UPDATE: ONLINE Lecture: The Role of Snowball Earth Events in Bedrock Weathering

***UPDATE: Due to the unrest caused by the overwhelming ICE presence in the Twin Cities and the frigid temperatures predicted for Monday evening (albeit much warmer than now!), it has been decided to MOVE Monday's lecture to Zoom.***

Presenter: Mark Jirsa, M.Sc., Minnesota Geological Survey (retired)

Link to Presenter: https://www.researchgate.net/profile/Mark-Jirsa

Full Title of Lecture: The Role of Snowball Earth Events in Bedrock Weathering

Summary: The landscapes we enjoy today are the product of two opposing forces:

1. Continental plate collisions that raise land surfaces (to mountains in some cases)

2. Chemical weathering and erosion that removes literally miles of uplifted bedrock

Thus, we stand on bedrock outcrops that were once deeply buried, metamorphosed, deformed, weathered, and eroded.

(Whether this lecture will or won't be recorded for GSM's YouTube Channel is yet to be determined.)

Biography: I grew up in the “wilds” of northern Wisconsin: an area of lakes, rivers, and woods. This uniquely prepared me for a 45-year long career of geologic mapping, primarily of Precambrian bedrock in the wilds of Minnesota and parts of Canada. I attended Graduate School at UMD (1976-1979). In 1976 I worked with John Green mapping along Lake Superior shorelines and inland for the Coastal Zone Management Program to address impacts of shoreline erosion due to then rising water levels. Having fallen in love with the North Shore, I created a thesis using interflow sedimentary rocks to develop a tectonic model of western Lake Superior. After graduating UMD, I worked briefly for Exxon Minerals in NW Mn and Wisconsin. Thanks to G. B. Morey and Dave Southwick, I was hired by the Minnesota Geologic Survey in 1979. I authored or coauthored many of the bedrock geologic maps and publications produced by the MGS. I retired during covid in 2021. I continue to work with the Institute on Lake Superior Geology, and give lectures to small groups.

Virtual Lecture Registration Info: Online virtual lectures require free registration for those who are not dues-paying GSM members; dues-paying GSM members have just received an e-mail with the link and participation instructions. If you are not a dues-paying member of GSM and wish to attend this free lecture online, register by 8 AM CT Monday, January 26 by following the registration instructions posted at this lecture's page of GSM's website.

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