WHAT IS THE FOOTHILLS ERRATICS TRAIN?

A glacial erratic or simply, an erratic, is a rock that is out of place and became so because it was transported by a glacier from its original location and deposited upon dissimilar bedrock. The Foothills erratics are hard and resistant grey to pink pebbly quartzite. Their source is half a billion year old rocks in the Main Ranges of the Rocky Mountains in Jasper National Park. They commonly rest on less resistant sandstone or mudstone formations that underlie the Foothills. The bedrock of the Foothills is one-fifth the age of the quartzite.

Where similar types of erratics are found to be distributed in a linear or ribbon-like pattern, they are referred to as an erratics train.

An example of the linear distribution of Foothills Erratics along the east side of Porcupine Hills
near Willow Creek. Arrows indicate distant erratics. Note people near erratic for scale

The Foothills erratics train of Alberta can be traced more than 580 km along the eastern edge of the Rocky Mountain Foothills from McLeod River in the north to the international border in the south.

Generalized flow directions of glaciers covering Alberta
during the last ice age called the 'Late Wisconsinan Glaciation'.

It is composed of thousands of quartzite and pebbly quartzite blocks between 1 m and 41 m in length. Erratics near Okotoks, Airdrie, and Glenwoodville are the largest. The erratics train documents the last and apparently the only coalescence of glaciers originating in the Rocky Mountains with the southwestern margin of an ice sheet that mantled much of North American continent.

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