Corcoran Lake filled the Central Valley 760,000 years ago, including this location, and drained to the ocean at what is now Monterey Bay. Two hundred thousand years later, tectonic forces plugged that outlet and tilted the lakebed to the north. The surging lake then overtopped the East Bay hills and carved a new drain, the Carquinez Strait. Today the strait funnels runoff from the entire Delta watershed to the sea and serves as the only path for ocean tides moving through the Bay into the Delta. Fish, seals, sea lions, and occasional whales pass between salty seas and fresh rivers and sloughs, while ships from the Pacific navigate the strait to inland ports such as Pittsburg, Stockton, and Sacramento. From an ancient flood-worn hillside to a nautical thoroughfare of today, the Carquinez Strait is one of the many spokes of water linking California through the hub of the Delta.