Tuesday, April 10, 2012

Rock Work 101: Part I

The first hand carved rock formation on the TMMC, McKennon Arch
My Thunder Mesa Mining Company may be only 18 square feet but a large portion of that space will be covered entirely with hand-sculpted rock work. There are many tried and true techniques for making rocks for model railroads and most of them involve using molds and heavy plaster. While that might work fine for modeling Pennsylvania shale or  Rocky Mountain cliff faces, it's really not the best way to depict the spectacular buttes, arches, hoodoos and mesas of Southwestern Canyon Country. These unique, stand alone formations call for a different set of techniques and in the next few posts I'll be detailing how I go about creating them.

Modeling Geology

First off, what we're really modeling here is a specific type of geology - not just random "rocks." One thing that makes the artificial rocks at Disney parks so convincing is the Imagineers basic understanding of the geologic features required for place-making in their story. In the case of the Big Thunder attractions Tony Baxter and his team did a great deal of research into places like Monument Valley and Bryce Canyon to make their make-believe formations look and feel believable.

Bryce Canyon National Park, UT

Big Thunder Mountain, Disneyland, CA.
See the resemblance?
While the buttes and hoodoos of Big Thunder at Disneyland reflect a strong Bryce Canyon influence, the Walt Disney World, Paris, and Tokyo versions, while slightly different from each other, all have more of a Monument Valley flavor.

Monument Valley, AZ-UT

Walt Disney World Magic Kingdom

Tokyo Disneyland

Disneyland Paris
What they all have in common is an attempt to artistically recreate the eroded layers of sedimentary rock that are so emblematic of the American Southwest. This region has been alternately inundated by inland seas and windblown sand over the eons, leaving behind the remarkable, colorful layers of sandstone, limestone and shale that have been exposed and sculpted by erosion. Erosion, by the way, is nothing but a fancy word for weather and a whole lot of time. To model these rocks convincingly then, one must attempt to imitate the effects of erosion on layers of sedimentary rock. But which rocks?

Going Back to the Source

While I could just attempt to recreate what exists in the parks, I find it more fun and interesting to do a little "imagineering" of my own and try to design things with the same sort of process that WDI uses. That means going back to the original sources of inspiration and building from there. Personally, my favorite formations in the southwest are located in and around Arches National Park near Moab, Utah, an area in which I've spent a lot of time and know fairly well. 

Park Avenue, Arches National Park

The Organ, Arches National Park

Delicate Arch, Arches National Park
Doesn't get much more spectacular than that does it? The only thing missing is a train ride!

So, now, with the geology of a specific region chosen the job of recreating it in miniature can really begin. The Moab area has several thick layers of red sandstone known collectively as the Entrada formation. These layers erode into fanciful fins, balancing rocks, arches and bridges. Just below the Entrada is the lumpy, limestone Carmel formation which often resembles stacked blocks of stone and forms pedestals for the balanced rocks and hoodoos above. Below the Carmel formation is the cream colored Navajo Sandstone, a dome forming layer which is actually the petrified remains of an ancient blowing sand desert. Understanding where these layers are in relation to each other and how they characteristically erode brings a unified design to the entire model and a certain believability that just randomly placing rocks could never duplicate.

Building a Butte

Baxter's Butte (so far) on the TMMC.

I like the fact that each of the parks has its own unique version of Big Thunder Mountain. My goal for the TMMC is to design and build yet another version; something with a strong "family resemblance" to what's at the parks while still being a little different. With that in mind I went to work, sculpting in polyurethane foam. Right away I deviated from my chosen geology and added in an extra layer of rock about halfway up Baxter's Butte (aka Big Thunder Mt.) Oh, well, it's an artist's prerogative to tweak nature here and there until things look right! Right now things are looking a little too flat to my eyes and I'm not at all sure about the natural bridge and might just lose it. One nice thing about working in foam is that it is very easy to make changes.

I'll go into the details of how I construct and carve these rocks, including the tools and materials used, in my next post in this series. Stay tuned!

Click here for part II of this series.
Click here for part III of this series.


  1. Can anyone learn to carve rocks like that? Did you learn how to sculpt rocks or did you just practice with balsa foam?

  2. I think just about anyone could learn how to do it. Balsa-foam is very easy to work with and very forgiving, if you mess something up you can just scrape it or sand it off. The one thing it does require is good observational skills; you have to look at a lot of real rocks and have some basic understanding of why sedimentary layers look the way they do. When in doubt, copy from photos. The tricky part is making things look random and natural. The human eye craves order and the tendency when carving is too make lines and facets too parellel and straight - you've just got to mix things up. I'd recommend getting some Balsa-foam and experimenting. I had used it before I did this project, but this was my first time making something on this scale with it.


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