Ask Devin

Past Question Archive 

Shad from Mansfield asks:

How many 14's are there in Colorado?  Geologically speaking, why was the rest of the rocky mountain states robbed of having a 14er in their state and CO ended up with so many? ID-0, MT-0, WY-0, UT-0, NM-0, CO-??

Devin says:

Well Shad, at last check (barring any recent volcanic or tectonic activity I am unaware of) there are a total of 54 mountains in Colorado that currently rise above the 14,000 foot mark (that's asl... above sea level).

Obviously Colorado is not the only state in the US to have 14'ers. California has 'em, as does Alaska and Washington. But you make a great point that one could expect 14'ers in Montana, Wyoming, Utah or New Mexico, as well as Oregon, Hawaii and Idaho...(technically, Mauna Kea in Hawaii is a 29'er from ocean bottom to top, but hey, who's counting.

It's true that the mountains in Colorado are slightly taller, and we can look to their geologic history for an attempt at answers...here's my best educated guess on the subject.

Imagine this...about 70 million years ago, during what is called the Laramide orogeny (orogeny meaning "mountain building episode"), subduction is theorized to have been occurring on the Pacific tectonic plate as it slides up under California and Nevada (unlike today's strike-slip fault style, California was believed then to have been more like Japan or Washington State than the California of today). In what was flat dinosaur-riddled ocean basin prior to this time, the new Rockies began forming, with volcanoes, faults and all the trimmings. Wild times indeed.

As this ocean plate subducted shallowly underneath the western portions of the US, it must have created significant stresses on the deep crustal rocks throughout the western US, probably stirring up the upper mantle pretty good under there to boot. Those blocks of hard basement rock holding up the crust were disturbed by this incursion scraping it's bottom, causing them to break up and bob up and down like blocks of wood or ice floating in a lake. The maximum eastward limits that this stress was exhibited in the area of Colorado, which happens to be the general area of the highest mountains in the lower 48 states. Significant? Oh, Most likely.

Shortly after the initial uplifting of the Rockies, maybe 30 million years later, erosion had pretty much ground these mountains down into bite-sized hills, not worthy of your attention, when another period of mountain building began uplifting these older "Rockies" rocks. Finally, about 5 million years ago, another active period of localized uplift was responsible for the current "altitude" of the Colorado peaks. So really several events over a 65 million year period are collectively responsible for the landscapes we see today.

Like a car crash where the Civic runs up under a Diesel truck, the plate (the Civic) pushed these layers of deep, hard intrusive igneous, sedimentary and metamorphic rocks (the Diesel) were pushed up onto, beside and over younger rocks (the rest of the Diesel), stacking them up "roofward". This resulted in a warped compression of the crust which caused a series of deep basins to form east of this mountain front, like the Denver Basin in which sits, well, Denver. As in all things, when one side goes down, the other goes up (nature's constant need for equilibrium, called isostacy). Thus, high mountains just west of Denver and the Front Range probably moved even higher in response along faults. This process is called isostatic change. Fun stuff!

Although there is another player in this game, and that is erosion. Erosion was and is constantly trying to reduce the number of 14'ers for you to climb back down to 0. As a matter of fact, much of the entire western Great Plains region is on a foundation of eroded Rocky Mountains material. Luckily, today's Rockies in Colorado were so recently uplifted in geologic terms, that erosion has not had the time to reduce those back to obviously less meaningful 13ers. Give it a few million years though. Plus they are in many cases tough suckers...there are many Colorado mountains whose resistant peaks are composed of massive and hard igneous granites in metamorphic schists, plus sedimentary metamorphics like quartzite. Tough Tough stuff, doesn't erode as easily as, say a shale or sandstone.

That explains why high mountains are in Colorado, but what about north and west of there? What happened to poor old Montana?

If you've ever been to the Grand Tetons in Wyoming, the Bitterroots of Montana, or the La Sals in Utah, you know there are some doggone tall mountains in those states too. But not 14ers, obviously. There's nothing magical about the number 14, but we can hypothesize, that the mountains up in Montana and Wyoming were possibly off of the axis of maximum compressional stress for the subducting plate, so maybe those mountains started off just a bit lower than the Colorado peaks even before erosion's effects kicked in, or that the region had different basement rock geometries or different plate characteristics which changed things a bit there.

And of course, both of these states have plenty of soft rocks, but they also have the hard stuff too, so that's not a big factor. Anyway, these locally tall 13'ers are related to the same localized, but very recent 5 million year old fault uplifts as the ones in Colorado, genetically anyway. There are also local and regional rotational and tensional stresses at play, faulting styles, etc etc, blah blah It goes on and on and on.

Luckily we don't have all the answers. Keeps geologists employed and off the streets.

Hopefully you get the drift... just be luckily you don't have to drive too far to climb them all.

Bruner from Palm City, Florida asks:

I was wondering if you would know the name and address of a Texas Talc mine where I might purchase boulders of carving stone?  I was in Denver last week at the Sculpture Show and saw some pieces and was told it was Texas Talc.  I do stone turning and this would be a wonderful medium and beautiful material to turn.  Any help would be appreciated. 

Devin Says:

Bruner,

There are several companies that own and operate talc mines in the Allamoore Formation near Van Horn in Husdpeth County Texas, and you'll have to contact them to find out if they might provide you with a boulder-sized sample of the rock. Most companies 'flour' the metamorphic rock that contains the talc into a powder in order to extract it, and it is normally sold in 50-500 lb. bags. I'm not sure how useful native Allamoore rock would be in sculpture as it is friable and highly fractured, but I'm no artist!

But if you want to find out more, contact the USGS Talc and Pyrophyllite Commodity Center at 703 648-7722.  They can provide contacts for major talc providers in the area.

Vonnie from Maryland asks:

We'd like to find some ammonites in South Dakota/Wyoming.  Are there any  LEGAL places to hunt around without stepping on anyone's toes by accident?

Devin says:

Vonnie, 

There are several well-known ammonite producing rock formations in South Dakota. Most notably are the Pierre Shale Formation and the Fox Hills Formations, both Cretaceous in age, in and around Badlands National Park and in north central SD. Obviously you cannot collect at the national park, but you can try and get as close to those rocks as possible outside of the park. Get yourself a good South Dakota geologic map and try your luck. 

Unfortunately, I am Texas-based, and I'm not that familiar with the area and cannot recommend specific sites to try. Good rules of thumb are, 1) try public lands such as national forests and BLM lands which often allow minimum disturbance rockhounding, 2)check with the local district office, and they will often give you maps of where to find minerals and fossils. Black Hills Forest office in the Black Hills, SD, does this for sure, as I have collected there before. As for private lands, all you have to do is ask really...many landowners will allow it with assurance of minimal disturbance. 

Hope that helps!

Elwanna from Arlington, TX asks:

I was told there was a place in west Texas to crystal dig.  Do you know where that is?  I'm headed to Lubbock and would love to spend an extra day digging crystals.  

I would so appreciate your response if you have the time.  I understand just cause you are a geologist doesn't mean you know all but I'm just hoping you have heard of such a place.  

Have you considered starting a geology adventure group - they could come in behind you after you have finished filming?

Devin says:

Elwanna, 

Lubbock itself has a relatively uniform geology at the surface, but there are places with rocks and fossils (maybe not the best "crystals", but ok.) to be found within a few hours drive. 

All along the "Caprock", that eastern edge of Llano Estacado plains of Texas, one can find older Permian aged rocks containing lots of evaporite salts, such as gypsum. Gypsum yields crystals of alabaster and selenite in several places along this hundred-mile escarpment. Several spots near the town of Turkey, Texas have been known to yield nice alabaster, and gypsum is mined in the area for wallboard (sheet rock to us country-fried Texans). 

If you head northwest to Lake Mackenzie, the book "Rockhounding Texas" by Falcon Publishers reports finding selenite ("crystalline gypsum") and petrified wood in the area. This might be worth pursuing; I suggest picking up a copy of the book if you don't have it. Other towns in that area may have similar surprises; best to ask around in town to see if any locals allow collecting. 

Palo Duro Canyon is just north of Lubbock and is a textbook in Panhandle geology. Stop by if you have time, and keep and eye peeled, as geodes have been reported in the vicinity.

 Have fun!

Malcolm from Georgia asks:

Hi, I am Army Officer stationed in Georgia.  My company is deploying to Kuwait in the coming months.  I want to find out some information on sledding or boarding in the sand...the natural resource that makes up 99% of the country.  Specifically, I was looking for an idea of what type of sled to buy and where. If you have any info on this or might know where I could find some information I would greatly appreciate it.

Devin says:

Malcolm, There are several companies which make professional sandboards which have bindings to hold the board on your feet.  To name a few, try websites like www.venomousboards.com or www.oceanculture.com to browse through their product lines. 

Basically, a sandboard is a modified snowboard with a higher flanged toe and side with bindings which help offset the increased friction of the sand.  You can also substitute these special boards with the homemade kind, by finding an old snowboard (or even a skateboard with wheels and axles removed) and nailing a pair of Teva-type sandals directly to the board at 90 degrees.  This allows you to ride the "edge" while taking sand dune slopes of up to 45 degrees (which is the angle of repose of dry sand, or the steepest slope possible without the sand rolling downhill).  You'll need to get some sandboard wax or surfboard wax and wax the crap out of your board before you go, or you'll be on your face!  And take extra...sand is hard on  the wax. 

I also like the good ole cardboard box.  Get a washing machine box, cut out a view hole and fasten two old downhill skis to the bottom.  Shove off and hang on; speeds of up to 60 mph are possible at Great Sand Dunes in Colorado on 700 foot dunes using skis; who knows what you might find in Kuwait. 

Happy sand hogging!

Marge from Stafford, VA asks:

We are coming to OK/TX to look for fossils.  We are interested in sites we can explore around Texoma and Ammonites in particular.  Thanks for any help.

Devin says:

Marge, Your best bets for finding ammonites will be in the area of Lake Texoma near Denison, Tx...indeed to get to the best outcrops with ammonites one really needs a boat to examine the beaches, draws and creeks along the lake shores.  Keep in mind that it is illegal in Texas and Oklahoma to take fossils from public lands, so be sure to collect only from private areas with the owner's permission.  Most outcrops of the silty Cretaceous limestones are pretty abundant in this area beginning a few miles west of the dam.  Ammonite hunting in the area is no secret and you have to search around for the best spots, but there are plenty.  You'll want to look for rounded chunks of limestone weathering out of the weaker rock around it, best found in banks and creeks where the water action is removing rock for you. With some time, luck and a little cleaning, you can find some nice ammonites.

Sarah from Winnsboro, TX asks:

Can you tell me which event is Memorial weekend?  Pioneer Days or Chisholm Trail Round Up?  Or let me know when they are?

Devin says:

Sarah, 
The events you refer to are Pioneer Days, the annual September festival held in the Fort Worth Stockyards featuring lots of music, food, the Pioneer Heritage Village, Pawnee Bill's Wild West Show, a parade, gunfighter shows, arts and crafts, carnival rides, and cook-offs.  The Chisholm Trail Round-up, the annual gathering of horsemen and women and celebrators of the famed Chisholm cattle trail, was usually held in June, but has been postponed until 2003. This year the Pioneer Days run from Sept 13-14.

Dustin from Forney, TX asks:

Devin, where is a good place to go camping in the area?

AND... Devin, how is limestone actually formed?

Devin says:

Dustin, I'll answer both of your questions together. Limestone can be formed by several different processes, but all limestones are based on the same fundamental set of chemical components. Calcium, carbon and oxygen combine together to form CaCO3, also known as calcium carbonate, the building block of limestone. 

Calcium carbonate can form in two different ways, one chemical and one biological. Most limestone forms out in the oceans, where the shells of sea creatures such as oysters, clams etc. remove carbon dioxide and calcium from seawater and secrete a calcium carbonate mineral called aragonite to create their shells, which of course they live in. When these creatures die, they fall to the ocean floor and their shells remain, where over millions of years the pile up in the mud, the aragonite converts to calcite, and they form fossiliferous limestone. This is the most common type of limestone. 

Some limestones do not require any living creatures to form, however. Water may dissolve calcium and carbon dioxide from other rocks or soils and redeposit it elsewhere as a brand new rock, one which "precipitates" or grows under certain conditions. This can happen in freshwater lakes or streams, resulting in forms of limestone called "travertine" or "tufa" (like those deposits associated with geysers and hot springs), in the oceans under certain environmental conditions, or deep underground in caves and caverns, producing the pretty "stalactites" and "stalagmites" you see when you go into a cave. 

Other elements such as magnesium or iron can be present with limestone, creating other related carbonate rocks such as dolomite, or oddly colored limestones.  Limestones can then dissolve back into water under the right conditions, and somewhere else the cycle begins again. 

To answer your first question, I can give you some great local places to go see limestones "in the flesh" and places to camp-out nearby. Two of the most notable limestones in the DFW area are the Austin Chalk, which you can go see at many road outcrops in western Dallas county, where you can camp nearby at Cedar Hill State Park.  If your more adventurous, try Dinosaur Valley State Park, where limestones, sandstones and shales can all be seen and appreciated, with some pretty awesome camping opportunities. The region contains many good opportunities to both rock-watch and camp. I'll work on a more comprehensive list and get it up on the site soon. Hope that helps!

Kelly from Tulsa, OK asks:

This is kinda out there but when did you go to OU?  You look familiar...I was looking on here for a good place to "learn" to camp/explorer (I've always liked digging in the dirt") but have never really found any good places here in OK.  Well, anyway I saw your picture and you just looked familiar.  Well, if it turns out I don't know you; have any suggestions for a beginner?

Devin says:

"Kelly, I attended OU (The University of Oklahoma) from 1995-1999, not too long ago, so if you were there during that time it's possible you might know me! 

As for good places to learn to "adventure", Oklahoma actually has some of the best adventuring to be had in the Midwest. With 5 sets of "mountain ranges" (ok, they are hills and plateaus, but there is scenery to be had...count em, Ozarks, Ouachitas, Wichitas, Arbuckles and Black Mesa) all except the Arbuckles are dominated by Federal and State Parks. 

One of my favorite destinations within the region is the Wichita Mountains National Wildlife Refuge. This granite paradise seems to have it all; rock climbing, wildlife, camping and backpacking, scenic drives, fishing, and those tasty Longhorn-burgers up at the nearby small town of Meers (try the peach cobbler, you won't want to go home). 

If you're looking for more "backwoods" quality adventures, then try the Ouachitas or Black Mesa. The contrasts between the two are stark; the Ouachitas offer several wilderness areas with hundreds of miles of hiking and backpacking throughout the Ouachita National Forest. Several nearby state parks, such as Talimena and Robber's Cave, offer futher activities such as limited rock climbing and backcountry camping. My favorite spot is Cedar Lake, in the National Forest, a gem of a lake surrounded by forested hills. 

Black Mesa offers a much different experience. The most remote corner of Oklahoma, near the Colorado/New Mexico junction (Three corners! There's a monument there at the spot where they all meet!) is a desolate, yet beautiful moonscape of volcanic ash, basalt cliffs and high rocky plateaus. At over 2.5 hours from any city over 20,000 people, this is one place to truly get away from it all. This is, in my opinion, the BEST stargazing location in the the Southwest, as it's clear skies, higher altitude and distance from people make the sky light up with stars. 

So in short, for the beginner adventurer, my advice is simple; just get out there. Decide what you want to do (camp, hike, stay in your car, or dig for minerals, whatever your impulses demand) and as the saying goes, just do it."