Tag: ask a geologist

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[Ask a Geologist] Huge Tracts of Land

This should probably be more appropriately titled “Ask a Lady Geologist” but we all know I hate that term. But this is also not about the geology so much as the real estate.

You know, boobs.

Okay, so a dear friend of mine mentioned a descriptive phrase for body position oft-used in our genre: “She crossed her arms under her breasts,” and questioned the mechanics of it. And also why this needs to be described at all, which I think is a fair question because a lot of times it ends up being empty words that just break up a string of dialog, and at most serves as a tacit HEY THIS CHARACTER HAS BOOBS AND IS NOW PUSHING THEM UP SLIGHTLY WITH HER ARMS FOR YOUR VIEWING PLEASURE, HETEROSEXUAL MALE READER.

So yeah. And for some reason this just amused me enough that I wanted to write an entire blog post about it, so there you go.

First off, mechanics: do we breast-bearing people (who need not actually be “ladies,” by the by) cross our arms under our boobs or not?

The answer is, as is often the case: well, it depends.

Personally, I do the underboob arm cross most of the time. But that’s because on the relative scale of breast real estate, I’m somewhere between townhouse and single-family one-story ranch-style on a postage stamp. In general, the smaller the breasts, the easier it is to cross your arms under them because there’s just less mass you have to move. So I know people who are much more well-endowed than myself who just do the overboob arm cross because it’s too much trouble. And there is a point where the tracts of land are so expansive that arm crossing at all is just not comfortable. Also, the length of one’s arms relative to boob size are also a major factor, it seems. Shorter arms make the underboob cross much less comfortable too.

(And please, keep in mind that I am not the last authority on this issue, and there will be other experiences.)

There’s another factor to consider: clothing.

Certain clothes basically make the true underboob arm cross impossible. Sports bras, for example, just kind of squash the boobs flat  so the natural arm position goes on top of the boobs. Bodices and corsets make things kind of weird because they move the boobs up and thus provide an excellent shelf conducive to relaxed overboob arm crossing. Also, if you’re wearing an exceptionally well-tailored dress shirt or coat, most of the time that actually makes it uncomfortable to cross your arms that way at all, because women’s clothing has a tendency to pull across the shoulders–particularly if you have broad shoulders like me.

Other types of clothing may encourage or require an underboob arm cross. For example, on the rare occasions I am threatened at gun point to wear a dress at a formal occasion and am compelled to wear a strapless bra, all arm crossing immediately becomes under boob because I’m absolutely terrified that thing will pop off if I put any pressure on top of it. (The underwires, evil things that they are, also have an effect.)

And so on.

Another, potentially even more important factor: attitude and environment.

I’ve observed–and done this myself–women crossing their arms over their breasts as a defensive gesture. It’s a way to very deliberately shield yourself from unwanted looks or touches, or at least indicate that yes, this shit is very unwanted. Very. I personally have the tendency to do the overboob arm cross the more tense or attentive I am, because cheating my arms a bit lower requires a more relaxed posture. And I’ll even admit to once or twice IN MY ENTIRE LIFE doing an underboob arm cross as a subtle indication to a person whom I found attractive that hello I have breasts and wonder if you would possibly be interested in arranging to touch them at a later time. (I have included this final example for completeness, but for goodness sake this is an exception to the general case, not a rule, and you had damn well better keep that in mind.) [ETA at 1102:] On the other hand, a friend of mine has now said that she feels the underboob arm cross is actually a defensive, but not angry gesture, while the overboob is defensive and angry. So there you go. MAKE NO ASSUMPTIONS.

I imagine this is a YMMV for other breast-bearing humans.

So yeah. It’s complicated.

And I think the far more important question is to ask why it’s even really necessary in the narrative to mention this anyway. If it’s empty place holder action, why the fuck are you writing empty place holder action to begin with? (No really, ask yourself that because I have a really bad problem with doing that kind of empty action myself and I need to knock it off.) What is this action accomplishing? How does it add to the story? Does it say anything useful about the character? (And “The character has breasts, by the way” is not really that useful.)

Personal aside: by the by, when I write a female character crossing her arms, invariable she crosses her arms over her chest. Because I don’t considering the state of the breasts that important. Hm.

If the action is actually important to the narrative (eg: “She deliberately crossed her arms over her breasts to hide her cleavage from the creepy gaze of the Nice Guy(tm).”) then I’m all for it. But if all it really accomplishes is indicating that the character has boobs and they are Super Perky, well. Eh. Probably not the kind of book I’d be reading anyway, right?

Please file this next to, by the way people don’t usually “notice” they have breasts and then describe them in detail so it’s a little weird to the point of creepy when your POV character does it mmmkay?

ETA at 1107: And I am now having an interesting discussion with some friends about how certain kinds of body language have become over-simplified short-hand for emotional or mental states particularly in writing, probably influenced by bullshit ‘psychology of body language’ pieces. For example, putting your hands in your pockets supposedly means you’re hiding something–when often it really just means that you wanted to do something with your hands other than just let them dangle awkwardly at your sides. Or maybe your hands are cold. Or you’re trying to talk with your hands less. Or you’re just feeling casual. Or who knows what else.

There is no single meaning for any particular sort of body language. And while I understand the utility of making particular gestures shortcuts for complex emotional or mental states (eg: the way body language is used in Noh theater) there needs to be an understanding that there is a separation from reality if we’ve hit that point. Which I don’t think there is right now. And it’s also a valid question on if you want your character actions to be coded in a highly stylized way–and if what is perhaps useful for certain types of theater (where there is normally no inner monolog to inform us of the realities of a character’s thoughts and feelings) is really something that should be utilized in the written word.

And wow this got all next level all of a sudden.

ETA at 1126: 

Results of completely non-scientific arm position relative to boobs during arm cross data collection:

Underboob: 8

Overboob: 5

Both: 2

Neither: 2

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ask a geologist

[Ask a Geologist] Young coal and petroleum

Andrew asked:

Would a planet terraformed fifteen million years ago have any petroleum or coal reserves? If so, how would the extent of the deposits compare to Earth?

So, in order to get petroleum or coal, you need the following:

  1. Lots of organic matter building up
  2. Heat and pressure via burial
  3. Time

How much time? That’s kind of the question. You need enough time for geologic processes (normally subsidence) to bury the deposits of organic matter deeply enough that they get pressure cooked at around 49-149C, and then those deposits need to stay cooking long enough for the heat and pressure to crack the organic matter into more familiar hydrocarbons.  How long is that going to take precisely? To be honest, we don’t precisely know. Probably hundreds of thousands of years, not counting the sheer time it’s going to take to bury everything deeply enough.

That said, we at least have an idea of a minimum time, just because we can look at the youngest oil and coal deposits in the world, which are Oligocene to Miocene in age–that gives us a range between about 5.3 and 36.6 million years old.

So yes, as long as your terraforming ramped up quickly enough that you had lots of plants and plankton to die and get buried on land and in the ocean, and your planet was tectonically active enough for active burial (and the temperature and pressure curves line up appropriately for burial) you could potentially have petroleum and coal.

There would probably be a lot less in the way of reserves than we have on Earth, just because your production window would be so much shorter than the one we’ve got. On Earth, we’ve had coal deposits forming since the Carboniferous (a ~355 million year window) and petroleum deposits go back even further, into the Proterozoic (a >565 million year formation window). Just how big the difference will be depends also on how much organic matter your new world is pumping out–if you’re having a mini carboniferous for all 15 million of those years, for example, it still won’t be that much in comparison, but it would be more significant than if your world looks like the Permian.

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ask a geologist geology

[Ask a Geologist] Moon Artifacts

Andrew asked:

Given ancient alien artifacts which take the form of giant stone cubes, made roughly fifteen million years ago, on an airless moon, what sort of information about them or their makers could a geologist infer from analyzing them?

All right, off the top of my head:

Age analysis:

  1. How old the rock itself is, via radiometric analysis, looking at zircons, etc. but this only tells you when the rock itself cooled. Which is of questionable use if we’re talking a sedimentary rock, since at best that will tell you the age of the parent rock. If it’s metamorphic, what radiometric analysis would tell you age wise really depends on the degree of metamorphism.
  2. How long the rock has been exposed on the surface. If we’re taking a moon with no atmosphere, then the artifacts could be examined for pitting/scarring caused by micrometeorites. As long as some measurement can be made as to the historical frequency of that sort of impact on the moon in general, then you could do some statistical analysis and get an idea of exposure time.

Why do we care how old the rock is? Well, if it’s a wildly different age from what it’s sitting on, that implies some interesting things. As does knowing how long it’s been sitting out on the surface, since those two numbers might be quite different.

Basic compositional analysis (here I’m assuming igneous or metamorphic rather than sedimentary rocks):

  1. Are there weird, unknown minerals? What about ones that are incredibly rare on Earth but common elsewhere? Particular sorts of minerals (eg Olivine versus quartz) will tell you about the type of melt the rock came from. Some minerals only occur in certain conditions (eg metamorphic minerals like silliminite) while others indicate a particular, very specific set of formation conditions (like diamonds). This is something you’d learn from x-ray diffraction.
  2. Textures will also tell you important things, like how rapidly the rock cooled, etc. Spinifex texture, fit example, tends to be seen in things like komatiites, which have a very specific melt composition and literally no longer form on Earth today. And all this you can do with thin sections. If you have a sedimentary rock, you can learn ridiculous amounts about the formation of the rock with thin sections, such as looking at generations of cement or weathering features.
  3. Even just looking at bulk oxide makeup (via something like xrf analysis) can give you clues about origin and formational conditions. For example, I used XRD analysis of samples from my vertisols to calculate mean annual precipitation during their formation in my master’s thesis. There is a ton of research out there about various sorts of rocks, formation or weathering conditions, and how that relates to their basic chemical makeup.
  4. At the very least you can use this to figure out if the rock is even native to the area. If there’s something really wild about the composition (for example, there are absolutely no impurities in any of the crystals) that could be a hint that the rocks were manufactured in some way rather than formed in natural conditions.

Visual assessment:
Just by looking at it even, there will be clues about how these things were–or weren’t–made. Tool marks? No tool marks? Or if you look microscopically using some sort of pocket scanning electron microscope, what will you see? Crystals cut cleanly in half? Evidence of flash melting, as if these were shaped using some kind of super heated plasma blade? Or were they made in molds, in which case everything would have crystallized perfectly flat against the mold surface? These visual clues might tell you the most about the makers of the artifacts.

This is obviously a non-exhaustive list. I’m sure there’s a million other things a geologist with a different specialization than mine could think to assess. But hopefully this will get you started!

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ask a geologist geology

[Ask a Geologist] Evidence of a Nuclear Winter

Andrew asked:
Given a rough Earth analog that experienced a major nuclear war about 1 Ma, would there be any evidence of in the rocks in modern times?
All right, so I can think of two major potential lines of evidence off the top of my head when it comes to nuclear weapons:
1) Radioactive isotopes: Most of the radioactive isotopes in nuclear fallout are incredibly short lived, with half lives ranging from minutes to hours to days. (None of the common ones seem to have a half life that lasts more than a year.) So the blasted nuclear hellscape probably wouldn’t still be glowing in a million years, from what I’ve read. If nothing else, consider the fact that it’s safe for people to go to Hiroshima, Nagasaki, and the Trinity test site.
On the other hand, nuclear fallout does cause isotopic shifts that can be traced by chemists. For example, there are different calculations you have to do for pre-industrial and pre-nuclear samples in various kinds of radioactive dating (particularly carbon-14) because it’s caused the amounts of various atmospheric isotopes to shift. Strontium-90 levels also changed due to nuclear testing and that change is recorded in teeth, for example. However, 90Sr and 14C are both short-lived enough isotopes that I don’t think they’d be all that useful for the chemists in a million years. Presumably all the isotopes will have decayed away, though maybe there’s some magical chemistry that could be done looking at relative proportions of daughter isotopes. At this point we’re way outside my comfort zone; geochemistry was never my strong suit. But there is potential there, and if you want to go that route I’d suggest finding a geochemist to ask.
2) Sedimentary evidence. Probably more useful, if your future people have some geologists among them. If you had a worldwide nuclear holocaust, you’d end up with mass extinctions, large-scale fires, and presumably the collapse of civilization. So at the very least, your future explorers would find these signs. Paleontologists would see the evidence for mass extinction, and more damning, would potentially find massive boneyards in multiple locations all dating to the same time, that would indicate a single cataclysmic event. You’d also get charcoal layers associated with the extinction from worldwide fires, and occurrences of “nuclear glass” like the “Trinitite” found at the Trinity test site. All those could be geologically dated to the same time, which would be some pretty damning evidence.
Of course, since it’d be evidence preserved in rocks, they’d have to dig for it or find outcrops. But you should find that kind of stuff around. Heck, you could probably even find buried portions of cities (concrete is pretty hardy stuff; it’s already a rock) and maybe some shadows would be preserved on it, things like that. The trappings of civilization don’t necessarily weather away that fast, particularly not if they get buried in ash and sediment.
As a note, you’d see this kind of evidence preserved both on land (anywhere sediment is aggrading rather than eroding) and in the ocean. Ocean sediment cores would probably show some very strange things going on, an abrupt shift in sedimentation followed by a slow recovery.
Andrew later clarified that he was talking about a slushball Earth, with the global ice age touched off by the nuclear holocaust.
Now, I’m not entirely certain that a global nuclear war would set off global glaciation to begin with. I did some reading on the snowball Earth for a grad class, and I didn’t find most of the proposed mechanisms all that convincing other than lesser solar output and/or change in ocean circulation. The worldwide disaster from a nuclear war might throw a lot of particulates in to the air (and we know those will cause cooling) but they’ll fall out of the air fairly quickly, and consequently dirty up your snow.
But anyway. The slushball Earth isn’t something we need to debate here.
Even with global glaciation, you’ll still end up with geological evidence getting deposited in your oceans, even if at a different rate–but it’s something you’d be able to see with, say, a core drilled into ocean sediments. There’s a reason these kinds of corse get used often for paleoclimate research. In the slushball, there’s still open-ish water at the equator, which can allow for some sediment settling (such as say, the big ash layer) and input. Or if suddenly you’ve got what looks like normal sedimentation that has an ash layer than shifts to something odd like banded iron formations, that’s a big glaring clue that something weird and catastrophic happened.
Thoughts from other geologists?
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[Ask a Geologist] When Geologists Get Funky

Andrew asked:

What DOES happen when you get a bunch of geologists drunk?

For ease of answering, I have prepared this handy-dandy flowchart:

drunk geologist flowchart

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ask a geologist geology

[Ask a Geologist] Of Meteorites and Jars

The lovely and cupcake-alicious E. Catherine Tobler had a couple of geology-related questions, which I have simplified because sooper sekrit reasons:

1) Pretend it’s before 1900–how do you test if a piece of jewelry is made from a meteorite?

After trawling around on the internet a bit, the most likely thing I could come up with is just checking if the jewelry is magnetic and then doing a double check with a streak plate… basically, if the piece is attracted to a magnet, that at least indicates it involves naturally magnetic minerals. And then if you scratch it on a ceramic streak plate and it leaves a metallic gray streak, that’d be a pretty good indicator that it’s at least not one of the usual suspects. Magnetite leaves a black streak and hematite leaves a red streak.

The streak test is a pretty old school one for mineral identification, so it would at least indicate that something weird is going on if you have this magnetic thing that’s not leaving an expected streak color. I know there are also chemical tests you can do to see if something contains nickel, which would be a big hint since all metallic meteorites are nickel/iron.

I don’t know precisely when the streak test came into wide use or when they really started cataloging streak color for minerals. But Mohs hardness scale was invented in 1812, and that kind of testing has been in use since basically the Greeks, just not standardized. Streak testing is an outgrowth of hardness testing, since when you rub something on a substance that is harder than it, you leave a streak of powdered mineral behind.

That said, I didn’t quite trust my own answer on this, so I e-mail my planetologist buddy John Dee since he knows space rocks so much better than I do. Here’s what he had to suggest:

Easy-peasy – just cut it in two, etch it with nitric acid and look for the Widmanstätten pattern. The pattern is formed when the iron core of a planetismal slowly cools and creates interlocking crystals. When the planetismal is later broken into pieces, it forms the stoney and iron meteorites.

Magnetism won’t be much use, as the planetismal probably wasn’t large enough to have an intrinsic magnetic field. And the streak pattern won’t be diagnostic because you’ll get the same result for native iron. But only a meteorite will give you the Widmanstätten pattern!

I don’t know if cutting the jewelry in half is actually an option, but even just etching the outside of it should reveal the Widmanstätten pattern. And so long as the jewelry was made without completely melting down the meteorite–if you just heated it enough to get it to bend instead, for example–that would be the best indicator for certain.

Question number two was a little less out of this world:

2) You’re in ancient Egypt. What kind of rock would you use to make a container for a liquid?

I found this awesome site that listed Ancient Egyptian quarries and mines and what each one produced. Which made answering this a lot easier. Basically, the material would need to be workable (well, presumably anything in the above quarries were things the Egyptians knew how to work), would need to be durable, would need to not react with what you put in it, and would need to be non-porous (to prevent seeping or desiccation).

So this eliminated things like schist (flaky), sandstone (potentially porous), and gypsum (too dang soft).

That leaves a lot of good options still:

  • Quartzite would definitely work. A good quartzite will be completely cemented with quartz, so that would take care of the pore space issue. Quartz is also pretty resistant to chemical weathering, so wouldn’t interact with much you’d put in it to the best of my knowledge… it’s a tough mineral. And we know that the Egyptians had access to a quarry with quartzite in it.
  • Travertine and regular limestone (which would potentially be cool looking and fossiliferous) also might work all right since as far as I’ve been able to find, and unless you filled it with acid wouldn’t interact with the liquid. (And as long as you keep them in a dry climate, both of those will last forever and ever.) The big thing again would be to make certain it was non-porous limestone–it just can’t have vugs in it, or a lot of dissolution molds. I think Travertine would likely be good since it’s hydrothermal… though the other thing to keep in mind is that hydrothermal sourced rocks might have some other nasty impurities in them since a lot of metallic and heavy elements tend to get kicked up in hydrothermal systems.
  • Granite or diorite could potentially work too. Since all the crystals are interlocking, it’d make for a water-tight or even air-tight vessel, but it could be a bitch to work and polish up I imagine.
  • The one option I like the best is serpentinite. There’s a quarry for that, and it would make a darn cool looking green or black jar. I also found a reference that said serpentinite was used for small decorative containers, so there you go.

Looking up all that information about quarries was really fun!

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ask a geologist geology geomorph

[Ask a Geologist] Before there was terraforming, there were rocks

My friend Andrew Barton asked me, a bit out of the blue via twitter:

Given a now-earthlike planet terraformed 15 million years ago, which previously resembled an Earth-sized Iapetus or something, how obvious would the pre-terraforming rocks be, or what governs how deep they’d be now?

He also provided a bit more background as to the reason behind the question:

I’m still working out a lot of the details; this involves Esperanza, the terraformed habitable moon of HD 28185 b that was the setting of “The Paragon of Animals” in the March 2013 Analog, and hopefully additional stuff down the line. While tectonically active and geographically varied at present, it was entirely lifeless before the terraforming process began.

I should probably be ashamed to admit it, but I didn’t actually have an idea what Iapetus would be like. And didn’t look it up until this very moment (naughty, naughty) but I don’t think that would have changed the answer I sent him. Which is long and a bit rambling, but I was thinking it through as I went since the question was fairly general.

  1. How deep do the effects of the terraforming go? If it’s just a matter of soil modification/creation, I wouldn’t really expect most bare rock to be all that altered. If it’s a change to atmospheric chemistry that will completely redefine the way weathering works on the planet, that’s a whole different matter. Also, microbial life does have a profound effect on how any rock that’s exposed to air will degrade (we even see this deep in mines/hydrothermal vents) but did the terraforming, say, completely alter the habitats of the extremophiles?
  2. How tectonically active is your planet? If you’re getting regular tectonic activity like you see in modern Earth, there’s a good chance that you would get exposures of relatively pristine rock fairly regularly; if there’s a large earthquake that causes a major landscape drop, you’ll get a fault scarp where new rock will be exposed. These aren’t the most common events, but you’d probably get a bit of that happening during 15 million years. Of course, as soon as you expose the fresh rock face to the surface, it will start being effected by the terraforming.
  3. If you’ve got landscapes with a lot of relief (eg: mountains) then you’ll have an ongoing process of mass wasting (landslides, rockslides, etc) that can expose fresh surfaces.
  4. Weathering rates will determine a lot, but 15 million years isn’t that much time to redefine a landscape, particularly if you’re just changing the air and water chemistry and not effecting the tectonics at all. Erosion rates are generally less than 1mm/yr (but up to 10mm/yr in places like New Zealand and the Himalayas that have high relief, active mountain building, and plenty of moisture) and one thing you have to consider is that as material is being eroded from the surface, it’s not necessarily going to just expose something pristine beneath it… whatever is right beneath it will probably be in some way chemically weathered by the time you get to it, because water ruins everyone’s life.
  5. As far as “how deep” the pre-terraforming rocks would be, it’s basically just going to be anything below the zone where your new bacteria/weather can effect it. Which will vary wildly depending on the environment in question. In the classic case of a single non-stacked soil, you could potentially hit bedrock less than 1.5 meters down… but then that bedrock has been subjected to the presumably terraformed water regime. And how deep that water would go would be determined by things like the type of rock, its porosity, and how fractured it is.
  6. So basically your biggest problem, depending on what exactly the terraforming entailed, is trying to find rocks that have not been touched by air/microbes/water from the new surface.
  7. Probably your best bet if your people are digging would be to get below the water table if you want completely pristine rocks. In the majority of places, the freshwater table will stop at about 30-35 meters below the surface, but it can go as deep as 370 meters or so.
  8. Just as a note, for buried pre-terraforming rocks, what you’ll be looking for are sedimentary rocks. Those are the ones that will give you the clearest picture of surface and near surface conditions at the time of their formation (and early diagenesis). And that would presumably provide a very different environmental picture from what currently exists. (Like gosh there are no fossils of any kind in these older rocks…) The good thing is, those rocks have had the entire existence of the planet to form and be buried, so there ought to be plenty of them lurking just below the surface.

Tl;dr: That’s a really complicated question.

Obviously, I’m not the world’s greatest expert on this topic–any other geologists out there have thoughts? Did I get anything completely wrong? Just drop a note in the comments. I’m sure I didn’t think of everything.