Mar

10

Quiz, from anonymous

March 10, 2017 |

 I sent this to my politically opposite progeny:

Who can guess why the creekbeds on the upper right don't continue toward the lower left, and some appear displaced?

One answered "Obama" and the other "Moonbeam".

I wrote back:

OK X came closest and Y gets 2nd place.

The diagonal line going from lower right to upper left is the San Andreas fault, a hundred miles from here in San Luis Obispo county. As you can see, the dry creekbeds end abruptly at the fault - and some even jog up and left after meeting the fault. This is because the left (West) side is the Pacific plate, and the right (East) side is the North American plate, and the Pacific plate is moving northward past the NA plate. Over thousands of years, the creek beds to the West of the fault shift North. Water run-off runs down the creek beds until intersecting the fault, and there either follows the fault or goes underground - because the bedrock is pulverized along the fault. You can see how some of the older beds (more eroded) used to line up but are now displaced.

There is evidence that much of the movement occurs during large earthquakes. Recently there was a study indicating there are very large earthquakes along the San Andreas about every 100 years (very large = 10-100X Northridge energy). The last big one along the southern portion of the fault was the Ft Tejon earthquake of 1857…160 years ago. ie, we're overdue (with the caveat that it could be decades or even another 100 years, though the longest interval they found was 200y):

Why are your politically correct answers correct? Because politicians are attracted to self-aggrandizing emblematic issues, while neglecting critical infrastructure needs. There should be many structural upgrades to roads, buildings, power, etc to better prepare for the big one. And of course the recent California drought will continue - despite record rainfall in parts of the state - because 92% of the runoff is lost as there aren't enough good reservoirs. It is more important to protect the delta smelt than farmers (so we can buy produce from Mexico where they only protect drug kingpins), build a bullet train from Fresno to Modesto, save the planet from global warming (even though man's contribution is uncertain), and squander taxpayer dollars to fight the feds for the right to hoard illegal immigrants.


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