On the Rocks

Topic: “The View From Below: Using Dike-Wallrock Interactions to Estimate Eruption Rates of the Columbia River Flood Basalts”

By Dr. Heather L. Petcovic

2004-2005 MBGS Officers

The Executive Committee meeting minutes are available on the website.

PRESIDENT: DR. MICHAEL GRAMMER, WMU GEOLOGY DEPARTMENT Ph: 269-387-3667, fax 269-387-5513

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VICE PRESIDENT: DR. ROBB GILLESPIE, WMU GEOLOGY DEPARTMENT, Ph: 269-378-5354, fax 269-387-5513

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MICHIGAN BASIN GEOLOGICAL

SOCIETY PUBLICATIONS

Historical CD #1: Nine out-of-print publications from 1949 through 1965 and 1998, Devonian to Silurian Rock Fieldtrips to MI, WI, IL and Ontario, 2000, $15

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The View from Below: Using Dike-Wallrock Interactions to Estimate Eruption Rates of the Columbia River Flood Basalts

Heather L. Petcovic

Abstract: During the mid-Miocene, vast amounts of basaltic lava were erupted from fissures and vents in eastern Washington, northeastern Oregon, and western Idaho. These flows make up the Columbia River Basalt Group (CRBG), which is currently recognized as the earth’s youngest and smallest large igneous province. The CRBG also includes some of the earth’s largest individual lava flows, many of which exceed 2,500 km³ in volume and traveled over 750 km from their sources. Feeder dikes to many of these large-volume flows are exposed in the Wallowa Mountains of northeastern Oregon. Most dikes are chilled against their wallrock; however, rare dikes caused their wallrock to undergo partial melting. Wallrock melting reactions record the thermal history of basalt flowing through the dike and, consequently, can be used to determine surface eruption history. Partially melted wallrock adjacent to a feeder dike of the large-volume Wapshilla Ridge flow was examined in detail. Results of thermal modeling constrained by this field example suggest that basalt flowed through this dike for 3-4 years. This dike likely represents an upper-crustal (~2 km paleodepth) exposure of a long-lived point source in the CRBG, possibly analogous to the central vent phase of a Hawaiian-style eruption. Based on the thermal modeling results, eruption rates for the Wapshilla Ridge flow ranged from 3.4 to 4.6 km³/day, about 10 times greater than the largest historical basalt eruption and 1,000 times greater than the ongoing eruption at Kiluaea volcano. Atmospheric loading of CO2 during this and other CRBG eruptions may have led to the Neogene global cooling event.

Biography: Dr. Petcovic discovered geology as an undergraduate at Smith College (Northampton, Massachusetts), graduating in 1995. Her undergraduate honors thesis research led her to the Oregon Cascades, where she mapped and analyzed Quaternary lava flows near Mt. McLoughlan and Crater Lake. After graduation, she was an intern with the USGS Water Resources Division in Boston, Massachusetts, and worked briefly in environmental consulting. She returned to the Pacific Northwest for graduate work at Oregon State University (Corvallis, Oregon), where she earned her M.S. in 2000 and her Ph.D. in June, 2004. While engaged in her dissertation research on the flood basalts, she also was awarded an NSF GK-12 Teaching Fellowship and spent a year working with an urban 6^th grade classroom. Since this time, she has worked with Oregon State University’s outreach efforts to urban public school teachers and students. She joined the faculty at Western Michigan University in August, 2004 with a joint appointment in the Geosciences Department and the Mallinson Institute for Science Education. Her research currently involves the preparation of Earth Science teachers, and aspects of teaching and learning geology.

Michigan Chapter American Institute of Professional Geologists

Michael Johnston

Michigan Manufactures perspective on current and pending environmental regulation in MichiganLocation: Sheraton Lansing Hotel, 925 Creyts Road, Lansing, 48917. Directions: On I496 to Creyts Road (exit #1). Turn north on Creyts Road; turn right (east) at first light(Anacapri Blvd.) The Sheraton is the second drive on the right). . Cost: Students $ 25.00, Members $ 35.00, Non-members $ 40.00 Dinner: Buffet Contact Scott Cesarz at (248) 596-1170 or cesarzs@superiorenvironmental.com with reservations no later than December 3, 2004 Mr. Michael Johnston, the director of regulatory affairs for the Michigan ManufacturersAssociation (MMA). As director of regulatory affairs for MMA, Johnston is responsible for advocacy to state regulatory agencies and the legislature in the areas of air and water quality, solid and hazardous waste, wetlands, economic growth issues and electric industry restructuring. In addition to testifying on behalf of the manufacturing industry, Johnston leads several MMA member policy committees, including the MMA Air Quality, Water Quality and Environmental Quality Advisory Committees. Johnston has extensive experience in state government and the legislative process. He served as director of Republican Programs and Research in the Michigan House of Representatives under both Speaker Paul Hillegonds and Republican Leader Ken Sikkema. Johnston started his work in the legislature in 1991, on the Programs and Research staff, as a policy advisor to the Business and Finance Committee. Among several other committee assignments, he served as lead staff person on the re-write of Michigan’s Air Act. Prior to that post, Johnston served in the Michigan Department of Commerce and worked as an environmental ombudsman in the Office of the Michigan Business Ombudsman. He joined MMA in 1999. Johnston holds a bachelor’s degree in philosophy from the University of Michigan.