Ancient Quakes and Paleo-Tsunamis

Oceanic crust is formed at a mid-ocean ridge, ...

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Earthquakes have been happening for a long time. Our planet suffered from them almost from the time solid ground and rock first formed in small patches on the surface of our smoldering world. These rafts of rock floated on a molten lava sea and occasionally ran into each other and finally at some point covered the whole surface. But the molten rock below still circulates, by convection and rotation and it’s this movement of molten and some now plastic rock below the solid tectonic plates that cause the plate motion and earthquakes we now enjoy.

It takes a lot of force to push huge plates around and make then crash and slide against each other. The plates get stuck against each other and once in a while, and by that I mean almost constantly, there is some plate boundary thay lets go a bit and causes what we see as a quake.

Ancient quakes leave traces. They can leave small traces like fractures in rocks and a bend in a fence. They can leave huge traces like whole areas of land moved up or down and tracts of land covered in the aftermath of a tsunami. By looking for these traces we can see what has happened in the past and so learn of our future. Places like the lowlands in the Cascadia Fault zone, the zone from central BC to northern California that have layers of sand, silt and mud hold these traces for us to read and learn.

We have to learn from these signs because the record the past before we had the ability to write. As well there are traces of the truth in our oral traditions, the stories and myths our forefathers repeated generation after generation. We know we have had earthquakes in the past and devastating tsunamis. But we build our cities in the tsunami zones. We build our buildings with no protection from the monster waves, and we ignore the signs and are dooming ourselves to a fate we can see.

Earthquakes are not periodic although some look like they are. They are however not happening without warning. there are signs if you go back far enough and can read them. A quake happens after two major things happen, a fault gets stuck and enough pressure is applied to unstuck it. On the Cascadia Zone for instance the whole zone from north to south is stuck. Its caught on something, pressure is building. In the past this pressure has caused uplift in the North American Plate and what are salt marshes now were lifted high enough that trees that require fresh water were able to grow. That list is happening indicating the pressure is mounting. It takes a lot of pressure to push this land up so there is a tremendous pressure load but is it enough yet?

Predicting what is enough is where our paleo-tsunami evidence comes in. The load is high enough to have an earthquake now. But the land lift is not as high as any of the previous mega tsunamis was, so there could still be a quake now but it won’t make the mega tsunami with the current pressure load. But it will be soon so what I think people should do. Move. Inland and to higher ground. Abandon the old cities except for the people who must work there for things like ports. You just can’t move a port above sea level. If you fish insure your boat and move you family to higher ground.

With the tsunami risk and climate change, development at sea level is no longer tenable. We are already seeing both have impacts on places around the world. We know both are coming, especially in certain areas, Japan, New York, Cascadia. Not taking action is inexcusable. You could try to build a tsunami dike around a city, like Vancouver, but how high is high enough? The maximum run-up of the Japan Tsunami was 47 meters. How high and thick a wall would you need? And how would you close the  hole at the port and waterfront and still make it usable?

The Cascadia Mega Quake is coming. It may be 100 years, it may be tomorrow but it is coming and there is nothing we can do to stop it. So prepare or deal with the aftermath.

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About echlinm

Computer Programmer/Systems Analyst/Hacker S31
This entry was posted in Earth Science, Earthquake and tagged , , , . Bookmark the permalink.

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