Alaska's Glacier Bay is a region still emerging from its long frozen sleep under the ice.
Dark ribbons of broken rock are hauled toward the sea by the grinding glaciers that sculpt
the mountains and remodel the land.
The glaciers bulldoze down the valleys with a harsh weight of a thousand winters.
In the glacier's path, nearly all that existed of life, of plants or animals or man, is swept
away.
Ice grips the land in a deadly embrace, yet the mass of the ice itself is living.
A historical yourself inżebody.
From the
Two hundred years ago, a single great tongue of ice lay in Glacier Bay.
We are still in the midst of an ice age that has seen four major periods of glacial advance
and four retreats.
The pullback of the ice continues today.
The long ice leaves a void, an empty stage for the opening of another ancient drama.
The process of life returning to land just released from its glacial prison.
Even as the ice melts, giving up the barren earth, nature's grand design for the land's
renewal is waiting.
From spores carried on the wind, from seeds in the droppings of birds, from the chemistry
of water, soil and sun, the first forms of new life emerge.
A spot of lichen or a button of moss holding forth on barren rock.
Then the pioneer mountain avans lay down a fertile blanket for the roots of alder, willow,
and cottonwood.
A ground made of simple twisted launched
From the tangle of alder, willow, and cottonwood thickets, young spruces shoulder up toward
the sun.
In the final realization of climax forest, hemlock giants rise above the spruce.
Several thousand years ago, the glacier advanced over an ancient forest.
The climax of an earlier plant succession that reached to the upper bay.
Sand and gravel drifted around the bases of some of the trees before the ice moved over
them.
As the ice began to recede at the mouth of the bay 200 years ago, the stumps of the old
trees were uncovered.
The glaciers are melting, but their decline is fitful.
One finger of the ice may grind forward as another shrinks.
A glacier retreating this year may lunge ahead next, only to fall back at some future time.
A change of two or three degrees in the region's temperature could bring the ice thundering
again to the sea.
No
one knows how many times before life may have flourished here, nor do we know when ice may
claim the bay again.
Glacier Bay is a theater of primal dramas and a reassurance of the continuing triumph
of life on the earth.
How shall we speak of a glacier?
Call it white, and that's forgetting the blue.
Define a glacier as ice, and you're overlooking that it's also rock and it's dripping rushing
water.
Think in terms of the past of a long ago ice age, and you're neglecting the present.
Glacier Bay National Park and Preserve, northwest of Juneau, Alaska, is a place to experience
both present-day ice and landscape created by previous glaciation.
Planks here lift 15,000 feet above the sea.
Their fangs are white, saw-toothed meeting of land and sky.
Glaciers born of these heights reach to tidewater and calve off icebergs.
Climb the slopes beside a glacier, and you're stepping where ice repeatedly is advanced
and retreated.
Reach a high vantage point, and the scene reveals the glacier's true scale.
The ice forms a huge frozen river flowing to the sea, fed from far back in the mountains.
The cliff calving off iceberg seems towering as you float before it, and it does rise more
than 100 feet above the water.
But from the perspective of a high slope, you see the vast ice that nourishes the tremendous
cliff.
Fly up Reed Glacier to the Brady Icefield, and perception of park glaciers changes yet
again.
Here is ice nourished by today's clouds sweeping in from the Pacific and dropping their moisture.
In the Fairweather Range, winter's snowfall is greater than summer's melt.
Fed by flakes falling from clouds and avalanches sliding off surrounding slopes, snow packs
to ice.
Its own pressure causes crystals to deform.
Park flow begins.
The whole glacier creeps down slope in response to gravity.
Viewed moment to moment, this movement is not easily seen.
Time itself seems frozen.
Like a conveyor belt ever moving at barely changing position, the ice may reach sea level.
About 50 glaciers along today's Alaskan coasts enter the sea.
A dozen of these are within the park.
Currently some are lengthening, others shrinking.
The process is unending, the change constant.
Where Glacier Bay whales now swim, there once was ice.
That ice melted, forests flourished, then the ice came again.
Clingit Indian people were forced out of Glacier Bay by advancing ice.
Captain George Vancouver, exploring for England, couldn't get in.
Where cruise ships today enter park waters, Vancouver noted in his log, a compact sheet
of ice as far as the eye could distinguish.
He sailed on.
Today that ice is gone and waterways thread beneath mountain peaks in place of glacier
tongues.
Forests re-close the lower reaches.
Bareness still dominates upper fjords and some glaciers have withdrawn.
Other glaciers in the park, however, are inching forward.
They start among high peaks where their white blankets receive continual renewal.
No Alaskan tidewater glaciers are floating.
Their ice rests on the sea floor.
Advancing or retreating, all glaciers shape the land.
They pluck and rasp and grind the rock they slide over.
Then they deposit what they've quarried.
To mentally picture the dynamics of the ice, visualize first the mountains and the snow
storms.
The snow deepens and compacts to ice.
Pulled by gravity and prompted by its own internal pressures, it begins to move.
The bottom of the glacier rides over whatever lies in its path.
Where bedrock slopes deeply, ice accommodates to the contour by splitting at the surface.
This forms crevasses, some gape a hundred feet deep.
When sufficient snow feeds a glacier, nothing can stop its forward motion.
If jutting bedrock lies in its path, ice will flow over and around.
And we may see a knob smoothly rounded by overriding ice or a peak jagged where it rose
above the ice.
See the polish of rock walls and you're viewing the slow work of ice pushing against its bed.
Or notice scratches.
They're the sandpapering and filing of gravel and rocks frozen into the glacier and dragged
against bedrock.
Where do rock tools originate?
Some are plucked free as the ice inches forward.
They are the rasps that widen and deepen the valley troughs sculpted by glaciers.
Rock rolls and avalanches onto the ice surface and becomes a part of the glacier.
Some rock rides externally as visible ribbons of rubble called moraines.
Some rides unseen part of the internal glacier.
There may be so much rock that the ice turns black and the calving face is striped.
Rock is one ingredient of a glacier in addition to ice.
Flowing water is another.
The water comes from melt trickles and rain runoff.
Lubricated by even a film of such water at its base the glacier slides over its rough
bed.
Water also carries off and deposits material ground from bedrock by the glacier.
Silt so fine it's like flour floats in suspension and turns to sea milky where glacier melt
mixes with salt water.
Fresh water is not as dense as salt water.
It rises to the sea surface and floats blending its glacial silt with the clear sea water
and creating color patterns carried by the currents.
Outwash deposits edge into the sea.
Over time outwash debris pouring from a glacier may fill even huge valleys to great depths.
Today's surface gravels may support dryas and willow and alder and spruce.
Streams cutting down to former surfaces sometimes reveal remnants from forests of long ago.
Ice advancing into salt water mounds up rubble along its margin.
Additional silt, sand, gravel and rocks from tiny to huge fall from the lower end of a
glacier's conveyor belt.
Such debris forms a terminal moraine, a ridge beneath the ice snout.
Glaciers with enough debris to partially fill in ahead of themselves may advance into exceedingly
deep water.
Their moraines protect the ice fronts and reduce erosion.
Without such a shield a glacier could not supply ice to its snout fast enough.
Before ice would melt and break off then can be replenished from above.
The glacier would draw back to shallow water.
This happened to the Lamploo and Reed glaciers.
At low tide it's obvious that their snouts rest on shore.
There they stabilized and now they may again be building underwater moraine and starting
to re-advance.
The Johns Hopkins and Grand Pacific glaciers clearly are advancing.
They carry huge amounts of rock, raw material for a barrier between ice front and sea.
Furthermore the upper ends of all these advancing glaciers lie high enough to be well nourished
by snowfall.
Tidewater glaciers thus are different than those entirely on land.
They respond to climate and also to their own terminal moraines.
Climate controls broad trends but for glaciers reaching the bay the dynamics of advance and
retreat are fine tuned by water depth.
That crucial depth in turn depends on the snout's relation with its moraine.
The shallower the water at the snout the fewer the icebergs calved off.
Those that fall from the crevasse and pinnacle cliff towering above sea level of course are
affected by water depth.
But how much ice breaks off below the surface depends directly on how much of the glacier
is exposed to the water's warmth and erosive action.
Any tidewater glacier that loses the protection of its moraine is doomed.
Present climate can't build the upper glacier fast enough to balance the ice calved from
a snout in deep water.
Ice is buoyant.
Waterbergs rise silently creating undulating waves of ice covered water.
If a tidewater glacier is undernourished by snowfall or in some other way loses grip on
its terminal moraine retreat begins.
With the barrier between ice and sea gone the glacier virtually unzips.
During the last two centuries ice in the main glacier bay waterway is melted back sixty
miles from where Captain Vancouver saw it.
In Muir Inlet more than twenty miles of what was glacier is now fjord.
Few present day glaciers in the park actively thrust forward into the fjords choking waterways.
Most have retreated to the heads of their inlets.
Will today's white scene prevail tomorrow?
No.
Glaciation is a dynamic process.
Snow crystals shower from the sky and compress into ice.
Glaciers inch down slope sculpting the land calving into the sea.
They come and go and come again.
The glacier's story is cyclic ongoing never ending.
Looking up above.