This cliff in central Montana was formed by two very different events separated by tens of millions of years - a period of volcanism and an ice age. Here, ice age flows of water along the southern margin of the Laurentide Ice Sheet cut into the Shonkin Sag Laccolith, exposing the spectacular cross-section represented by the cliff. Such views of plutonic formations are rare - something normally only seen in textbook diagrams. To learn more click here (site does not open on many mobile devices).
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