Skepticism

Dinosaurs, Volcanoes, and Antarctica, Oh My!

As an undergraduate, I often selected my courses for the next semester somewhat arbitrarily from the course catalog based on the distributive requirements they filled and, most importantly, on their snazzy titles and two-sentence decsriptions. One of the beauties of attending a liberal arts school is that you can take random classes such as “Phallic Symbols in Ancient Greece” or “Hidden Meanings in the Lyrics of Bob Dylan,” and it’s okay. After all, the point of a liberal arts education is to broaden your horizons, not prepare you for a job in the real world.

So, I chose at least three of my college courses based on their titles alone, “Dinosaurs,” “Volcanology,” and “Introduction to the Earth’s Cold Regions.” While these courses provided me with very little information relevent for my daily life, they did at least prepare me to read this great science news article on the well-preserved remains of a baby plesiosaur:

Baby Dino Fossil in Antarctica

Note that this extraordinary fossil was found in a layer of volcanic ash, a point that I think is worth emphasizing. Geology texts generally teach that fossils can only be preserved in cooler, slower-moving sedimentary deposits. However, this isn’t true: igneous or volcanic fossils are common, and they often represent the best-preserved biological or archaeological specimens available.

Fossils formed in volcanic ash deposits have the advantage of essentially preserving a snapshot of time. For instance, there are the fossil remains at Pompeii or Tambora, the so-called Pompeii of the East. Archaeologists can’t beat cities preserved in situ in volcanic ash for investigating daily life (and, I suppose, a moment of panic as people realized they were about to buried…) in an ancient city. I also think that there may be something about silica-rich volcanic ash which chemically aids the fossilization process. Certain types of fossils, such as fossilized bones and petrified trees, are formed when silica replaces organic material. Maybe high-silica ash flows are particularly good at preserving fossils– better than mud and sediment, maybe? I don’t think much research has been done on this topic, but it’s a point worth investigating.

Okay, so it’s clear that there are some neat fossils in relatively cool volcanic ash flows. What about lava flows, though? Forming fossils in very hot (900 degrees C or hotter) lava flows seems unlikely. However, there are even rare cases of this. For instance, molds of tree trunks are sometimes found in lava flows because the water excreted by the trees cools the lava enough so that the a mold of the tree can form before the tree becomes toast from the heat of the lava. In Washington state there is also the famous Blue Lake Rhino. The lava flows formed a mold around a dead, bloated rhino. Again, here water played a key role. The water released by this swollen rhino allowed the lava to cool and form the mold before destroying the rhino.

My bet is that there are many more igneous fossils than archaeologists and geologists realize. Researchers just need to look for them in the right places, in the right ways.

Death by fire, then frozen in time… now, that’s a dramatic way to go. If I’m ever killed on one of my trips to an active volcano, at least maybe I’ll end up as a cool museum fossil a few hundred years from now.

Evelyn

Evelyn is a geologist, writer, traveler, and skeptic residing in Cape Town, South Africa with frequent trips back to the US for work. She has two adorable cats; enjoys hiking, rock climbing, and kayaking; and has a very large rock collection. You can follow her on twitter @GeoEvelyn. She also writes a geology blog called Georneys.

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13 Comments

  1. Since bone is a spongy material on the inside (sort of honeycomb-like), and thus has lots of empty space inside, I can see how outside chemicals (like silica?) migh find their way inside, although technically they wouldn't replace the bone material then, but more likely just fill up the empty space inbetween.

  2. AWESOME post! I went to the UW in Seattle as an undergrad, and I remember visiting the Burke Museum. I must have seen the rhino there but didn't pay any attention to its story. My bad! My dad also took me to Soap Lake once when I was a kid, to let me feel the water in the lake. It's truly "soapy" feeling. Must be fairly basic due to the minerals.

    A very cool post and a trip down memory lane, all in one! Many thanks, Evelyn.

  3. Thanks for the positive feedback, everyone!

    Paleoprof– you're right about permineralization, but wouldn't silica-rich volcanic ash be good for that, too? I'm not an expert on fossilization chemistry, but it seems logical to me. Silica is robust material. Ash is also very good at making molds, such as is the case in many of the Pompeii fossils.

    I'm a big fan of lahars, too… though I wouldn't want to be in the path of one as it comes cascading down a mountainside!

  4. Very cool stuff. I’ve collected exceedingly delicate yet well-preserved Eocene leaves in Texas in a volcanic ash (about the only use I had for igneous rock :) I do think you’re onto something with the felsic ash contributing silica to the preservation process, but I think that with bone and wood the more common mode of preservation is permineralization not replacement although both probably happen.
    If I were looking in a volcanic terrane for fossils I think I’d go for the lahars. (mostly because I like saying lahar)

  5. …. sorry …. thats just hot.

    the girly nerd speak I mean.

    I would guess that lahar’s wouldn’t be too hot but I know dink about them except those I’ve seen on video tape.

    AAAAAAaaaannnnd I’ve just crossed over to creepy internet guy land.

  6. Evelyn

    I'm with you, I'm a big fan of lahars AFTER the fact. If fact that sort of describes my relationship with volcanoes in general.

    I think silica-rich ash would be great at providing silica for permineralization. It's small so chemical weathering should happen quickly and as long as it's not compressed too much or welded I would imagine it's fairly permeable stuff. And since it's igneous you can radiometrically (sp) date it. All in all handy stuff for an igneous rock.

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