Deciphering the Dynamics of a Magma Chamber with Microscopic Zircon

June 20, 12:15 p.m., Jackson Senior Center– Open to Public. Presentation: Deciphering the dynamics of a magma chamber with microscopic zircon, Presented by Tiffany Rivera, Westminster College of Salt Lake City

A modern-day super-eruption may potentially result in disastrous effects to the surrounding landscape, decimation of human and animal populations, and global climate change. While modern humans have escaped such a catastrophe (so far), the potential of an impending super-eruption in the United States comes from Yellowstone. Understanding the past eruptive history, including the evolution of the underlying magma chamber, is essential to forecasting any forthcoming doom from Yellowstone. Magma chamber dynamics can be interpreted from chemical, thermometric, and age analyses of the ubiquitous accessory mineral zircon. At Yellowstone, three super-eruptions have occurred in the last ~ 2 Ma; zircon analyses from eruptions associated with magmatism from the two earliest volcanic cycles show similarities in the trend of magmatic evolution and recycling of slightly older material from the plumbing system in the crust. Both the 2.1 Ma Huckleberry Ridge Tuff and the 1.3 Ma Mesa Falls Tuff resided as an eruptable magma within the upper crust for less than 40,000 years, but the main phase of crystal growth and magma accumulation occurred more rapidly – on timescales of 10,000 years or less. However, the Mesa Falls Tuff magma also appears to have tapped a mostly solidified, unerupted, earlier formed magma batch, unrelated to the Huckleberry Ridge Tuff, as evidenced by the distribution of compositions and ages of the zircon grains. This signifies that pulses of magmatism that occurred prior to assembly of the magma feeding the super-eruption, thus allowing for timescales of magma recharge to be determined. The Huckleberry Ridge Tuff lacks this phenomena, but was an order of magnitude more voluminous than the Mesa Falls Tuff. Thus, it is possible that the remaining volume of Mesa Falls Tuff magma remains stored as a solid below the surface of eastern Idaho. If so, could re-melting of the solidified silicic magma result in another super-eruption?