Oregon Islands at Coquille Point EarthCache
Oregon Islands at Coquille Point
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Along the Oregon coast, colossal rocks can be seen jutting out of the Pacific Ocean. Each of these rocks is protected as part of Oregon Islands National Wildlife Refuge. The wildlife using offshore rocks, reefs and islands are extremely susceptible to human disturbance, thus they are closed to public entry year-round to protect the wildlife. You will be making your observations for this Earthcache from the paved walkways at the Coquille Point Unit of the refuge.
For more information about visiting this area check out the Oregon Islands National Wildlife Refuge website.Thank you to the National Wildlife Refuge for allowing this Earthcache.
Oregon Islands
The geological history of the Oregon Coast includes volcanoes, tectonic shifts, and erosion.
The Oregon Coast Range is a belt of uplifted land lying along the Pacific Coast of Oregon. The uplift is a result of plate convergence. About 400 km west of the Coast Range lies the spreading center, which separates the Pacific plate (which extends to just east of Japan) and the Juan de Fuca plate, which descends under the North American Plate along the Cascadia subduction zone. Collisions of these plates as well as volcanic activity produced the Oregon Islands.
The island formations were created when volcanic hot basalt flow rapidly cooled upon meeting the salt water of the ocean. The lava flow is characterized as basalt, and when basalt erupts underwater or flows into the sea, contact with the water quenches the surface and the lava forms a distinctive pillow shape, through which the hot lava breaks to form another pillow.
The pillow basalt formations moved along Earth’s crust and in a tectonic collision were pushed deep underneath the North American plate. Under great pressure they were uplifted and exposed. As soon as rocks get pushed up the ocean starts eroding them down. The south coast of Oregon is characterized by faster tectonic uplift than up north, resulting in headlands rising faster than wind, rain, and waves can knock them down. Many of the islands at Bandon are composed of blueschist, an uncommon rock formed when volcanic rock is exposed to conditions of high pressure and low temperature.
The hard, durable rocks off of Coquille Point are some of the oldest on the Oregon Coast. Sea stacks, knobs, rocks, and islands are large and numerous here because they are shaped and eroded very slowly. All this shifting, colliding, bumping, grinding, and erupting produced a coast comprised of many rock types. All have been exposed to millennia of wind, rain, and pounding waves. Harder rocks remain longer while softer materials erode more quickly creating the varied coastline you see today.
To claim credit for the Earthcache use your GPS and observation skills to study this area and the Oregon Islands. Send me the answers to these questions through my Geocaching profile. All reasonable attempts will be accepted.
1. What is the elevation at ground zero?
2. Based on the elevation estimate the height of some of the tallest islands near ground zero.
3. Observe and tell about the feature of the large island to the west of ground zero, labeled as Elephant Rock on maps and nearby signs, that is not found in the other nearby islands. Hint: it involves erosion.
Sources:
Oregon Islands National Refuge
A Brief Summary of Oregon Coast Range Geology, Geomorphology, Tectonics, and Climate
Visionlearning
Orr, Elizabeth and William Orr, and Ewart Baldwin. Geology of Oregon. Kendall/Hunt Publishing, 1992, 4th edition
Additional Hints
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Treasures
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