Plants, Stone, California Landscapes


The Devil’s Postpile and Patio

Devils Postpile National Monument

Devil's Postpile National Monument

Probably the most striking geological feature on the eastside, an area full of geological features, is the Devil’s Postpile, one of the world’s best examples of columnar basalt. Columnar basalt is one of those natural elements that looks unnaturally geometric. It forms when it lava cools very, very slowly and evenly. The lava starts to contract and then crack, and because it cools so evenly the cracks form into hexagons, the most stable and efficient shape. As the Park Service page about the formation of the Postpile explains, “a hexagonal system provides the greatest relief with the fewest cracks.” (Bees use the same hexagonal system in their honeycombs because it forms a matrix with the largest amount of storage space for the least amount of wall.) Devil’s Postpile isn’t the only place where this has happened — the Wikipedia entry has links to many other columnar basalt cliffs, and pieces of columnar basalt regularly show up at stoneyards in the Bay Area –but the columns at the Devil’s Postpile are especially long and regular.

The Devils Talus

The Devil's Talus

The base of the cliff has the world’s coolest talus in my opinion. My crew was so well trained/indoctrinated that their first comment was how great these pieces would be for building steps. The park service doesn’t even let you climb on the talus, though, let alone build with it.

The Devils Patio

The Devil's Patio

Possibly the best part is that a glaciar carved off the top and made a natural patio.

The Devils paver pattern

The Devil's Paver Pattern

It’s uncanny how much they look like rough-cut natural stone pavers. Hexagons are stable because three joints come together at every vertex, making for a nice oblique 120 degree angle. The park service says that at Devil’s Postpile 55% of the pieces have 6 sides, 37% have 5, 5% have 7, and the remaining 3% have 4 sides or fewer. That’s a high percentage of hexagons compared to other sites in the world.

the Devils grading

The Devil's Grading

The grading is a bit extreme on parts of the patio.

Surprisingly Comfortable

Surprisingly Comfortable

Ahhh, nice, soft basalt. My crew never saw a flat surface that couldn’t be slept on.

Devils Postpile National Monument

Devil's Postpile National Monument

The columns are shorter and more irregular at the edges where cooling happened more quickly. I don’t know what caused the sinuousness.

basalt columns

Basalt Columns

patinaed basalt

Patinaed Basalt

Devils Postpile National Monument

Patinaed Basalt Cliff

A lot of these ones at the edges are pentagons or squares.

patinaed basalt with Holodiscus microphyllus

Patinaed Basalt with Holodiscus microphyllus

God’s Patio? Granite Slab at Thousand Island Lake

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11 Responses to “The Devil’s Postpile and Patio”

  1. September 11th, 2009 at 8:26 am

    how it grows says:

    Interesting place!

  2. September 12th, 2009 at 8:45 pm

    Town Mouse says:

    That is amazing! I learned about basalt as a kid in school, but they never showed us pictures. These pictures really show how off this amazing stone.

  3. September 13th, 2009 at 4:30 pm

    ryan says:

    Very interesting place, very amazing stone. It’s a great spot.

  4. September 14th, 2009 at 11:19 am

    Pomona Belvedere says:

    Very cool pictures! I was recently introduced to this form of basalt on Steve Snedeker’s blog (the man is an encyclopedia of stone). He found a stash that was available for working with, you might be interested to see what he did. You’re making me want to see this columnar basalt in its native habitat.

  5. September 14th, 2009 at 6:09 pm

    lostlandscape(James) says:

    I was struck by the patio effect myself on one of my last trips through there. I suspect approximating the effect with 5, 6 and 7 sided stone might be a bit of a challenge, though!

  6. September 14th, 2009 at 6:50 pm

    ryan says:

    Yeah, the devil had a good stoneworker for the patio.
    I checked out that post about the basalt project. Very cool. That columnar basalt is surprisingly common in the stoneyards. We installed one as a focal point stone a couple of years ago. The Postpile is worth a visit, especially during wildflower time.

  7. October 12th, 2009 at 8:22 pm

    Pam/Digging says:

    Fascinating! I’d love to see this in person someday. Is this the same kind of formation as the Devil’s Tower in Wyoming?

    Thanks for sending your links to participate in the bloggers’ national park celebration. I’m off to read your others.

  8. October 12th, 2009 at 9:42 pm

    ryan says:

    Yeah, they’re both columnar basalt, though I think people who take their geology really seriously might say that they’re different. Different effect. I saw Devil’s Tower ten years ago, and I want to go back some time and climb it. They allow climbing on it, unlike Devil’s Postpile.

  9. October 15th, 2009 at 8:16 am

    Linda/patchwork says:

    This is fascinating. I never heard of this place. Thanks for sharing with us.

  10. October 18th, 2009 at 5:31 am

    Digging » Bloggers’ Celebration of National Parks: A wrap-up says:

    […] Postpile National Monument, California Ryan of DryStoneGarden shows us the fascinating rock formations at Devils Postpile and the wildflowers at Agnew […]

  11. October 17th, 2010 at 9:34 pm

    DryStoneGarden » Blog Archive » Smith Rock says:

    […] from the main rock groups. The basalt is not as tall or regular as the cliff I posted about at Devil’s Postpile National Monument, but you’re allowed to climb the columns at Smith, unlike at Devil’s Postpile. I was […]

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