PubTalk 11/2005 — Shifting Shoals and Shattered Rocks

HOW MAN HAS CHANGED THE FLOOR OF SAN FRANCISCO BAY

by John Chin and Florence Wong, Geologists

• San Francisco Bay is one of the world's finest natural harbors and a major center of maritime trade
• All ships visiting bay ports are funneled through the central bay
• Bedrock knobs that rise from the central bay floor have been repeatedly blasted to accommodate vessels of increasingly deeper draft
• Sediment dredged from harbors and shipping channels has been disposed of on the bay floor
• Since the early 1900s, the bay floor has been mined for sand and gravel
• New tools are allowing scientists to create detailed views of the bay floor, revealing changes that man has made since the Gold Rush