Science Workshop: November 7, 2014. 1 PM. Dickinson 232.
Volcanoes spend most of their existence not erupting. This doesn’t mean that there aren’t a multitude of magmatic processes going on underneath. These might include intrusions of new magma, crystallization of existing magma, magma mixing and movement of crystals through the “crystal mush” that sits under the volcano. These processes all leave their compositional and temporal signature on the crystals that form and are subsequently incorporated into the magma that does erupt. I will discuss how examination of zircon crystals in magma can help us unravel the timing and nature of events that occur between volcanic eruptions with a focus on the evolution of the Lassen Volcanic Center in California. Overall, current trace element and U-Th disequilibria age data derived from zircon suggests that an otherwise moribund magmatic system can be brought back to life (rejuvenated) by new intrusions of magmatic that are geologically ephemeral, lasting years to millennia. This conclusion means that the events that lead to the 1915 eruption at Lassen Peak unfolded rapidly before the explosive eruption, the only to occur in California in the last century.