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TERRY PAVLIS: There's a group here
that's involved in a study called the Saint Elias Erosion
and Tectonics Project.
It has the acronym of steep.
As the name implies, it's a study
that emphasizes the interactions between tectonic processes,
which are interior motions of the earth and surface
processes of erosion to form mountain systems.
The Saint Elias mountain ranges in Southern Alaska
are right in the corner of Alaska.
And it's characterized by extreme topographic reliefs,
with elevations top out at 18,000 to 20,000 feet.
Most people in North America probably can't even
find this place on a map, and yet it's
North America's greatest mountain range.
The feature that makes this area particularly significant,
and the reason we're actually here in the STEEP project,
is that there's a unique interaction here
between erosion and tectonics.
Tectonics acts to build the mountains and erosion
acts to destroy them.
And in this region, both of those processes
occur at a extremely high rate relative to many other parts
of the world.
We're sitting in a unique climatic setting
at a high latitude in the North Pacific.
And strong North Pacific storms pound this coastline
every winter and drop very large quantities
of snow, a hundred feet or more in many
of the high mountain regions.
And those can accumulate over time
to produce glacial ice, which represent
by most people estimates the most aggressive erosion
agents on the planet.
And so we're looking at that particular interaction, which
we have with glacial systems and a very active tectonic system,
to build this particular mountain range.
As we check the Karr Hills, we'll
see whether there's a landing spot or there's
anything you can sample there.
And then maybe throw people on the boat for part of the trip
back so we just have one backup.
The effect of that landscape that
has been reshaped by glaciers has
been that deformation patterns have shifted over time,
so that fault systems that were active
a million years ago shut down.
And we have new faults that have activated in different places.
And so one of our goals here is to understand
how those systems turn on and off,
and why they turn on and off when they did.
My team is part of the structural geology group.
Our job is to look at the long-term development of faults
and folds of the rock masses.
SPEAKER 1: Yeah, if you look in the rock in here, guys,
look, you can see there's sort of a scaly fabric.
A lot of it is parallel with the fault zone.
TERRY PAVLIS: This is just one of innumerable faults
that are in this region.
We would just go systematically and work our way
through this region, describing the faults
and determining their geometry and looking
at which stratigraphic units are sitting
on either side of the fault, because that
allows us to get more information about how
much they've moved.
And that allows us ultimately to reconstruct
the motions that occurred in the construction of the mountains
here.
JULIE ELLIOT: Well, a lot of the geology that they're looking at
tells you about the motions that have happened in this area
during the past.
And the GPS tells you the motions
that are happening right now at this instant.
So first of all, it'll tell us how the tectonic plates
in this area are moving.
And then with that data I'll be able to constrain
where possible faults are and how much motion there
might be on those faults.
TERRY PAVLIS: So we see a tectonic process here
in which motion on those faults is acting
to produce the mountains.
The other part of the story that's
right here in front of us-- we see a glacier
that's actively carving out the landscape
and dumping sediments down this fjord.
That process has been acting on this mountain
range for at least five million years.
And that interaction of how those come together
is sort of the central theme of this particular project.
KEN RIDGWAY: We're going to go up on the west side of Icy Bay
to look at the Yakataga Formation.
Some people think it's as old as 15 million years.
But most people think it's about five million years.
And it really marks the start of sedimentation
from the glaciers, so we're going
to go in that glacial-derived material in the rock record
out in front of the mountain belt.
We're going to take a look at these rocks straight ahead,
see what's on the back side.
But then we'll curve along the point
just to see some of the deep glaciated areas
where we might be able to work.
SPEAKER 2: That one is ready for a label.
KEN RIDGWAY: Well, this is an interesting exposure
because these are rocks that are probably
about three million years old.
So you can see all these white spots, these are a clast.
So these were pieces of rock that
were carried by the glacier, were entrained into the ice,
and came out on icebergs.
And they drop down into this brown unit, which was soft mud.
And so even if we don't know everything about the mountains,
we have this package of sediment that's out in front of them.
And we know the oldest sediment that was eroded off
is at the bottom.
The youngest is at the top.
And then we can start to date things in between
and look at the fossils to know how old, when did it start,
was there more sediment at one time.
RACHEL HEADLEY: Well, I'm studying
the speed of the glacier for use as a measurement of what
the erosion rate might be as part of the Saint Elias Erosion
Tectonics Project.
What I've done is I've put different targets out
on the glacier surface on a longitudinal profile
and also a transect so that I can
get what's happening, how the velocity changes
as I go across the glacier.
And I'm using this theodolite, which
is a surveying tool, to measure the angle change
over a period of six days.
So basically, the more the angle changes over
that period, the faster it's going.
What we're interested in specifically
is looking at, if the glacier is carving down really fast,
what does that mean in terms of the uplift of the mountain
itself.
Does it mean that the glacier will just carve down?
Does it mean that because the glacier is carving down
it's actually thinning the crust and making it slightly lighter,
so maybe it will uplift a little faster because it's lighter?
We're interested in looking at those kind of interactions.
My work is definitely one piece of a larger project.
We have people looking at all the different facets that
make this mountain region.
And so it's definitely a very complicated puzzle.
But all the pieces do fit in.
TERRY PAVLIS: There are some things we already
know from the field work.
It's pretty clear what some of the map pattern relationships
are, the geometry, the structures,
which we've been working on here for the last few days.
A lot of other things we'll have to take back
to the lab for doing dating techniques
and various other things.
So there's lot of work left to do, but this is the hard part--
fun part, too.
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