Alaska Part 2: More glaciers!

The next main attraction of the trip was the hike on Matanuska glacier, another terrestrial glacier east of Anchorage.  Along the way we stopped for lunch at a place that grilled freshly-caught Alaskan salmon for us out on the back lawn.    The place also conveniently had this fantastic view of the valley and the glacier itself.

The view of Matanuska Glacier from our lunch cookout.
The view of Matanuska Glacier from our lunch cookout.

When a glacier stops moving it continues to melt under the sun but it doesn’t get any fresh ice to replenish the white surface.  That means all the mud and rocks that were previously inside the glacier pile up on top of the glacier, leaving behind what looks like a muddy field.  It mostly looks pretty gross, but in this case enough mud has accumulated for long enough that a young forest has begun to grow on top of the glacier.  The closest section of trees in the picture below is growing on top of the ice, which scientists first noticed when trees collapsed on top of a melting section of ice!

VIew from the terminus of Matanuska Glacier of the mud and forest on top of the ice.
VIew from the terminus of Matanuska Glacier of the mud and forest on top of the ice.

I really couldn’t even tell that the mud we were walking on was only a thin layer on top of the ice.  When we dug down an inch or two through the mud, though, we found nothing but solid ice.  Here is a great example that, if you look closely, shows rocks suspended in the ice.

A close up view of ice revealed under the mud on Matanuska Glacier.
A close up view of ice revealed under the mud on Matanuska Glacier.

The most interesting stuff, though, was the active part of the glacier.  We hiked across the mud to the ice and up a ways until we came to a small lake that has formed from melting ice in the middle of the glacier.  To get a sense for how big the ice forms are, there is a climber on the left side of the picture climbing the face of the ice (again you might have to click on the image to enlarge in order to see the climber).

View of the small lake that has formed in the middle of Matanuska Glacier.
View of the small lake that has formed in the middle of Matanuska Glacier.

The big muddy object in the foreground of this picture is one of the really cool features found on glaciers.  Rocks that are propped up like this are called table rocks and can be found all over the surface of active glaciers.  As the surface of glaciers melt, they leave behind all the rocks and mud contained within.  As the rocks and mud are first exposed to direct sunlight, however, the ice underneath the objects are hidden from the sun and therefore can’t melt as fast as the ice around them, so the objects are propped up on these little mounds of ice.

All the mud and rocks wasn’t what I had pictured when I first imagined hiking on a glacier.  The ice is what makes glaciers so visually stunning.  In lots of place we found this really vibrantly colored blue ice.

Glacier ice melts and re-freezes in bubble-free ice that has this blue hue.
Glacier ice melts and re-freezes in bubble-free ice that has this blue hue.

Some of the ice in a glacier melts and refreezes, and when this happens all the bubbles are squeezed out of the ice.  This denser, bubble-free ice scatters the light differently, giving the ice a beautiful blue hue.  Here we saw a couple layers of the blue ice but one of the layers is partially covered in dirt and rocks.

There was a ton more we saw just on this day, but these were some of the main highlights.  This was probably the best part of the trip for me, when else will I get to walk on a glacier!?

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spacewx

Graduate student at the University of New Hampshire

One thought on “Alaska Part 2: More glaciers!”

  1. Excellent reporting on the wonders of glaciers Bruce! Someday I would enjoy traveling there myself. After writing to you about the northern lights I realized it’s the wrong time of year for viewing, duh. I know you’re enjoying your trip and I’m enjoying reading about it

    Thanks…Reyn

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