Rockin' in the Valley

July 25, 2006

OUT AND ABOUT/Mary Ames

For a rock collector such as myself, the Mat-Su valleys are a sweet slice of heaven. Glaciers carved the Matanuska Valley and the wide Susitna plain. As the glaciers advanced, they carried rocks from the mountains, ground rocks within their ice casings, and tumbled rocks in their melt water. As the glaciers retreated, they dropped lots of rocks.

Two major glaciers, the Matanuska and the Knik, still are quite visible, but the tracks of long-gone glaciers are easy to spot, too.

Glaciers create U-shaped valleys through mountains. You can scan the Valley and see where glaciers have been. From the west side of the Palmer Hay Flats, for example, you can see where Eklutna Glacier poured out of the Chugach Mountains. Cirques, concave basins on the side of a mountain, are left behind by glaciers when they melt. Sometimes, too, a high-mountain lake remains.

And almost anytime you take your feet off the pavement here in the Mat-Su, you'll see the left-behind rocks. These mountains around us are newish, geologically speaking. As the mountains erode and get worn away by weather and gravity, rocks begin to roll down to the valley below. Gravity brings some rocks to rest on the valley floor, while rivers bring in others.

This Valley has got some rocks.

Once upon a time, about 2 to 3 million years ago, snowfalls from the moist Pacific winds cooled against the mountains and formed layer upon layer of snow, creating glaciers that moved down the mountains, grinding everything in their paths. Glaciers advanced and retreated about four times in those millions of years. When the glaciers were at their zenith, ice sheets covered the Pacific Coast Ranges completely. In periods of glacial warmth, forests flourished and animals thrived. The last ice-sheet retreat happened about 10,000 to 12,000 years ago. That's book learning from a tome called &#8220Geography and Geology of

Alaska.”

The book's authors, Leo Mark Anthony and A. Tom Tunley, call our area an Intermontagne Trough. The southern half of the trough is submerged in Cook Inlet, and the Talkeetna Mountains dissect the trough as it runs north. The Susitna River rises in this trough in the Alaska Range, and it's joined by the Yentna, Talkeetna and Skwentna rivers as it flows south. The Susitna carries &#8220hundreds of thousands of tons of sediment to the sea daily,” they say. But all those rivers leave rocks behind, too.

Telling people about your favorite rock-picking area, in my book, is akin to telling them about your favorite fishing hole, trapping area, or hunting ground. Those just aren't things you share with the world at large. But the Valley is so big, so filled with rocks, that pointing out some obvious places won't deplete the resource.

The Matanuska River, just outside of Palmer on the Old Glenn Highway, has some of the best rock-picking around and is readily accessible. You can park nearby when the water is high, and when the river is low, some people drive out on the gravel bars. Generally speaking, river waters rise when hot summer days melt the glaciers, and when it rains.

I love to go bar hopping on rivers, traveling from one gravel bar to the next, wading across ice-cold pools or shallow riffles. This is one way you can bar hop for hours and never feel ill the next day. High water limits bar hopping, but it brings new rocks and driftwood to the bars that will emerge, reshaped, when the waters ebb.

We go collecting rocks, my chums and I. Sometimes, we go on a specific mission. All flat rocks today, we might say. And we go out looking for flat rocks to build a pathway. But even when we're on a mission, we're selective. We don't pick just any flat rocks. We pick rocks that suit our fancies. When we want rocks that are mostly green or red, we stick with the Matanuska River.

When we want black-and-white rocks or rocks with orange intrusions, we head for a branch of the Knik River. We don't go where campers and ATVs flock on the massive flats off the Old Glenn Highway. We go off the Old Knik Road. With Pioneer Peak and the Chugach looming above us, and the bars stretching out in a broad fan, the sense of being diminished by our surroundings is strong.

We don't collect rocks like true rock hounds would. We pick up only the rocks that call to us or look intriguing. Some rocks, you just want to pick up, to feel the grain and weigh the heft as you balance it in your hand.

What I like best is knowing I am holding something that was formed millions of years ago, or maybe only a few hundred thousand years. I like speculating on the forces that eroded a rock into its current shape. When I think of the tremendous forces of heat and pressure than turned solid rock into a liquid intrusion, pressed dust and sand into solid rock or pressed dissimilar grains and pebbles into a conglomerate rock, my brain kinda boggles.

Our method of picking rocks and driftwood is to gather our favorites into small piles as we work our way out on a river bar. When we have gotten as far as we want to go, we start bagging the rocks and head back. This way, we know how much work we have, how much weight we have to carry, how many trips we have to make back and forth.

One hot summer day a few years ago, after hauling several bags of rocks to the truck, I realized how few people get to do what we were doing.

Most people who haul rocks in the hot sun have been convicted of doing some really naughty things, I said. We laughed, drank some water and returned to our task, with no one forcing us to do so. We use these rocks for raised garden beds, for walkways and for yard art statements. Their forms dictate their function for us. I feng-shui rocks around my bathtub and on my living room floor.

Gems are OK, and precious metals are fine in their own way. But I have always been more fascinated by the surrounding rocks than by those minerals and metals that are so precious to others. I like the quartz more than the vein of gold that runs through it.

Rocks tell tales of time.

Contact Mary Ames at

352-2284 or mary.ames@

frontiersman.com.