Catastrophic Hazards

Bill in DC sent me this link this morning, When Nature's Wrath Is History's Reminder, and I was going to do a post on it. Jazz did a nice job over at Running Scared so all I'm going to do is add a little from the perspective of a west coaster with training as a geologist.

From Geologic Hazards on the Oregon Coast

Catastrophic hazards:
Catastrophic hazards are associated with earthquakes and related tsunami's. The eastward-moving Juan de Fuca tectonic plate dives under the westward-moving North American plate just off the Oregon coast at the Cascadia Subduction Zone. Powerful earthquakes up to magnitude 7 can take place in either the North American or the Juan de Fuca plates. The Cascadia Subduction Zone, however, is capable of generating even larger earthquakes — up to magnitude 9.

These larger earthquakes would occur under the ocean and can cause destructive tsunami's that can strike the coast between 10 and 30 minutes after the earthquake. The geologic record shows that these large Cascadia Subduction Zone earthquakes and accompanying tsunami's occur every 500 years, plus or minus 200 years, with the last one having occurred about 300 years ago.

Catastrophic hazards on the coast associated with earthquakes include severe ground shaking lasting up to 5 minutes; liquefaction of saturated, unconsolidated soils such as sand or silt; numerous landslides; land subsidence and flooding; and tsunami's.

tsunami's associated with Cascadia subduction zone earthquakes have repeatedly buried tidal marshes in sand along the Oregon coast many times over the last few thousand years.

What that means is earthquakes and resulting tsunami's just as great as the one in the Indian Ocean occur along the coast of the Pacific Northwest every 300 to 700 years and yes the last one was 300 years ago. An earthquake of that magnitude would destroy most of the inland population areas in Oregon and Washington. The earthquake would occur relatively close to the coast so the tsunami would arrive in a matter of minutes.

The history of civilization is short but the history of the earth in long. Catastrophic events are normal and common. And non catastrophic cycles may prove to be catastrophic for civilization such as normal fluctuations in the global climate. Some 50,000 years ago changing climate conditions in Africa forced humans to start migrating north and east.
All we can do is prepare for the ones we can. There is little we can do to prepare for massive earthquakes or events like a mega tsunami from La Palma but we can prepare for the inevitable global climate change and slowly rising sea levels that will result. The time is now.