Moffett Field in Santa Clara County, California — The American West (Pacific Coastal)
Granodiorite Boulder From Antarctica
Photographed by Adam Margolis, June 9, 2026
1. Granodiorite Boulder From Antarctica Marker
Inscription.
Granodiorite Boulder From Antarctica. . This boulder was collected in the Ross Sea during the 1984 research cruise of the USGS ship S.P. Lee It was dredged at a depth of 2000 meters (6,500 feet) from the flank of Iselin Bank, the northern extension of a wide basement ridge 100 kilometers (60 miles) wide. It is reportedly one of the largest samples yet collected from the Antarctic continent. The composition of granodiorite is similar to plutonic rock located in the Transantarctic Mountains situated onshore 700 kilometers (450 miles) to the west. It is, however, believed to have been carved from granitic rocks on Iselin Bank itself. If so, it represents a fragment of the slab of continental crust left behind during the break apart of Antarctica, Australia and New Zealand about 80 million years ago.
This boulder was collected in the Ross Sea during the 1984 research cruise of the USGS ship S.P. Lee It was dredged at a depth of 2000 meters (6,500 feet) from the flank of Iselin Bank, the northern extension of a wide basement ridge 100 kilometers (60 miles) wide. It is reportedly one of the largest samples yet collected from the Antarctic continent. The composition of granodiorite is similar to plutonic rock located in the Transantarctic Mountains situated onshore 700 kilometers (450 miles) to the west. It is, however, believed to have been carved from granitic rocks on Iselin Bank itself. If so, it represents a fragment of the slab of continental crust left behind during the break apart of Antarctica, Australia and New Zealand about 80 million years ago.
Location. 37° 24.713′ N, 122° 3.342′ W. Marker is in Moffett Field, California, in Santa Clara County. It is at the intersection of S. Akron Road and Severyns Avenue on S. Akron Road. Touch for map. Marker is at or near this postal address: 450 Severyns Avenue, Mountain View CA 94043, United States of America. Touch for directions.
Regionally, this marker is in California’s San Francisco Bay Area and on the Coast Ranges. It is also on the American Pacific Coast. Globally, it is in North America, on the Ring of Fire, in the Pacific Rim, in the Western Hemisphere, in the Western World, and in the Anglosphere. Historically, it finds itself in what was once New Spain and also Mexicos Alta California.
Other nearby markers. At least 8 other markers are within 2 miles of this marker, measured
Credits. This page was last revised on June 18, 2026. It was originally submitted on June 10, 2026, by Adam Margolis of Mission Viejo, California. This page has been viewed 7 times since then. Photos:1, 2. submitted on June 10, 2026, by Adam Margolis of Mission Viejo, California. • Andrew Ruppenstein was the editor who published this page.
