The Butte-Silver Bow Public Archives will continue its Brown Bag Lunch series on Wednesday, May 10, with a presentation by Larry Smith entitled Glacial Lake Missoula and its Giant Floods. The Clark Fork River was dammed during the last ice age by a glacier at the current location of Lake Pend Oreille near the Idaho/Montana border. Between about 20,000 to 14,500 years ago the lake rose and fell multiple times. At its maximum, the lake was 2000 feet deep at the ice dam, 1000 feet deep at Missoula, and extended up the Clark Fork River valley to near Drummond. A record of filling and lowering to the maximum level has recently been described from sediments between Drummond and Bearmouth, along I-90. Dating of the deposits shows that the lake rose and fell to this level about 12 times. Others have inferred that the lake rose and fell 35-90 times, but many of those events possibly did not reach the maximum elevation seen near Drummond.

Larry Smith is an associate professor in the Department of Geological Engineering at Montana Tech. He has been studying glacial Lake Missoula for about 17 years. He got interested in the lake deposits while working at the Montana Bureau of Mines and Geology. He studied the huge gravel deposits in the Alberton Gorge area, which were moved during cataclysmic lake drainages. The gravels host the aquifers that residents use for groundwater. Larry has Bachelor's, Master's, and Ph.D degrees in geology from University of California, Santa Cruz and the University of New Mexico. He has lived in Butte for 23 years.

The presentation will begin at noon and run about an hour at the Archives, 17 W. Quartz. Guests are encouraged to bring a sack lunch. Coffee and water will be provided.

Brown Bag Lunches are held the second and fourth Wednesdays of every month. Upcoming lectures will focus topics of local interest. For more information, contact the Archives at 782-3280.