Ocean Forces View (Mendo Coast) Earthcache EarthCache
Ocean Forces View (Mendo Coast) Earthcache
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
As an earthcache, there is no “box” or “container” to discover. Rather, with this cache, you discover something about the geology of the area. For more info, consult www.earthcache.org
This cache can be done simply by stepping out of your car to get a good (EXCELLENT) view, then observing what you see! You were going to stop here anyway…right?
Logging Requirements:
Send the answers to #1-#4 to me through my geocaching profile. DO NOT post the answers to any logging requirements on this site.
1. List the name “GC24PJF Ocean Forces View Earthcache” in the first line of your email. Also, list the number of people in your group.
2. In the eroded cliffs north of you, what LAYERS IF ANY do you see? (What rock colors and how many distinct color bands?)
3. OBSERVE the “pillar” of rock just off the coast to your west (about 200 yards away). Is it a chimney (taller and skinny) or a sea stack (wider and flatter on top)? Is it composed of greywacke or basalt (see description)?
4. What is the elevation at your location?
5. (Per current gc.com guidelines, photos are no longer allowed to be required. HOWEVER they are encouraged, since they can help clarify that you have visited the location if your other logging requirement answers are vague). Post a picture of yourself and/or your GPS with your log that shows The town to your north in the background. DO NOT show any of the pertinent information panels in your picture or your log may be deleted. Please, NO VACATION PHOTOS from years past!
I will only respond if you have incomplete logging requirements. Go ahead and log your cache
This earthcache is at a pullout just south of the town of Mendocino. I pulled out to this spot to grab a traditional cache and couldn’t help but see the earthcache view!
Geology:
The Sea Stack: The sea stack is composed of greywacke. Faulting and natural cracks in thegraywacke allow wave action to eat away at the weaker joints in the rock until sea caves develop and then the rock and terrace deposits above eventually fall into the ocean as the caves widen. Fractures sometimes allow rock falls without first forming caves. This process continues in the weaker rock joints and layers surrounding the stack until it is left on its own.
The sea stacks you see along this coast, unlike those further north in Oregon, are composed almost entirely of Graywacke….thus notice their fractured nature.
The cliffs you see before you are formed by two actions – primarily wave erosion, and secondarily the natural fracturing of the greywacke. At this point the San Andreas fault is 5-6 miles off the coast so does not provide any direct actions to the sea stacks.
Graywacke in this area was formed by subduction action as the North American Plate collided with the Farallon Plate, and pulverized it (the Farallon plate no longer exists here, at least at the surface). The sediment that was scraped from the Farallon plate was jammed into a trench in the bottom of the subduction zone. There it compressed into sandstone. The turbidity flows that were responsible for the deposit of Graywacke are basically an underwater landslide (often started by earthquakes). During most turbidity flows, the large sediment settles out of the water first then lighter to the finest sandstone and shale layers.
Graywacke is gray when it is fresh, but ages to a brown (as you can see). Graywacke differs from Sandstone in that the sediments vary dramatically in size and composition, making the rock look "dirty", especially in comparison to the relatively even texturing and look of sandstone.
Graywacke is deposted in one of two ways -- either as one massive turbidity flow or by several small ones. The texture of the rocks and coloring (based on sediments present) help us tell how many flows (and thus deposit originations) were involved in creating the formation of graywacke that we view. Sometimes, fracturing makes it LOOK like there are a lot of layers of graywacke. How can you tell the difference? The best way is chemical sampling! Otherwise, visual identifiers include DISTINCT coloring/texture denote several flows, while similar texture and simply seeing "dividing lines" tends to denote fracturing. So, how many turbidity flows are visible in front of you? Figure that out for the logging requirement!
This is my 41st earthcache "hide" and 100th "cache hide."
Congrads to geojammers and geoknits for FTF (First to Finish logging requirements) on 3/28/2010.
Thanks to Team SageFox for suggested edits to make this older earthcache "update" for the modern era of quality EC's.
Resources:
KRIS web -- (visit link)
Additional Hints
(No hints available.)
Treasures
You'll collect a digital Treasure from one of these collections when you find and log this geocache:
Loading Treasures