Hotlum cone, which forms the summit and the north and northwestern slopes of Mount Shasta, may overlap Shastina in age, but most of the Hotlum cone is probably younger. Many of the features of the cone appear to have formed after the retreat of large glaciers from Mount Shasta, which occurred about 6,000 years ago. Early eruptions produced andesite lava flows to the north and east. As the summit dome grew later, explosive eruptions ejected gray lithic tephra across the northern flank of the volcano.
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