Saturday, January 24, 2015

Under the High Plains Sea

The other day I wrote a post called Why I Believe Crazy Things. My point was that science is full of ideas that sound just as crazy as anything you'll find on the "Strange Phenomena" shelves in the New Age section of a bookstore. If you think about it, the idea that the universe exploded into existence from a single, tiny point sounds crazier than the idea that bigfoot roams the Pacific Northwest. It's just that in science, we also have evidence for those crazy ideas. There's solid evidence for the Big Bang, but not for the Big Foot.

Another point I've often made lately is that science lets you see beyond surface appearances and find marvels in what might otherwise seem mundane. A house down the street from me, for example, is made of an unexceptional-looking rock that was formed in a single cataclysmic day, when red-hot volcanic ash came roaring out of the mountains and buried what's now Castle Rock, Colorado. The rock doesn't look that interesting, but it is when you look beyond the surface.

So, two points: 1. Science shows you the stories beyond surface appearances. 2. Those stories are often really bizarre.

The other day, I came across a good example of both of these of these points. The crappy little cellphone picture above shows a section of high plains just southeast of Colorado Springs. The little bumps are known as the Tepee Buttes. They're not very impressive, even in good pictures. They're only about thirty feet high, and if you turn and look the other way, you'll see Pikes Peak in all its magnificence. So why notice them at all?

They're worth noticing because if you know the science behind them--if you go beyond surface appearances--you find one of those bizarre, hard to believe stories. It turns out that those little buttes sitting there on a mile-high plain, were once communities of freaky creatures living on the bottom of the sea. This was about 75 million years ago, when a shallow sea called the Western Interior Seaway covered what's now the North American plains.

"Lamellibrachia luymesi" (Click for photo credits)
Each butte marks the location of an ancient sea floor vent called a cold seep, where methane and other chemicals would seep out of the the ground. Some bacteria (then and now) can live on those chemicals--they basically "eat" methane and hydrogen sulfide. As they did so, they created growing mounds of limestone on a seafloor that was otherwise mostly mud. That's why the buttes are now limestone outcrops in the middle of a great expanse of shale. But it wasn't just bacteria. There are (then and now) clams and tubeworms that form symbiotic relationships with the bacteria, so they too can live solely on methane or hydrogen sulfide. The photo to the right shows a modern cold seep community in the Gulf of Mexico.

It's weird enough that there are communities of bacteria, clams, and tubeworms on the seafloor today, living on chemicals leaking out of the ground. But it's even weirder that there are fossil versions of these communities on the high, dry plains at the foot of the Rocky Mountains.

So why believe such a tall tale? Because you can go out to the Tepee Buttes and dig up fossils of the clams and tubeworms. If you have the right equipment, you can slice open the rocks and find fossils of the bacteria that formed the backbone of the community. The evidence is right there, solid as a rock, because it IS rock.

Of course, a lot has happened since Colorado was a shallow sea. A few million years after the Tepee Buttes were living seafloor communities, tectonic forces from the west coast started reaching the interior of the continent, and the Rocky Mountains began to rise. All of Colorado--mountains and plains--were gradually lifted high above sea level. But the Tepee Buttes still sit there, telling us how the high plains were once a sea floor. They're more interesting than they look, and when you look beyond surface appearances, the tale they tell is truly strange. Strange, but true.


Tepee Buttes: Late Cretaceous Submarine Springs of El Paso and Pueblo County

Tepee Buttes on our Horizons

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