About the East Moraine

{child_byline}Ellen Morris Bishop

Wallowa County Chieftain{/child_byline}

Sidebar: About the Wallowa Lake Moraines.

The moraines of Wallowa Lake are among the most accessible and best preserved glacial moraine features of the Ice Age in North America. Their preservation from further development is critical to ongoing and future research about the Ice Age, and the geologic history of the Northwest.

About 20,000 years ago, the area we know as Wallowa Lake was a mass of moving, grinding, groaning glacial that towered more than 100 feet above the barren gravel deposits that we know today as the moraines of Wallowa Lake.) A ‘moraine” is a deposit of gravels and large rocks known as “erratic” that have been eroded by glaciers and deposited as the ice moves or melts. The moraines along the sides of Wallowa Lake are “lateral” moraines. The lower moraines at the north end of the lake, including most of Iwetemlaykin Natural Area, are “terminal” moraines—gravels deposited at the front of the glacier as the ice there melted.

Cosmogenic dates that tell how long a freshly polished rock has been exposed to the sun indicate that both the east and west moraines were barren pole of gravel in the final stages of formation about 19,000 years ago. The spectacular moraines are among the best-preserved and certainly most accessible Late Pleistocene (Ice Age) glacial features in North America, and rank high on the scale of such features globally. They are important because of their aesthetics and habitat, and they also preserve geologic records of Pleistocene glaciation and climates.

To the east of the young, steep-sided East Moraine, the corrugated landscape includes older moraines that record the gradual erosion and unroofing of the Wallowa Mountains over perhaps the past 1.5 to 2 million years. The geologic history of this larger Ice Age landscape is currently a research project of the University of Oregon geology field camp. By examining the rocks in these moraines, geologists can begin to craft a picture of what the Wallowa Mountains might have looked like 2 million years ago. The older moraines may also preserve pollen and other clues to past climate and vegetation.

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