Tsunami! EarthCache
GeoCrater: I am regretfully archiving this cache since there's been no response from nor action by the cache owner within the time frame requested in the last reviewer note.
GeoCrater
Geocaching.com Community Volunteer Reviewer
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Devastating waves called tsunamis can strike the Oregon coast at any time. These giant waves are caused by great undersea earthquakes. Such earthquakes can occur along the Cascadia Subduction Zone, one of the largest active faults in North America. This fault zone lies 32 to 70 miles offshore and roughly parallels the coast.
The Cascadia Subduction Zone is formed from the Juan de Fuca Plate being pushed under the overriding North American plate along the coastline. This movement is caused by magma working its way up from the interior of the earth to the oceanic crust between the Pacific Plate and the Juan de Fuca Plate, building onto each and pushing them apart. This addition to each pushes the Pacific Plate west and the Juan de Fuca Plate east. This area between the plates where the magma surfaces is called the Juan de Fuca ridge. As the Juan de Fuca Plate subducts under the North American Plate it generates seismic and volcanic activity.
The Juan de Fuca Plate is named after the 16th century explorer of the same name. It is the smallest of the earth’s tectonic plates and is actually the remnant of the once vast Farallon Plate, which has largely subducted under the North American Plate. The Juan de Fuca Plate has itself fractured into three pieces. The entire group maintains the name in some references while, in others, only the central piece does. Where identified separately, the piece to the south is known as the Gorda Plate and the piece to the north is known as the Explorer Plate.
This subduction system has formed the Cascade Range, the Cascade Volcanic Arc, and the Pacific Ranges, along the west coast of North America from southern British Columbia to northern California. These, in turn are part of the Pacific Ring of Fire, a much larger volcanic feature extending around much of the rim of the Pacific Ocean
Tsunamis are dangerous and destructive. They have struck the Oregon coast repeatedly in the past and will do so again in the future. Tsunamis can follow within minutes of an earthquake. They move rapidly but quickly run out of water as they sweep inland and uphill. Flooding can occur several miles inland along rivers and streams. Most tsunamis are not solitary waves; many large waves may strike the shore over the course of several hours.
To log this cache you must:
1) Using the map on the sign labeled “Oregon Geology,” how far are you from the Juan de Fuca Ridge?
2) Using the same map, how far are you from the Cacadia Subduction Zone?
3) And, to prevent armchair caching, what are the four symbols at the bottom border of the sign (description and name)?
PLEASE, DO NOT LOG A FIND UNLESS YOU HAVE SENT YOUR ANSWERS.
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