Will a really big earthquake sink Western California?

Given California's history of earthquakes and major fault lines, it's not surprising that people speculate about parts of California breaking off into the ocean. Fortunately, seismic forces don't work that way, as Marshall Brain explains in this episode.

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Episode Transcript

Speaker 1 (00:00):
Welcome to Brainstuff from house stuff Works dot com where
smart happens. Hi. I'm Marshall Brain with today's question, and
i also have a funny little story that I'm going
to stick at the end of this podcast and ask
you a question about it. So here's the question. Is

(00:22):
it true that scientists are predicting a really big earthquake
that will sink western California. This often comes up when
people talk about earthquake activity along the Pacific coast of
the United States. Seismologists have predicted that a massive scale
eight point oh or higher on the Richter scale earthquake

(00:42):
will shake that region sometime within the next thirty years
or so. This is the so called Big One that
makes many California residents understandably nervous and inspires a variety
of apocalyptic disaster speculations. But while the Big One would
definitely reek mass destruction, it would not sink part of

(01:03):
California into the ocean, nor would it break the state
off from the rest of the country or anything like that.
The idea comes from a misunderstanding of the seismic forces
that cause earthquakes in the region. To begin with, powerful
earthquakes occur frequently along the West coast of the United
States because the region is near a boundary between two

(01:24):
tectonic plates. If you've read How Earthquakes Work on How
Stuff Works, then you know that the Earth's surface is
made up of large, rigid plates that slowly drift over
the mantle layer below them. At the boundaries between these plates,
a number of things can happen. The Pacific Plate and
the North American plates simply grind against each other, one

(01:47):
creep slowly northwest and one creeps southeast. This boundary forms
a fault line that extends under the ocean and on
land along the West coast of the United States. The
San Andreas Fault in California is the piece that's on land.
Smaller faults form in the crush material near the boundary
line due to the forces of the plates pushing on

(02:09):
each other. Friction builds up along the fault because the
two sides are pushed very tightly together. If the force
of friction exceeds the forces moving the earth, then the
two sides will become locked, so they stop creeping. When
this happens, tension builds up along the fault line until

(02:29):
the force of movement is great enough to overcome that
force of friction and to break the lock. Then the
pieces of Earth suddenly snap into place, releasing a huge
amount of energy that causes big earthquakes in the Earth's crust.
Many scientists estimate that there is enough tension built up
along some locked California faults that when they do finally slip,

(02:52):
the earthquake will be extremely powerful. The Hayward fault particularly
concerns these scientists because it runs are heavily populated areas
in and around Los Angeles. The notion that part of
California will break off, though, was likely inspired by the
San Andreas fault. After all, since the fault goes right

(03:13):
through California, one part of the state is on the
Pacific Plate and one is on the North American Plate.
If those plates are moving in different directions, it makes
sense that the two pieces of California will move in
different directions too, and this is indeed the case. But
even in a massive shift along the fault, the plates

(03:34):
travel an incredibly short distance. It's a matter of ten
or twenty feet at most, and even the most extreme shifts,
the tension can't build up to the point that one
entire massive land will shift many miles in relation to
another one, so you will not see any sizeable piece
of land breaking away from any other. Instead, the pieces

(03:56):
of land will move away from each other slowly, very
very slowly, taking millions of years to make large scale changes.
One end of California may slowly drift so that it
eventually is underwater after millions of years, but this can
hardly be construed as sinking into the ocean. Pieces of
land don't just fall into the ocean, because that's not

(04:20):
how tectonic plates work. So let me shift gears here
and tell you a funny story. As many of you know,
I have been on a diet for about fourteen weeks
now and I've lost thirty seven pounds. So I got
this comment on one of my dieting blog posts from
a reader named Christine, and here's what she says. You're

(04:42):
doing a phenomenal job. I hope that you will continue
with updating us each week because reading your posts keep
my momentum going. Also, I listened to your podcasts and
I wanted to mention that you sound thinner. Sound is
in all caps. You don't sound throaty, almost as if
you've lost weight around your neck, so that is odd.

(05:05):
If you've ever read my blog posts about this diet
I've been on, it's called the Ducan Diet, and it's
worked pretty well to lose thirty seven pounds in roughly
three months. But I never would have expected or predicted
or calculated that it would have any effect on my voice.
So here's a question I'd like to ask. Do you
think my voice sounds different than say, three months ago.

(05:29):
If you listen to the podcast regularly, you know you've
probably heard my voice over a couple of months period.
Does it sound any different to you? And if it does,
would you mind leaving a comment? There's Facebook dot com
slash brain stuff. You could go there and just drop
a comment on the page. I just be curious to
know if this is something that is audible to people,

(05:50):
or if not, or if you don't use Facebook, then
email me at m brain at how stuff works dot com.
So it's Facebook dot com, slash brain stuff or m
brain at how stuff works dot com. I just be
curious if you can hear any difference. Thanks for more
on this and thousands of other topics, visit how stuff

(06:11):
works dot com and don't forget to check out the
brain Stuff blog on the how stuff Works dot Com
home page. You can also follow brain Stuff on Facebook
or Twitter at brain Stuff H. S W.