Eagles & Kings:
Georgia Strait & Puget Sound
by Steve Yates
Excerpt from “A Sea is Born”
Imagine standing on Liberty Cap, a snow covered ridge near the very top of Mount Rainier. Legs and lungs ache from exertion in the thin air almost three miles above Puget Sound. Behind and just a few hundred feet higher stands the windswept rim of Columbia Crater — at 14,410 feet, the highest point for a thousand miles in any direction.
Surrounding us is a panoramic view that every climber seeks but few have savored. For the sky today is clear of clouds in every direction, and the mountain has not created its own devilish weather. No pinkish-brown smog from freeways, factories, or slash fires blankets the low-land valleys.
On this ideal day we can see for hundreds of miles to the horizon through the clear thin air. Northward, the mile high sawtoothed backbone of the Cascade Mountains - topped by 10,800 foot Mount Baker and 10,500 foot Glacier Peak - stretches 150 miles to the Canadian border.
To the west, across Puget Sound and the broad Puget Lowlands, the snow capped Olympic Mountains catch the first morning light. From the lowlands, these 7,000 foot mountains stand impressively against the western horizon, but from this distance and Mount Rainier's imperious height, the range seems a mere roughening of the landscape.
To the south, Mount St. Helens - its top blown off just a dozen years ago — offers a view into its huge, lopsided crater. Even from 50 miles away, and a decade later, the once symmetrical volcano is an open wound, and the gray moonscape north of it a visible scar — proof that the dormant dragons below our feet sleep fitfully here on the Pacific “Ring of Fire."
Though Mount Rainier's rock seems solid, you might glance hack nervously at the double circle of craters that mark its peak. Steam escapes from vents there, as it does along the volcano's flanks. Just 6,000 years ago - a geological eyeblink - an eruption of steam blew a thousand feet off the top of the mountain and sent the massive, heat induced Osceola mudflow rolling down the Carbon River Valley, covering more than one hundred square miles of land with mud to depths of more than 70 feet. The last eruption of Mount Rainier to leave significant traces of pumice happened about 2,000 years ago, though a number of smaller eruptions have occurred since. The latest evidently took place between 1820 and 1854. Rainier, too, could wake at any moment.
The terrain before us sweeps downward at dizzying angles over a jumble of blinding snowfields, glacial fingers, knife edged ridges, deep valleys, and glittering lakes. Gravity's agent has sculpted these mountains over the millennia since they were thrust high above sea level by the collision of continents and the upwellings of magma and ash. The agent? Water, in all its guises: rain, snow, ice, and glacial meltwater.
Invisible vapor is lifted from the vast surface of the Pacific Ocean by the sun, swirled into low-pressure whirlpools, and swept inland as dark atmospheric waves to lap up against the mountainsides. As the moisture laden air rises up the mountain flanks, it contracts and cools; the vapor condenses into water droplets or flakes of snow, and falls seemingly without letup - from October to June. It is hardly surprising that the desertlands east of the Cascades or the land and waters northeast of the Olympics and the mountains of Vancouver Island are arid, for the western sides of these mountains catch all the rain.
Above the shifting freezing level, precipitation falls as snow. At the highest elevations - as here on the top of Mount Rainier - the snowpack builds up each long, cold winter faster than it can melt in the brief summer warmth. Rainier, in fact, has recorded almost 100 feet of snowfall in one year (1971-72) and averages 53 feet per year; more than any other place in the continental United States.
Freshly fallen snow is only a tenth as dense as water. But as it piles up, highly compacted granular snow (firn) can become half as dense as water. As the firn is packed further, it recrystallizes, forming larger and larger crystals, squeezing out all the air spaces between. At a depth of 40 feet or more it becomes solid glacial ice, almost as dense as water or rock.
But the solid seeming ice is not rock solid. Near melting point, the rounded ice crystals slide over one another, and the ice gradually deforms — like warm plastic or iron in a forge.
The heavy ice mass slips fitfully downhill incorporating the weathered rock beneath it unto its rough underbelly. As it slowly but inexorably rasps the surface, the glacier sculpts the landscape over which it moves. Sunset Amphitheater, just below a 500 foot sheer rock wall to our left, is a fine example of a cirque — a typical bowl like form excavated by glacial ice. A glacier cuts most efficiently where it is thickest and flows fastest — midway between the snow accumulating at its head and the wasting at its lower end, or toe. It typically sculpts a series of bowls along its path, similar to the way a stream carves a series of falls and bowls as it flows over solid rock. Twenty-six separate glaciers flow from Rainier's icecap, like some multi armed albino starfish. Of these, Emmons Glacier behind us, which flows four miles due east, and the Carbon Russell system to our right, extending six miles north, are the largest glaciers south of Canada.
Yet these impressive glaciers, like those on Mount Olympus and the thousand or so smaller glaciers in the North Cascades and southern Coast Mountains, are only remnants of mightier ice fields in the past. The tall, exposed rock walls of Sunset Amphitheater below us are proof that much larger glaciers once filled these mountain cirques.
For the period from about 22,000 to 18,000 BP (Before Present), world temperatures fell lower than at any time since. And though the average temperature drop was just 10° F (6°C) colder than at present, it was enough to greatly shift the balance of winter snowfall and summer melting.
Why such long term ups and downs in the world climate? The causes are still poorly understood, but climatologists suspect a combination of reasons. The earth is not always the same distance from the sun, and it cools off at maximum distance. It periodically passes through clouds of cosmic dust, which block the sun's rays, as do major periods of volcanic eruptions. And the sun's energy, as shown by sunspot activity, fluctuates in a cyclic way.
Evidence from nearshore seabottom core samples indicate that at least 17 “ice ages” have occurred during the past two million years. During the most recent one, alpine glaciers much larger than these flowed down from the mountains surrounding the Salish Sea. Moving at a rate of up to a mile every ten years, the glacial fronts advanced far down into the lowlands, widening many of the V shaped river valleys below us into classic U shaped glacial valleys. At the lowland ends of these valley glaciers, where melting eventually matched the foreward thrust, the ice front dropped long piles of rock debris (terminal moraines) as evidence of their massive presence.
Ironically, the alpine glaciers were already in full retreat, far back up into the mountains, when a great ice sheet began its invasion from the north...
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