George G. Shor Jr., the geophysicist whose studies of the ocean floor helped lay the foundation for the theory of tectonic plates and continental drift, died July 3 at his home in San Diego of complications following a series of strokes. He was 86.

He helped develop the nation's fleet of oceangoing research vessels, was a principal in the abortive Project Mohole near Hawai'i to drill a hole deep into the Earth, and played a key role in creation of the California Sea Grant program, which funds marine and coastal research.

Shor joined Scripps in 1953 at the beginning of what researchers have dubbed the golden age of oceanography, in which research vessels from Scripps, Columbia University, Woods Hole Oceanographic Institution and Cambridge University plied the oceans.

His work and that of others eventually led to the conclusion that the planet's continents reside on massive tectonic plates that are adrift on the ocean of volcanic magma far below the Earth's surface, pulling apart in some areas to create deep trenches in the ocean and jamming together in others to create massive mountain ranges.

Near the end of his career, he coordinated the activities of Scripps' research fleet, scheduling voyages and allocating resources. He also helped create and served on the University-National Oceanographic Laboratory System, which coordinates operations of research ships throughout the world.

In the 1950s, he joined Project Mohole, which was designed to retrieve a sample of material from the Earth's mantle by drilling through the Mohorovicic discontinuity, which resides as much as three miles under the ocean floor and up to 25 miles below the surface of continents. Shor and Scripps geophysicist Russell W. Raitt identified the best location to drill the hole, off the coast of Hawai'i, but the project was canceled by Congress because of cost overruns and poor management.