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In the Pacific Northwest
– Excerpted from a November,1999 article in Oregon Geology by Elizabeth L. Orr and William N. Orr, Department of Geological Sciences, University of Oregon, Eugene
Oregon is known for its wonderful diversity of natural landscapes including deserts, deep river canyons, high snow-covered mountains, flat well-watered fertile valleys, and a coastline with quiet coves and dramatic headlands. Unavoidably, however, the breathtaking scenery goes hand in hand with geologic processes that can be responsible for recurring and destructive hazards.
In the Pacific Northwest, natural geologic catastrophes may be placed into five categories: floods, landslides, earthquakes, volcanic eruptions, and tsunamis. All five of these catastrophes have occurred in Oregon within the past century. Quite often the effect of two or more events occurring simultaneously greatly accentuates the destructiveness of the episode. Floods are nearly always accompanied by landslides, mudflows are often a significant part of volcanic activity, and a major quake following a flood results in a multitude of large and small landslides. Earthquakes in coastal areas frequently precede tsunamis.
The long view of geology recognizes that most geologic processes shaping the topography are remarkably slow and that all of these features can be explained by ongoing natural events. Oregon‘s landscape is being continuously shaped by crustal plate movement, heavy winter rainfall, and ocean storms.
Are hazardous geologic occurrences increasing in frequency? There is a tendency to suggest that this is the case. In a headlong rush for news items, the media will often pump up any event to catastrophic levels— even when no deaths and only minimal property damage have occurred. Additionally, the wonder of modern communication is such that news stories are pulled in from remote corners of the globe, while 50 years ago they would have been missed or rated only a line in a newspaper.
On the other hand, it is true that the increase in population and the dispersal of populations into some areas previously considered marginal or unsafe dictate that more of these natural disasters will be witnessed than before.
Humans themselves often aggravate disastrous situations by placing themselves in harm’s way, and activities such as redirecting rivers, over-steepening slopes, or clear-cutting may create problems. Moreover, development of dwellings and highways is so widespread and growing that natural disasters are much more likely to impact mankind and cause loss of life and property than at any time in the past.
Reduce the risk from natural hazards - a resource guide
Oregon Emergency Management
The Natural Hazards Program from the Department of Land Conservation
Learn more about the geologic forces that cause natural hazards from the series "Savage Earth" from PBS Online
Learn about Senate Bill 13 - Earthquake preparedness drills
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