This cache is located within the confines of the Anacortes Community Forest Lands and is placed with permission. The ACFL covers nearly 2,800 acres within the City of Anacortes, with 50 miles of multiple use trails. If you want to further explore the area after “finding” this earthcache, you may want to pick up a map. (More info Click here.) While Most of the hikes are not difficult, it could get confusing without a map if you are not familiar with the trail system.
The posted coords will take you to parking. I’ve also included waypoint coords for the first question to answer and two viewpoints. For the other answers you are encouraged to explore the small summit with its lavish views of the San Juans, the Olympics, Cascades and mountains of Vancouver Island.
At 1,273 feet, Mount Erie is the highest point on Fidalgo Island. The mountain has a unique and somewhat puzzling composition. Many geological forces have occurred during the formation of Mt. Erie. Forces of heat, pressure, uplift and erosion have all combined with time to create this spectacular setting.
Origin of The Rock:
Technically speaking, Mt. Erie is a diorite pluton. The term pluton originated from Pluto, the classical god of the underworld. A pluton in geology is a body of intrusive igneous rock that crystallized from magma slowly cooling below the surface of the Earth. (Note that if the molten magma reaches the surface, a volcano is the result instead.) A mass of plutons over an area of 40 square miles is called a batholith. One fine example of a batholith in Washington State is the Golden Horn Batholith near Washington Pass. (See earthcache, Early Winters Glacier GC1DGZY here .)
The area then experienced uplift and erosion and was subjected to intense folding and faulting. At this point most of the deposited older sediments had been eroded away exposing the plutons of diorite. (Diorite is an extremely hard rock and not easily eroded.) Mt. Erie probably also experienced intrusion by dikes associated with the formation of oceanic seafloor. This indicates that the area may have experienced periods of submersion, as the Juan de Fuca plate subducted underneath the North American plate.(This whole process of constant uplift and erosion followed by accretion is thought to have created the unique ophiolites associated with the San Juan Islands and primarily the Fidalgo Complex located near the mountain.)
Glacial Erosion:
During the next period the area experienced many glacial periods and retreats. These periods of glacial erosion were separated by cycles and continue to present day. Such evidence for the glacial erosion of Mt. Erie itself can be observed at the summit by large striations on the rockface. It also has a spectacular ‘plucked’ face on one side, (a favorite for rock climbers), often referred to as a Stoss and Lee feature. Plucking is a process of erosion in which the glacier pulls off loose pieces of bed rock. Usually mountains subjected to plucking are asymmetrical. It will have a gentler slope on its up-glacier side and a steep to vertical face on the down-glacier side. The glacier abrades the smooth slope that it flows along and indicates the direction of its movement.
To qualify as a "find", email, (do not post online), the answers to the following questions. Please e-mail us at the same time you log your find. Failure to do that in a timely manner will result in a log deletion.
1) At WP1 what dates do you find here? (Hint: it is not the benchmark.) Please do not post any pictures of it!
2) The stoss and lee feature indicates which heading the glacier was traveling at when it passed over Mt. Erie. Based on your observations, please make an educated guess which direction it traveled after leaving here.
3) Since the glacial erosion has caused the mountain to become disproportional, compare and contrast its sides.
Post a picture of you or your GPSr with some of the views found on this mountain.
I hope you have learned a thing or two about the origin of this mountain and thanks for visiting the Anacortes Community Forest Lands.
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Warning: Earthcaches come with a unique set of rules and activities that must be met
before successfully logging. Failure to comply will result in a log deletion.
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