Carquinez Strait

11 Carquinez Scenic Dr, Martinez, CA 94553, United States

 

The Carquinez Strait is a small tidal strait in northern California. It is part of the tidal estuary of the rivers Sacramento and San Joaquin as it flows into the Bay of San Francisco. The stretch is 13 km long and connects the Suisun Bay, which collects the waters of the combined rivers, with the San Pablo Bay, the northern stretch of the San Francisco Bay.

 

The straits formed in prehistoric times, at the end of one of the past ice ages, when the inland lake filled the present-day Sacramento and San Joaquin valleys. The melting of ice from the Sierra Nevada mountain range increased the level of the lake as the seismic activity created a new outlet to the Pacific Ocean, draining the lake into the ocean and revealing the two valleys. The valleys have developed into highly productive agricultural areas and have driven California 's economy into the powerhouse that it is today.

 

Andrei Sarna-Wojcicki, an emeritus geologist from the U. S. Geological Survey (USGS) estimated that the Carquinez Strait was possibly formed between 640,000 and 700,000 years ago, when most of modern California emerged from an ice age. The present Sacramento Valley and San Joaquin Valley were filled by a massive (now extinct) lake called Corcoran Lake. Initially, this lake had washed into the ocean from a valley near today's Monterey. However, ongoing seismic activity has lifted the coastal mountains enough to plug this outlet. Around the same time, the ice melting away from the Sierras increased the water level in Lake Corcoran until the lake started to sculpt a new outlet into the ocean. At some point, the coastal barrier collapsed between the cities of Crockett and Benicia today, releasing water from the lake in a cataclysmic flood.

 

It forms part of the boundary between Solano (north) and Contra Costa (south) counties and is approximately 15 miles (25 km) north of Oakland. The cities of Benicia and Vallejo lie on the north side of the Strait, while Martinez, Port Costa and Crockett are on the south shore. The Napa River enters the Strait, through the short Mare Island Strait, near its entrance to the Bay of San Pablo. Its watershed occupies 62,500 square miles (162,000 km2), nearly 40 % of the total land area of California.

 

It is crossed by two highway bridges: the Carquinez Bridge on Interstate 80 and the Benicia-Martinez Bridge on Interstate 680. Every highway bridge consists of two parts. Interstate 780 links the two highways on the north side of the Strait. State Route 4 links these highways to the south of the Strait and to the inland.

 

The Capitol Corridor, California Zephyr, and Coast Starlight trains use the rail bridge just east of the Benicia – Martinez Bridge. The rail ferry, with the Contra Costa and Solano ferries, provided service across the stretch near the site of the new rail bridge until the railway bridge was completed in 1930.  The high pylons bearing power lines also cross the straits. The Carquinez Strait Powerline Crossing was the world's first powerline to cross a large river.

 

The channel is navigable and is used by both commercial and military shipping. Deep water ship traffic bound for both the Port of Sacramento and the Port of Stockton passes via the Stockton Deepwater Shipping Channel and the Sacramento Deep Water Ship Channel. The Carquinez Straits are part of the Baldwin Deepwater Shipping Channel.

 

The narrow gap in the coastline that forms the strait has contributed to the creation of the delta of the San Joaquin – Sacramento River, the inverted delta of the river, a rare geological feature upstream. The stretch is too narrow to allow the passage of large quantities of floodwaters produced over the years with heavy rainfall and snowmelt events. Since the Delta region is the first to be filled and the last to be drained in a flood event, the silt and soil have more time to drop out of suspension, creating an inverted river delta feature.