Geological wonders of Alaska
“The mountain is out guys”, popped a message on the WhatsApp group from our tour leader Brianna. She had stepped out earlier in the morning to drop a few group members for the flight tours. I, for my part was still coping with a very cold August morning in Talkeetna. But as I saw that message, I ran. Ran through the woods on that muddy trail I swore never to cross alone, ran past the smell of freshly brewed coffee and savory crepes in town center and reached the banks of the silt-laden river Talkeetna. There it was, Denali — The Great One.
Towering over all other peaks in the Alaskan Range, Mount Denali is the highest peak in North America (6191m). However, measuring from the base to the summit, it is actually a mile taller than Mount Everest. This 60 million years old mountain has wonderful tales to tell. Tales of its birth, growth and shape which later branched out to give birth to the stories of numerous glaciers, rocks, lakes, and vegetation in Alaska.
Last month I visited the 6-million-acre large Denali National Park, home to this majestic mountain. As I stood on mile 66 at Eielson Visitor Center watching Mt. Denali up close, it mesmerized me with its grandeur, gorgeous neighborhood, and tundra décor. Unable to take my eyes off it, I walked downhill trying to get as close to the mountain as possible when it whispered in my ear, these forgotten stories.
Mount Denali
Once upon a time there were two tectonic plates. One carrying the Pacific Ocean and the other carrying North America. Floating carelessly on the molten mantle of the Earth, they had an encounter one day. The subduction from that encounter caused tension so high, it gave birth to the entire Alaska Range.
In the debris carried around by the Pacific plate, there was a granitic pluton. The low density of granite already ensured that it floats above other rocks in the earth’s crust and the tension of the collision helped it rise to the surface and became Mount Denali. The igneous granite is also resistant to erosion thus helping Mt Denali fight the forces of nature and keep its tall stature intact.
Back in the day, precipitation on Denali happened in form of ice and snow. Due to extreme cold at the higher elevation, there was no melting, and a heavy mass was accumulated which eventually compressed under its own weight and started flowing through the stream valleys. Such river of ice is called a Glacier. Denali is home to enormous glaciers spanning 45 miles long and 3,700 feet thickness.
Years passed by and Denali kept getting sculpted by its glaciers. As they flowed downhill, they picked up rocks from its bed, grinding away some to silt and plucking others large chunks in their entirety. With the melting of the glacier, the silt made its way to the streams giving them a “milky” hue and the large chunks were left as “erratic” rocks in an alien terrain. The carving of these rocks left behind ridges. The molten ice in one of those ridges is now the Wonder Lake.
Muldrow Glacier
When the NPS tour guide pointed out a vast glacier at the foothills of Mt Denali, my eyes probed for the shiny blue crystals usually characteristic of a glacier. But Muldrow was black.
What appeared black on the terminus was not ice though, it was tundra vegetation underlain by ice, narrating the tale of the times when Muldrow decided to break all the rules and surge.
The prevailing theory of a surge is that the natural advance of a glacier causes friction, which melts the deepest ice. Loose gravel traps the meltwater underneath. But at an exceedingly high elevation as that of Denali, ice accumulates and thickens on the upper glacier over many years with only a slow flow or transfer of ice to the lower glacier. At some point during this quiescent phase, the glacier thickness reaches a threshold causing a surge. The surge redistributes that mass to lower elevations, with the help of the meltwater serving as a lubricant, sliding downhill at a rate of about 30–60 feet per day, almost 50–100 times more than the normal rate.
At the Muldrow glacier, the upper 27 miles currently flow slowly but constantly downhill as with any ‘living’ glacier. This movement carries away rocky debris and inhibits the growth of vegetation that might otherwise become established. However, the lower 7 miles of ice and debris are stagnant, having been deposited during glacial surges as far back as 1,800 years ago and not moved since. This resulted in the growth of the tundra shrubs that gives Muldrow Glacier its abnormal black appearance.
Resurrection Bay
If there is a marine equivalent of the enchanted forest, it is the Resurrection Bay. The 6 hours cruise of the bay, unfolded before my eyes the geological wonders inhabited by a very diverse aquatic wildlife, making the entire experience little short of magical.
To start with, Resurrection Bay itself is a fjord — a long deep, narrow inlet of sea between high cliffs. A fjord is formed when a glacier retreats, after carving its typical U-shaped valley, and the sea f ills the resulting valley floor. The water of Resurrection Bay is significantly deeper (almost 1,000 feet) than the surrounding continental shelf.
On the east side of the bay, Cape Resurrection presents a massive, sheer cliff to the pounding of the waves. The rock here is pillow basalt, a type of igneous rock that was formed when lava flowed out underneath the water and cooled rapidly. The bubbled texture of the cliff provides an ideal habitat for nesting birds like black-legged kittiwakes and horned puffins. On the opposite side, the shore is eroded into spires, cliffs, and cove. Exposed areas reveal buckled layers of ancient sediment. Mud, transformed by heat and pressure, becomes shale, a fine-grained, dark-colored stone with many thin layers.
Round the corner to the west, moving out of Resurrection Bay, Cape Aialik juts into the tumultuous water. The rock here is granodiorite which is resistant to erosion. Chiswell Island made entirely of granodiorite thus makes a stable habitat for the puffins, murres, and auklet. Sea lions, too, congregate on smooth granitic slabs washed by ocean swells to mate, give birth, and rest.
As we moved past the Chiswell Island, watching the silver salmon jumping out of water to splash off the sea lice and otters floating on their backs in a posture of serene repos, someone spotted a humpback whale. The 40 tons glorious creature moved gracefully as curved light in the water, its slick, black back rising and falling until finally it showed its tail and dove.
But the most ancient and the most incredible wonder on the Resurrection Bay was yet to unravel — The Aialik Glacier.
Aialik glacier flows southeast for about 4 miles from Harding Icefield to Aialik Bay and reaches tidewater at the extreme head of Aialik Bay. The glacial font is an ice cliff about 200 feet high that is constantly discharging ice with activity peaking during summer month. From the cruise boat I was watching the mammoth when suddenly it got really loud. The experience of hearing a glacier pop, crack, and boom escaping the air that has been trapped in that ice for 10000 years is unlike any other; especially when the falling ice causes ripples in the water beneath your sea vessel.
Tidal bore at Turnagain arm
The conventional way for the river is to flow from a higher elevation to the ocean or sea. But sometimes an aberrant tide, empowered by the full moon, decides to change the rules of the game, and pushes up against the current into the stream.
The most famous one amongst them is the tidal bore at Turnagain arm. Running at the speed of 10–15 miles an hour, this tide can rise upto 6–10 feet high. The Turnagain Arm bore wave is the only one that occurs in the far north and the only one bordered by mountains, making it the most unique and geologically dramatic bore tide in the world. Harbor seals often ride the tide into Turnagain Arm, and beluga whales may come in a half hour or so later once the water gets deeper to feed off fish giving a glimpse to their beauty to all of us passing by on the highway.
Fascinating, isn’t it? The mighty natural forces and their creativity we came across in the stories above can cause a change of heart of any nihilist. These natural phenomenon open your eyes to the triviality of our existence. And yet, our trivial existence has resulted into an existential crises for these mighty forces. Human being is the virus for Nature. As we multiplied and mutated, we kept killing every organ vital to the existence of the ecosystem. And just like covid attack the lungs and deprive a human of oxygen, we have hit the source of life for this ecosystem, glaciers. Thus, the last story I am going to tell is rather anti-climactic. It is the story of the one called Exit Glacier. While the name came after a homesteader expedition used it to exit the ice field, the irony of its name comes from the fact that it is the first one to make the grand exit from Earth’s ecosystem after man-made climate change did not leave it a choice.
Exit Glacier
Exit Glacier, a finger of cracked, blue-white ice that drops out of 700-square-mile Harding Icefield, is relatively small, only 14 square miles. Not it’s significance though. The approach to Exit Glacier, the most accessible of the 500 square miles of ancient ice covering Kenai Fjords National Park, is a timeline of retreat. On the road to the glacier’s toe, on the trail winding below the forest canopy and, ultimately, on the mostly bare rock at the end of the trail are signs marking 195 years of accelerating glacial retreat.
Exit Glacier is not Alaska’s only walk-up glacier, albeit with a walk that has been getting longer as the glacier shrinks. It stands out for its location in an easily accessible national park, the in-your-face documentation of its retreat and its role as a real-time climate change laboratory.
A pavilion built in 1987 to give visitors a place to rest in the shade was originally situated to provide a good view of the glacier; now the view is of alders that hem the structure after springing up in ground uncovered by the glacier’s retreat. On the mile-long Exit Glacier trail, which once ended in a loop, the Park Service has had to make two significant extensions, adding a 540-foot spur in 2006 and a 420-foot extension of that in 2010. And even beyond this last sign that marks the 2010 edge, there is a fissure of open space showing how Exit Glacier has continued its retreat up the valley in the last decade. In fact, in the no-travel-no-commute-no-pollution year of 2020, Exit Glacier retreated the most ever — 256 feet.
I must be 10 years old when my father explained to me the concept of Ozone layer and the damage its depletion can cause. 25 years later in 2021, I eye-witnessed that damage in the delayed monsoon in India, forest fires in Sibera, record high temperature in Alberta Canada, smoggy skies in Pacific Northwest America and in sweetening Pino Grigio in Italia. But never ever, it felt so real and apocalyptic as it did in Alaska, standing next to that 2010 sign.
