James V. O'Connor, 55, the former geologist for the District of Columbia who made it his calling to educate people about the physical world around them, died Nov. 5 at his home in Kensington. He had esophageal cancer.

Mr. O'Connor, who was born in the Boston area, was a graduate of Boston College where he also received a master's degree in teaching. He came to the Washington area in 1970 for further study at the University of Maryland.

He was an instructor at Maryland before joining the U.S. Geological Survey, where he worked from 1972 to 1981. He was a physical scientist and national coordinator for a program to encourage more minorities to become earth scientists.

In 1976, Mr. O'Connor began teaching geology at the University of the District of Columbia, a career that lasted until 1997 when he was laid off as an associate professor of geoscience, along with scores of others, as part of a cost-cutting measure. After that, he became a lecturer or adjunct professor at American University, Catholic University and George Washington University. In 1998, he was hired by the D.C. Department of Health as an environmental specialist in hydrogeology.

During his career at UDC, Mr. O'Connor also served as the official "state geologist" for the District, providing expertise to city officials and residents on problems such as a series of slow-moving landslides that damaged property in Southeast Washington. Mr. O'Connor trained for the Jesuit priesthood before deciding to become a scientist, and believed that his true calling was to instill in others the same passion he had for the natural world, especially its geology.

He led more than 300 science education workshops, and wrote dozens of course manuals and geologic guidebooks, many focusing on using the local environment as an outdoor classroom. Most District public school teachers have taken a class or tour with him, and he also held workshops for children at several D.C. public housing projects.

For years, he led tours for the Smithsonian Resident Associates; he also taught classes at the Audubon Naturalist Society and U.S. Department of Agriculture Graduate School. On his walking tours, Mr. O'Connor would point out fossils in building stones as well as paved-over features of the physical world, such as a former stream valley in downtown Washington. He could talk knowledgeably about street trees, city history and architecture as well.

"You don't have to go very far to see some neat stuff," he told a group of science teachers in June during a two-hour tour that covered only one city block because he had so much to show them. "Cities can be fun and it doesn't cost anything."

Mr. O'Connor was a past president of both the National Marine Educators Association and the eastern section of the National Association of Geoscience Teachers. He was president of the D.C. Environmental Education Consortium. He had served on the boards of the Audubon Naturalist Society and Discovery Creek Children's Museum, and on the editorial board of the Journal of Marine Education.

He was a member of Saint John the Evangelist Catholic Church in Silver Spring.

His marriage to Mary O'Connor ended in divorce.

Survivors include his wife, Rosanne, and their daughter, Maryann O'Connor, both of Kensington; his mother, Mary O'Connor, of Somerville, Mass.; two brothers, John O'Connor, of Brockton, Mass., and Justin O'Connor, of Asheville, N.C.; and a sister, Janice Ronalter, of Newton, Mass.