The earth beneath our feet

(This was a quick Facebook post and is a bit of a mess but I’ll leave it as is….)

In wonderfully telegraphic prose, a comrade posted “earthquake in japan now. pacific rim is heating up. cali needs to be ready?”

A ha. Rocks. Earthquakes. The very earth beneath our feet. After myself, my other favorite subject. I actually decided against a career in geology for a career in punk rock, epilepsy and writing about me.  Say a’a, the doctor said, and out flowed this:

About 90% (I began) of the world’s earthquakes happen in the Pacific Rim’s Ring of Fire, so it’s shaking all the time. There’s no connection between California and Japanese quakes, though. Our quakes happen because the eastern spreading portion of the Pacific plate (and a smaller connected plate) are being pulled under the North American plate, while Japanese quakes happen because Japan sits where the western spreading portion of the Pacific plate is being pulled under the plate that eastern Siberia is on. The fault zones are unconnected.

In California the plates are sort of moving past one another, the Pacific plate sliding beneath the North American plate at an angle, while in Japan the plates together slam head on. Subduction is not a pretty process. Geology, mostly, is violence in slow motion, a few inches a year. Those undulating layers you see in California road cuts are layers once horizontal subjected to immense pressures. The bend slowly. Sometimes, though, you see layers shattered, as if they exploded. That’s because often they did. You might be looking at the frozen remains of earthquakes. Rock busts into fragments and the surface above shakes. Sometimes a little. Sometimes a lot. The San Andreas Fault is where two tectonic plates slide past each other at about an inch and a half per year. Sometimes they catch and remain stuck till enough pressure builds up that they uncatch and destroy San Francisco. But there is vastly more energy to be released when plates collide directly than when they slide past each other, hence the frequency and power of Japanese quakes. Japan actually is the result of two (or is it three, I can’t remember) plates being dragged under (or subducted) beneath two other much larger plates. In Japan you have these two or three separate collisions (not just the one I alluded to in an earlier paragraph, keeping things simple), and each collision is vast and inexorable, and all that friction and compression and crunching and pushing causes nearly incessant earthquakes of sometimes unbelievable power and destructiveness. Indeed, Japan itself is a result of these collisions, with sea bed forced upward and vast amounts of the liquid rock mantle being released from cracks in the crust through volcanos. Geologically it’s a helluva mess, volatile and unstable and virtually quivering and literally quaking with pent up seismic energy.  Just be thankful, Californians, that we have nothing even remotely similar to this. (They do in Alaska, which is how Anchorage was leveled in 1964, the Pacific Plate suddenly lurching violently and shoving itself beneath the North American Plate, leaving one side of the street thirty feet higher than the other.) The San Andreas may pop off every couple generations. Japan has giant quakes every couple years. They handle them with aplomb. Their buildings don’t fall down. Port au Prince Tokyo is not. It’s not even Fillmore.

As for the devastating Nepali quakes these past several days, those are the result of India slowly crashing into Asia for the past 50 million years. It’s weird to think that in that span of time there have probably been a million huge quakes in what is now the Himalayas, just like these last two. A million quakes raising the earth six inches each time is what created the Himalayas. The top of Mount Everest was at the bottom of a shallow sea a half billion years ago. The rocks way up there are full of fossil crinoids. Imagine how many earthquakes it took to raise them 30,000 feet into the air.

Next time you pass through a roadcut, take a look at the rocks exposed. The violence in those bent and twisted layers is incredible. So much power moving a couple millimeters a year. The earth moves in millions of years. We are nothing, our entire lifespan a geologic nanosecond, like we aren’t even here.

Still, I love rocks.

A roadcut on the I-40 outside Kingman AZ, with a layers of sediments as horizontal as when they were deposited being split in two by a young fault. Come back in a few million years see what it looks like.

A roadcut on the I-40 outside Kingman AZ, with layers of sediments as horizontal as when they were deposited, now being split in two by a young fault. Come back in a few million years to see what it looks like.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s