The Long Way Home: Big Bend National Park

Editor’s note: Ocracoke Islanders Tom and Carol Pahl are on a trek around the United States (following 70-degree weather) and will report back from time to time their reflections. This is their sixth dispatch.

Text and photos by Tom Pahl

In February, after we left the gulf coast of Texas and started inland, we finally came to the West. Suddenly the sky-scapes got bigger, the views across the land grew longer and my problems seemed to grow smaller by factors of a thousand. 

From Aransas, we headed to Big Bend National Park, with a stopover at Seminole Canyon.  Our eastward adventures were all about places that we were experiencing close-up, enjoying the sunshine on our faces, learning about local history, watching out for gators and snakes, finding great bike trails, birding, trying to stay warm. 

But once we got to the West, once the vistas expanded past comprehension, our adventures have become overwhelmed by the record of eons, by counting time in hundreds of millions of years, by looking at a line of ancient volcanoes disappearing into the horizon, by uncountable layers of limestone, hundreds of feet thick, over a mile above sea level where once a huge ocean stood, filled with shelled animals filtering out calcium carbonate in minuscule amounts, building future mountain chains. It is all simply impossible, and yet there it is.

I have this flinty soil in my blood, being Montana born and raised. And every time I go west, it feels like coming home. My dad was a geologist and an educator. So, whenever we traveled, we had to expect that there might be a sudden slamming of the brakes and craning of the neck. We–-two siblings, myself, and my mom – would, of course, have missed the significance of whatever geological wonder lay before us. My dad would hop out of the car, rock hammer in hand and rush over to an outcropping or to an entirely unexceptional-looking field of stones and start digging, chipping, collecting. He’d pile a load of rock into an always available milk crate, grinning like he’d just found a lode of diamonds. “Feldspar,” he’d say, or “smoky quartz,” or something.

The other day I stopped at a rock shop in Arizona and, not surprisingly, I came out rock-less, because who wants to buy an agate when there is so much joy in finding one. But I did come out with a rock hammer. And now I too can jump out of the car and start chipping away at geologic mysteries.  Except that 60 years ago when my dad was rock hounding, you could stop just about anywhere and grab a crate full of stones and nobody would care. Now, it seems every rock has an owner. 

Big Bend National Park is stunning. Everything is so big and we, in our little pick-up truck, were just a speck somewhere among the wonder. You can take off into the wilderness on some dirt road that brings you through a burning desert teeming with prickly pear and cholla and ocotillo cactus, creosote bushes and agaves.  You drive through ancient lava beds while overhead the remnants of a thirty-million-year-old volcano hovers above so mightily that it blots out the sun.

A thumbnail sketch of Big Bend’s geologic history would include two periods of oceanic inundation and two periods of mountain building. The older, more significant, oceanic period goes back to the early Paleozoic, some 500 to 600 million years ago. The area, and most of what is now the American west, was covered in ocean for a couple hundred million years. And the really odd, really amazing thing is: The North American continent itself was drifting around, on vacation somewhere in the area of what is now the Polynesian Islands in the South Pacific, enjoying the tropical environment.  Its ocean was shallow and, where the land rose above the water level, trees and tropical plants grew densely.  Early amphibians, fish, and shelled sea creatures plied the waters.

Over the next couple hundred million years, the continent drifted northward and eastward, eventually colliding with another plate which also happened to have been drifting about the globe pretty aimlessly. That collision resulted in the first of the mountain-building events in the Big Bend area, the formation of the Ouachita Mountain Range, some 300 million years ago. It also helped to create the super-continent called Pangea, which eventually would be broken up to form North America, South America and parts of the African and European continents. It was a big deal at the time.

When continents collide, one landmass pushes under the other, raising up mountainous formations and not inconsequentially, cutting through the earth’s very crust, allowing magma to escape to the surface in the form of massive explosions and huge flows of molten rock, gases and ash.

But as we know, nothing lasts forever. The volcanic rifts healed, the magma quit flowing and a period of relative calm descended on the area.  For the next 200 million years or so, the quiet forces of erosion, from wind, rain, temperature change and gravity chipped away at the mountains, taking the easy parts first.  Whatever could more readily dissolve, crumble, fall and wash away was transported into the lowlands, creating layer upon layer of sand and mud. The remaining, harder rock was broken up as well, just more slowly, some of which is there even today in the older formations still visible at the park.

Meanwhile, Pangea continued to drift and twist like a sheet of ice might drift on a lake, forming and deforming into the continents we know today.  About 70 million years ago, the North American Plate happened to bump into its neighbor to the west, the Pacific Plate, causing a good amount of consternation which we haven’t yet fully overcome. The Pacific Plate “subducted” beneath the North American Plate at an unusually shallow angle, resulting in mountain uplift hundreds of miles east of the fault, creating the modern-day Rocky Mountains. 

That huge tectonic collision 1,000 miles from the park eventually set off a new series of geologic events in Big Bend. For a few million years the area was again covered in sea water, and then about 30 million years ago, a “regional crustal extension” occurred, tearing apart the remnants of the ancient Ouachita Mountains and once again opening the earth’s crust to massive volcanic explosions.

Most of what we see today in Big Bend National Park is the result of that volcanic activity, a relatively short 30 million years ago.  A line of volcanic cones rose up thousands of feet and spewed millions of tons of molten rock and ash into the desert below. Eventually, though, each of the hundreds of volcanoes simply ran out of juice and pushed up its last cone of lava which hardened in place.  The huge towers of rock now standing like massive sentinels in the desert landscape are the remnants of the last gasp of each of those volcanoes.  Originally mountainous forms, peaked with a crater at the center, the ash and magma that made up the sloping mountainsides has eroded away, leaving behind straight-sided monoliths of hardened lava, many still rising thousands of feet above the desert floor.

Every rock, every mountain, every grain of sand, every mineral and crystal on earth can trace its lineage to the earth’s core, to the magma that flows from between the tectonic plates.  It is transformed by erosion, by heat, by pressure, by dissolution, by chemical processes and by physical processes into the vast array of rocks and minerals we see around us every day.  From the plainest chunk of basalt to the most fantastic glow-in-the-dark magical mineral, it is all earth. 

All, that is, except for the thing I found one day while I was hiking in the desert.  I picked it up, thinking it was too heavy, too dense and too unusually textured to ignore.  And so it was that I held a meteorite in my hand.  It contains enough iron that even a small magnet grabs hard to it. It has a glossy surface transformed by the heat of entering the earth’s atmosphere.  It has a flat side where it slammed onto the desert floor, hot enough to deform and fuse a layer of sand before cooling. Nearly molten iron. A visitor from outer space.  A rare exception to the rule.

Day after day, as we travel around the country, we get to see fantastic views, meet interesting people, experience the adventure, and feel the wonder.  How lucky I am to have picked up a meteorite.  And how lucky we are to be able to do what we are doing!

The scale of time, the mass of the structures, how easily it can take your life away, the awesome beauty, the simple beauty, the constant change, the everlasting foreverness of it all. 

It’s humbling and awakening. 

Sources used in this article: 
The Field Guide To Geology, David Lambert, Checkmark Books, 2007;
National Park Service, Department Of The Interior, NPS.gov-geodiversity-atlas-big-bend;
USGS “Digital Database of the previously published geomorphic-structural map of the Ouachita Mountains” 2002; and other readily available sources on the internet.