Friday, March 5, 2010

Where in the West: Matanuska River, AK

The terraces on the Matanuska River, Alaska, (mentioned toward the end of my last post) can be seen at and near the Matunuska Glacier. These photos, shown from the glacier and then west along the river towards Palmer, were actually taken in reverse order during that late February day back in 2007; that's why the sun angle changes in the wrong direction in this photo sequence. All locations are shown on the embedded map below.

The first photo was taken from Long Rifle Lodge, looking almost due south, with the glacier just out of the view to the east (left).
This second photo looks about southwest toward Monument Creek, where you can see some of the craggy peaks of the Chugach Mountains and some of the terraces along the south side of the Matanuska River.
At an overlook above Long Lake, I took this zoom photo of some hilly, lumpy-looking terrain north of the river. I'm not sure what these landforms should be called - they appear to be linear in Google Earth.
Matanuska River terraces looking southeast up Coal Creek.
A closer veiw of some of the lower terraces right along and above the Matanuska River, looking southeast, in the early-afternoon shadow of Pinnacle Mountain.
And finally, we arrive back at our starting point (well, this is where my photos of the Matanuska River started, a little after noon). This is an official pullout on the Glenn Highway, just north of Palmer, overlooking the braided and sometimes frozen Matanuska River. This view looks back upriver to the northeast to east toward the Matanuska Glacier, which can't be seen in the very far distance. The pullout is on one of the terraces above the river; Palmer is on what is referred to as Palmer Terrace.
Looking due east across the icy river, this shot shows the six or seven Holocene terraces above river level.
I couldn't climb down onto the loess and dune deposits on the slope below the pullout because of overhung snow, although I did once during a 1997 UAA field trip. The upper sand and silt beds overlie bedded, cobbly river deposits, which overlie poorly sorted cobbly till.
Looking to the southeast from this same overlook, you look downstream along the Matanuska River. Beyond a southward bend in the Matanuska River, you are looking up the Knik River drainage. The Knik River is a wide braided river coming off the Knik Glacier on the eastern arm of this major draingae and the Cloudy and Lake George Glaciers on the southern arm of the drainage. That's probably Pioneer Peak in the distance on the far right of the photo.

I was told while on the UAA field trip not to camp down at river level or on any of the gravelly islands out in the braided rivers. The water level in glacial meltwater rivers rises and falls with a diurnal cycle. The glaciers upstream melt during the day, causing higher flow levels. With nightly cooling, river flow diminishes, and the rivers dump their bedload. The next day, the rivers will use different channels, and if you've left your tent on one gravelly area, you might come back (or wake up) to find it in one of the channels, or flowing downstream with the river.

View Matanuska River in a larger map

References and Links:
Alaska Glaciers Case Study

R&M Consultants, 2005, Glennallen to Palmer Spur Line Soils Studies, Volume 1 of 2, Main Report: Alaska Natural Gas Development Authority (ANGDA). See Section 2.0 Regional Studies, p. 8-20.

Williams, J.R., and Ferrians, O.J., Jr., 1961, Late Wisconsin and Recent history of the Matanuska Glacier, Alaska: Arctic, v. 14, no. 2, p. 82–90.


Dan McShane said...

Thanks for the trip.

Cannibal Panda said...

Gorgeous pictures! Looks like perfect weather. It's fur rondy time there isn't it? Thanks for the pictures and tour- next best thing to being there :)

Silver Fox said...

Dan, glad you enjoyed it!

Silver Fox said...

CP, it's Fur Rondy time, and the Iditarod started over the weekend. It's very snowy right now, yesterday's glacier picture showed only snow.