Reflections on Working at Aniakchak
U.S. Geological Survey, Alaska Volcano Observatory
After months of planning our first camping expedition into the Caldera, my vision of Aniakchak was still based largely on photos, the very few written descriptions available, and the stories. Everyone had stories of wind and rain and bears and flying pumice and previous visitors driven mad by the ceaseless, tent-flattening gales that roared into the Caldera. Sure, there were stories of calm and beautiful days, but because I am the quintessential "safety-bear," I fixated on the other extremes. So, when we piled our mountain of gear into the faithful blue Katmailand's Otter in King Salmon, with a slowly dissipating scud to the south telling us to hurry into the air, I definitely had a pit in my stomach.
I was anxious, but also excited. As a volcanologist, Aniakchak was known to only a handful of my peers and the details of the volcano had yet to be explored with modern means and modern understanding of volcanic processes. My colleague and companion, Game McGimsey, and I had read every tale written by Father Bernard Hubbard, SJ, the hyperbolically adventurous amateur geologist and Jesuit priest from Santa Clara. We had combed the sparse existing scientific literature dating back to the 1920s. We had some notions of what we'd find, but largely our minds were open and ready to observe and understand.
Droning above the tundra and flitting in and out of cloud edges, our crusty old pilot calmly asked us to let him know if we saw any oil streaming from the engines. With John Eichelberger, from the University of Alaska at Fairbanks (UAF), we were packed into the back of the Otter with our Weatherport, camping gear, and food for several weeks. The approach to Aniakchak takes one over wind-scoured, increasingly barren, ash- and pumice-covered flatlands, and then the terrain rises and deep gulleys begin to expose layers of volcanic deposits, the succession of clues to eruptions past. With little warning, the Otter burst over the rim of the Caldera and there before us was the crater; still looking like a photograph, but impressive in its size and depth from our truly bird's eye view. John made a quick turn to land on quiet Surprise Lake and we commenced a rapid unloading, ever mindful that weather could pour in at any moment, trapping our Otter. Soon we were alone with a pile of stuff, the airplane's noise quickly fading as it zoomed through the dramatic gash in the east rim, the Gates.
We set up camp quickly and it was late afternoon before our Weatherport and personal tents were up and secured (or so we thought, until the first big blow flattened the back panel of the Weatherport). We took advantage of the solstice hours to climb up Vent Mountain, a great place to get an idea of the incredible volcanic scenery. I remember returning to camp near midnight, the light dimming slightly behind gathering clouds. I was tired, amazed, and excited at our task ahead; telling the story of this beautiful place.
Over the next few summers, Game and I worked both alone and with other colleagues inside, on the rim, and around the Caldera. We were treated to a few distant bear sightings, sudden meetings with lone and small bands of caribou kicking up the ash as they pranced across the pumice plains. An eagle once swooped low and fast over our heads en route to plucking an unwary fox pup from its den, a scene rendered heart wrenching as the mother fox followed, yelping and dashing in vain after the predator. Steadily we mapped, sampled and analyzed the various volcanic units and determined ages of some of the larger eruptions within the last 3,500 years. The goal was to determine the history of the Caldera to help us evaluate future hazards from eruptions. Aniakchak is remarkable for the diversity of its eruptive stylesincluding its only historical eruption in 1931 that blasted two new craters through the Caldera floor and blanketed much of southwestern Alaska with ash. Inside the Caldera are classic dacite lava flows, near-perfect strombolian scoria cones, sublacustrine lava domes, tuff cones, and an eviscerated dome and flow complex called, simply, Half Cone.
Camping and working inside the Caldera was a profound sensory experience. My emotional highs and lows mirrored the wild weather and the pace of our understanding of the geology and moods of the volcano itself. Our camp suffered only one bout of damage during a classic windstorm. From this we learned how to really anchor a Weatherport so that walls wouldn't come apart! I learned to sleep with the yellow tent walls occasionally pressing against my face as I lay snug in my REI Volcano sleeping bag. On nights when I could hear the gentle lapping of Surprise Lake and Game snoring in the tent a few yards away and I knew the weather was good and all was well.
One evening, Game, a geophysicist colleague, Carrie, and I sat on the ridge above camp and watched a glorious full moonrise over Black Nose, the towering, dark promontory of volcanic rock that stands high above the south side of the Gates. The air was calm and the temperature a comfortable one for an early summer night on the peninsula. At that moment, gazing up at the bright white disk and its finely etched impact crater-forms visible to the naked eye, Aniakchak, with the summer dusk illuminating its Caldera floor and walls, seemed the perfect planetary link, an observation made by Hubbard sixty years earlier.
One of the joys of doing geology is exploration and we were fortunate and observant enough to make some new finds. We discovered a debris-covered glacierlargely inactive at presentnestled against the precipitous south wall of the Caldera. Our clues included a field of conical mounds of pumice, the result of differential insulation and melting of the icy substrate, as well as a bottomless hole that revealed, upon closer inspection, classic blue ice. Needless to say, we walked across the surface with more care after that!
Perhaps the most wonderful moment of discovery came as we sat one calm afternoon high atop Surprise Cone, so-named by us for the large, variously colored pumiceous bombs from Half Cone we had discovered on the top. Game had been stewing for some time about the morphology of the crater walls. From this perch, he and I could survey nearly the entire Caldera except for the portion hidden behind Vent Mountain. He noted a subtle but consistent terrace or bench high above Surprise Lake. Using our hand as levels, we could follow this feature, albeit discontinuously, around the eastern inner Caldera wall towards the Gates, where the equivalent altitude coincided with another prominent bench. Game surmised that this could be the telltale mark of a formerly deep lake within the Caldera. Over the course of the next few weeks, as we wandered and mapped features and deposits, we clarified and furthered this observation, adding evidence that, indeed, a deep lake had once filled perhaps much of the Caldera. We found lake clays buried by young Half Cone debris, now tens of meters above the modern level of the lake, and subtler terraces that might indicate higher water levels. Textures of some of the lava domes suggested underwater emplacement. The story was hanging together.
To be fair, others had suggested that a lake once existedit would not be unusual because these enormous collapsed calderas often contain water (e.g. Crater Lake in Oregon). However, no one had put the observational evidence togetherand as we gathered more clues, the story became more and more compelling. What had happened to this water?
Game began to suspect that the deep V-shaped notch at the Gates could have formed catastrophically, perhaps in a sudden biblical draining of the large Aniakchak lake, an assumption supported by the geological evidence. We realized that to investigate this hypothesis, we needed to spend time along the Aniakchak drainage. We had run out of time that summer, but on the flight out, we had a brief glimpse down the Aniakchak River and spied enormous boulders of Caldera-rim rock scattered like child's blocks in the upper drainage, and a deep channel cut into the ash flow sheet. In the back of the plane, stuffed amid the piles of gear and rock samples, Game and I looked at each other and smiled, knowing that we were onto a wonderful story, the kind every geologist yearns to tell. Details would have to wait until the next field season, but this flush of excitement, as we turned north for King Salmon, softened our sadness at leaving such a moving and powerful landscape.
Last Updated: 03-Aug-2009