Discussion of magmas coming from depths of 150 km (100 miles) with magma generation in the asthenosphere and ascent through the lithospheric mantle and crust. Plate tectonic models for flat-slab subduction of the Pacific Farallon plate under Central Montana. The Great Falls Tectonic Zone.
Lava flows and radial dike swarms of the Highwood Mountains. Differentiation in the Shonkin
Sag laccolith. Ultramafic fragments of the asthenosphere at Haystack Butte brought up from
depths of 150 km. Shonkin Sag - outflow channel of Glacial Lake Great Falls.
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