Friday Rock Blogging: Sand Boils

a miniature volcano made of sand So sand is just little weensy rocks, anyway. And this is a weensy volcano made of sand, in Peru. It’s about a meter (0.33% of a football field) across.

Normally, layers of sand and silt and crap underground bear the weight of whatever’s on top of them through a network of contacts between individual sand grains. During an earthquake, if the sand grains are loosely packed, this network is disrupted. But the stuff on top is still there, being all heavy and shit. Wacky hijinks ensue!

If the jiggling sand happens to be wet, all the overburden pressure is transferred to the water. Water, being incompressible, is not happy about being squeezed like this; if it finds a suitable weak spot, it will squirt out. And voilà, a pretty sand boil!


  1. denisdekat wrote:

    oh yeah, you did sand So fun!

  2. Joe wrote:

    Sand boils are sweet.
    any geologic phemonena that is described with disease-like terminology is perfect.
    what about:
    limestone warts?
    festering spatter cone?
    infectious sedimentation?
    flatulent fumerole?

  3. yami wrote:

    I’ve always thought “oolitic” sounded rather unhealthy.

  4. Friday Rock Blogging: Evaporites wrote:

    […] known as “squiggly lamination” (”convolute” if you’re trying to sound professional). Like sand boils, it’s formed by squirts of water; unlike sand boils, the formative […]

  5. nikla wrote:

    sand boils turn me on they look cool

  6. Kyle wrote:

    You guys are a bunch of nerds talking about gay sand boils get a fricken life!!

  7. yami wrote:

    Oh man Kyle you have us so pegged. But sometimes we also talk about heterosexual sand boils. And also, it’s not polite to “out” a gay sand boil – even if these two sand boils seem very open about their relationship, they may not feel ready for their grandmothers to know. Now it’s all over the Internet!

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