Since the end of the Coast Range Arc about 50 million years ago, many volcanoes have disappeared from erosion. What remains of the Coast Range Arc to this day are granitic intrusions, which were formed when magma intruded and cooled at depth beneath the volcanoes. However, remnants of some volcanoes exist in southwestern Yukon, including Montana Mountain, Mount Nansen, and the Bennett Lake, Mount Skukum and Sifton Range volcanic complexes.