November 9, 2011

Waterloo Technical Society

Cedar Falls Clarion Inn

Iowa's Manson Impact Structure

Abstract: Seventy-four million

years ago, near the end of the Cretaceous Period, central Iowa lay near the shoreline of an inland seaway that separated eastern North America from rapidly rising mountains to the west. The low-lying Iowa landscape was home to a rich and varied population of plants and animals, including dinosaurs and small mammals. These organisms lived in a fern-rich, mixed conifer and deciduous forest with a warm, moist climate much like today’s Gulf Coast. The environment dramatically changed when a stony meteorite, over one mile in diameter, weighing about 10 billion tons and traveling about 45,000 miles per hour, blasted through the atmosphere and crashed to earth. In the fraction of a second that it took the meteorite to penetrate about one mile into the ground its potential energy was transformed to kinetic energy, the equivalent of about 10 trillion tons of TNT. An electromagnetic pulse moved away from the point of impact at nearly the speed of light, and instantly ignited anything that would burn within approximately 130 miles of the impact (most of Iowa). The shock wave toppled trees up to 300 miles away (Chicago, Minneapolis, and St. Louis), and probably killed most animals within about 650 miles (Detroit and Denver). The blast left a crater over 24 miles in diameter centered in an area of unimaginable death and destruction. Today there is no surface expression of the crater that exists 100 to 300 feet below the town of Manson (Calhoun County), which lies near the center of the crater that bears its na me.

Speaker: Ray Anderson is a Senior Research Geologist with the Iowa Geological and Water Survey in Iowa City, a bureau of the Iowa Department of Natural Resources. He has been a geologist for t he Surv ey for over 40 years. He has studied almost every aspect of Iowa’s geology, but has specialized in our oldest rock s, the Precambrian, as well as meteorites and impact structures, and the Jurassic of Iowa including the Fort Dodg e gypsum deposits. He is active in the Iowa Academy of Science where he has served as the President and on the Board of Directors. Ray has well over 100 publications and professional presentations on numerous geologic features in Iowa, and has organized and produced about 30 geologic field trips for the Survey and the Geological Society of Iowa. Ray also serves as an Adjunct Associate Professor in Geology at the University of Iowa Department of Geoscience.

Program Chair: Gary Dorhout

Time: 6:00-6:30pm Social

6:30-7:15 Dinner

7:15-8:15 Presentation

Location: Cedar Falls Clarion Inn, Cedar Falls, Iowa

Price for meal: $14.00 per person (includes tax, tip & room rent)

Time: Social period: 6:00 P.M. Dinner: 6:30 P.M. at River City Bistro Restaurant, Cedar Falls Holiday Inn, (Clarion Inn) 5826 University Ave., Cedar Falls 50613.

Dinner Reservations: Please contact Jim Garrett via phone 319-233-3052 or E-Mail or Gary Dorhout at by 4:00 PM Monday 7 Nov 2011. Leave name and message on answering machine. Guests are welcome, please be sure to make a reservation.

Dues: Dues of $10.00 may be sent to the Treasurer, Kenneth Friend, 1112 W. 4th St., Cedar Falls, Iowa 50613-2430 (ph 319-277-2312) or paid at the meeting. E-mail