Expeditions in Time
Part I. Grand Canyon Expeditions. Of course, it's not going to be about splashy adventures, near misses and honest to god mishaps, nor the eight hardy and idiosyncratic souls in our little troupe, or 23 nights spent sleeping on the ground. It's going to be about rocks. Time and rocks. Water, time, and rocks, because after 22 days, 280 river miles, and some 160 rapids, I learned that the Grand Canyon is mostly about rock, and having the rare opportunity to immerse yourself in Earth's ancient past. And as such, a Grand Canyon Expedition extends far beyond just what's at the surface.
Part 2. Sixty-five miles down the river, and 3,400 feet below the rim. Here, beautiful river has cut down to beautiful rock, and in the process sliced through 1.1 billion years of earth history. Of course there are missing chapters in this book, but enough big chunks remain to make the profoundness of Earth and time as obvious as can be. A big boulder of Dox Sandstone (member of the Grand Canyon Supergroup) reclines here next to the channel, living out the last days of its 1.1 billion year existence as it winds down its journey toward becoming sand. This rock's time on earth has been eventful: full of squeezing, cementing, tilting, infiltration, encrustation, fracture, and now, grinding down. You can see it written in the swirls and cracks, the pits and crystals. The culmination of its many years is to be carried downriver, just the same as us as we float on by.
Part 3. Grand Canyon Supergroup continued. Still at mile 65, and looking deeper into the sedimentary Dox Sandstone because it looks like a chunk of space chock-full of galaxies is lying there at my feet, with the river lapping nearby. Smaller chunks of other supergroup members crowd up against it. Then there's the cryptic message written on a nearby boulder. My instinct is to find a supernatural explanation, maybe ancient space travelers sending us a communication in rock, something like "... space... don't go". My rational side suggests an internet search, which turns up manganese oxides, telogenesis, hematite, rainwater, leaching, fractures, saltwater, organic deposits... almost as far-fetched, but give them enough time—1.1 billion years—and they can create masterpieces.
Part 4 Grand Canyon Expeditions. What could be more terrifying than the words "Vishnu Schist"? Especially if you're heading for it at high speed, on a synthetic rubber bubble....okay they are very durable and they bounce, but still... We had a day to think about the upcoming Granite Rapid—at mile 94—and explore nearby Monument Creek, where great examples of the dark Vishnu Schist and its buddy the pink Zoroaster Granite intertwine. They're the oldest things in the Canyon, at 1.6 to 1.8 billion years old, and had first outcropped at river level back near mile 78. These hard, metamorphic rocks made for hard rapids that roared and rocketed through the narrow, sheer-walled canyon they'd formed. The dark, foliated schist has come a long way from its pre-pressurized existence as mudstone and shale, the granite no longer recognizable as the former blob of molten crust squeezed into the schist's fissures and cracks. Now here in the side canyon, they pose for admirers, let themselves be examined, and show off their scars and wrinkles from adventures down under.
Part 5. Cardenas Lava, captured in cold, hard rock for 1.1 billion years. It's so well preserved in this chunk you can imagine what it looked like as it oozed across a sandy landscape, then firmed up, all dark and coarse-grained. Scientists say it formed from subaerial eruptions of basaltic magma in a wet coastal environment. That was back when life was just figuring out sexual reproduction and colonial living. Visualize mounds of photosynthesizing cyanobacteria growing in shallow waters, the only living thing in this lava's way. It sits at the top of the Grand Canyon Supergroup, slathered like frosting on a big chunk of layer cake that slouches at a tilt of 15 degrees off horizontal. Buried, lifted, faulted, tilted, ground down flat across the tilted strata, buried again, now lifted once more—it's been a long journey above and belowground. And now, when it finally pokes its head up aboveground again, there are cactus, ocotillo, rattlesnakes, desert bighorns, and river rafters to contend with.
Part 6. Mile 109 downstream, and up a little side canyon through which Shinumo Creek flows. There are some mudflats here, seemingly left high and dry, but recently unearthed from back in the day when stromatolites and cyanobacteria ruled. Once again, we're headed back 1.1 billion years, give or take, this time to the Comanche Point Member of the Dox Formation. Like pages in a history book, each member tells a little bit of the story within the chapter that covers the broader formation. This rock with its desiccation cracks is maybe a sentence or two about being a coastal mudflat that dried in the sun, its clay contracting as the moisture evaporated and summer progressed... just like mudflats of today. If this is just a sentence on a page, think how thick the entire history book for the Grand Canyon must be! Over a mile, give or take, and it's bursting with pages and chapters—members and formations—just waiting to be read by those who have an interest.
Part 7, Expedition Finale
Yes there were swimmers, lost gear, near misses, and grinding headwinds... all the trials boaters normally run into on the Grand. Big adventures and little discoveries scattered throughout the many river miles and side canyons. I just took pictures of interesting looking rocks, only vaguely aware of what they were, but struck by how they looked. It was usually something about their color, texture, pattern, that was intense, graphic, and proclaiming "There are deeper stories here!" And that proved to be the case. Now, back on the couch, I've had the time to dig into these stories. They range from ancient Dox sandstone that has undergone nearly every alteration but metamorphosis, to Cardenas Lava that looks 1.1 billion years fresh. From the tortured Vishnu schist to the Zoroaster Granite which sealed its wounds. And from mud cracks frozen in time to this collection of landslide rubble, frozen in travertine. It's a geological doozy: classic Grand Canyon limestone, maybe Kaibab, maybe Redwall, possibly Muav, that fractured and tumbled downhill, long, long ago. Some unknowable time afterwards, it was cemented together as mineral-laden groundwater seeped through to create sedimentary breccia. Now it's unearthed for all who would visit Elves Chasm (mile 117) to scramble over.
There couldn't be a more yin-yang juxtapositioning than this: it's solid rock vs fluid river. It's living vs nonliving. It's loose rock in the background, and cemented rock in the foreground. And above all, it's the ancient past vs the here and now, and how they are all intermingled in a never-ending cycle.