Developments in Brief : Like Many Residents, California May Have Come From Somewhere Else

Parts of what is now California may have risen up from the sea and then been carried to North America from as far away as the area around the Equator, according to two Stanford scientists.

Geophysicists John Tarduno and Michael McWilliams say that a patch of red limestone near the Northern California community of Laytonville came from south of the Equator and was carried at a rapid clip on a fast-moving plate of the Earth’s crust. They estimate that this all took place 50 million to 70 million years ago. The estimate fits with the rate of travel geologists proposed for the Kula plate, now totally subducted under North America.

They said the plate that may have carried the Laytonville limestone has long since been digested deep inside the Earth, but there is a plate currently scraping against Japan and other Asian lands that rim the Pacific Ocean. Previously, Tarduno and McWilliams helped show that Black Mountain, the tallest hill on the ridge that runs west of the Stanford campus, once was a tropical island.