Around 140,000 years ago, glaciers flowed south, carving out the valleys around Ovando, in northern SouthWest Montana. As the Bull Lake Ice Age ended, the glaciers retreated from the area. During the Pinedale Ice Age, between 60,000 and 15,000 years ago, ice covered the region once again. Glaciers again moved into the Ovando/Helmville area, carrying with them rocks and debris-called glacial till-from further north. As the glaciers melted, around 15,000 years ago, they left behind mounds of debris. We can still see these piles of debris-called moraines-in the steep hills around Ovando. The places between the moraines filled with glacial water, forming the area’s many lakes, ponds and wetlands. Some of the ice got buried under till. When these chunks of ice finally melted, the till sank, causing large depressions, called kettles. These powerful glaciers also carved the towering cliffs and high peaks of the Scapegoat and Bob Marshall Wilderness Areas. Not all of the debris got deposited in kettles and moraines. As they melted, huge streams of meltwater carried sand, mud and gravel to the east and north, creating the fertile valleys along the Blackfoot and Clearwater Rivers.
As you travel through Southwest Montana, especially around Montana Highway 200, you can see glaciers’ footprints all over the region, building mountains and carving valleys. If you know what you are looking for, you can follow the Ice Ages’ movements through Montana. For more information, visit the Montana Department of Transportation’s geomarkers page, or drive along Highway 200, and look for the tell-tale signs.
Moraines and Mountains west of Ovando on Highway 200
Tags: geology, intro science, highway markers, roadtrips, Ovando, Helmville