When will California fall into the sea?

Dear Cecil:

Cecil, can you predict when California will fall into the sea?

Cecil replies:

Yes, but I don’t want to be held responsible for causing a panic, so I’ll just tell you what the geologists say.

It all depends on what you mean by “fall into the sea.” If you mean “when will California break off the continent and sink the ocean floor,” the answer is “never.” The sea, you see, is only about two miles deep. California is about twenty miles thick.

Perhaps you mean “when will there be a major earthquake?” (An earthquake centered at the San Andreas Fault could involve a lot of vertical slip, which could conceivably put some California coastline underwater.) In that case the answer is “any day now, maybe.”

Some geologists believe that the strain built up around the San Andreas Fault is already reaching the level that caused the great San Francisco earthquake of 1906. Others say the big day could be 100 years away. This is the sort of razor-edge precision you come to expect from rock jockeys.

If you simply mean “when will California slide away to oblivion?” the answer is about 50 million years. The Pacific “plate,” which carries the western sliver of California, is sliding past North America at the dizzy rate of about two inches per year. Someday, Los Angeles will slide under the earth’s crust near the Aleutian Islands, but this is no time to worry about it–I’ll let you know when it’s time to start packing.

Send questions to Cecil via cecil@straightdope.com.

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