Igneous Intrusion

Provided by: Kent Barnes
Summary author: Kent Barnes

The above photo along a road-cut, near Cascade, Montana, shows an igneous intrusion in sedimentary rock. The intrusion (dike) approached from the left, turned close to horizontal along a bedding plane and then angled toward the peak. Igneous intrusions are more resistant to erosion than are sedimentary rocks, which results is the triangular-shaped hill.

Related Links:

• Montana Department of Transportation
• Igneous Intrusions
• Geology of the Sideling Hill Road Cut
• Roadside Geology of Montana

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