OCGC Seminar - Dr. Patricia Manley

Prehistoric earthquake-triggered slumping in Lake Champlain 

Dr. Patricia Manley 
Association for Women Geoscientists distinguished lecturer 
Department of Geology, Middlebury College 



Thursday, January 29th, 2015
9:30 a.m.  

Gamble Hall
Geological Survey of Canada
615 Booth Street



High-resolution CHIRP (compressed high intensity radar pulse) seismic reflection profiles reveal the presence of a deep-water lacustrine slump located in the Main Lake of Lake Champlain. Named the Four Brothers Slump, this slump is composed of a heavily disturbed sediment body that was transported down slope in a mass-wasting event. Seismic reflection profiles data show the slump initiated on a structural rise to the southeast of the slumped area. The Four Brothers Slump has an aerial distribution of 5.5x105 m2 and the volume of sediment transported is 4.8x106 m3. Analysis of the seismic profiles and core material show that the slump failed above marine Champlain Sea sediments near the transition to Lake Champlain sediments. The water-saturated sediments over impenetrable Champlain Sea clays may have led to pore pressure that exceeded the hydrostatic pressure and led to slumping when triggered. Utilizing 137Cs dating and magnetic anisotropy on one of the sediment cores collected, it is estimated that the slump occurred between 3600 and 3800 yr BP and was most likely triggered by a large magnitude seismic event not previously documented.