Dennis O’Leary of Ouray, Colorado passed away suddenly on October 27 at Montrose Memorial Hospital. He was born in Cambridge, Massachusetts to William and Gladys O’Leary and is survived by his loving wife Christina (Claussen) O’Leary of Ouray, daughters Rosanne (Steven) Fischer of Loveland, Colorado, Celeste (David Fourtner) O’Leary of El Paso, Texas, four grandchildren, and sister June (Charles) Cottuli of Marshfield, Massachusetts. He received his B.S. degree from Boston College, M.S. from Missouri School of Mines, and PhD. From Penn State University, all in Geology. He spent 38 years working for the U.S. Geological Survey and retired to Ouray in 2010 where he enjoyed hiking and observing the geology of the area. He continued writing geological articles until his death. A true Renaissance man, he loved art, music, history, and current events, but his greatest love was for his family. A private memorial will be held at a later date.