigan at about the actual definition of an isotope:

    To really understand the term isotope, you’ve got to first know the term nuclide – a nuclide refers to an atom with a specific number of protons and a specific number of neutrons. So all the atoms in the universe with 6 protons and 6 neutrons are all carbon-12 nuclides. The number of protons (Z) determines the element, and the number of protons (Z) + neutrons (N) determines the mass of the nuclide (mass often referred to as A = Z + N). It’s a good idea at this point to google “chart of the nuclides” and mess around with what you find there – a chart of nuclides plots Z vs. N. The term “isotope” means “same place”, and it is a reference to the fact that there are multiple nuclides that occupy the same place on the periodic table – i.e., 12C, 13C, and 14C are different nuclides, but all three occupy the same space on the periodic table because they are all carbon, Z = 6. So 12C, 13C, and 14C are isotopes, “same place-rs”. It really isn’t even appropriate to call just 12C an isotope in the singular sense, because the term isotope really means that you are comparing multiple nuclides to each other, and if they occupy the same place on the periodic table, then they are isotopes. So you can have isotopes, but technically you can’t really have an individual isotope. But in common usage people, do often refer to an individual nuclide as “an isotope”.

    Thanks Charles!

  5. Pingback: I Will Hold On to Life Like Grim Death… No, Wait, That’s a Horrible Metaphor | En Tequila Es Verdad

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