South Fork Stilly~ A river on a Rampage 🌎 EarthCache
Hidden : 10/11/2019
Difficulty:
2 out of 5
Terrain:
1.5 out of 5

Size: Size: other (other)

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Geocache Description:



For purposes of logging this cache you must answer the following questions and take a picture of you or a personal item with the falls : Note: Your answers will vary depending on what time of the year you visit.
1) Estimate the size of the largest pothole here that you can observe? Do you think it was formed originally from one pothole or two that became one? How did you derive your answer?
2) Are the potholes located on the north, south or both sides of the river? What caused them to be located this way?
3) There are three drops that make up the falls. What is the total vertical distance of the three drops combined. (A sign to the south will help you answer this question!)


An earthcache is the magical combination of geocaching and geological discovery. They vary greatly from traditional geocaches in that there is NO PHYSICAL CONTAINER! Once at the Earth Cache site, take in the scenery, the geological marvels or oddities, and read the cache description. You will likely be asked to answer some questions about the site and optionally take a picture. You can email the cache owner or use the Message Center to send answers to the required questions. Please don’t be intimidated about answering the questions. They are not graded and were meant to enrich your visit, open your eyes and provide you with new knowledge and insights about the location. Most importantly have fun!

This earthcache is located on Washington Department of Fish and Wildlife property and placed with permission.

This earthcache brings you to the Granite Falls Water fall and fish ladder located on the South Fork of the Stillaguamish River. The fish ladder that runs along the edge of the river doubles as a viewing platform. From here you can appreciate the incredible power these falls have generated over the years. Spring flows through this narrow section of river are thunderous, and the falls become a turbulent stretch of thrashing whitewater. If you visit at lower flows you'll see the evidence of this power in the riverbed's sculpted holes in the granite called potholes. A pothole is a circular or cylindrical hole in the riverbed which is produced by force of water and abrasion. A pothole is formed when a circular current of water carrying small pebbles and sediment begins to wear away a rock surface. They’re found in the upper course of a river where it has enough potential energy to erode vertically and its flow is turbulent. Sometimes, two potholes join to create an even larger pothole. In the upper course of a river, its load is large and mainly transported by traction along the river bed. When flowing water encounters bedload, it is forced over it and downcuts behind the bedload in swirling eddie currents. The force of water and the sediment it carries is greater than the resistance of the rock. Once the process has begun, it continues and the rock in that location continues to erode away. Geologists associate potholes with large volumes of very turbulent water.

Solid bodies of rock resist the erosive power of water more than sediments or rocks with lots of fractures. Contrasts in the resistance of rock often produce significant vertical changes in channel elevations, called knickpoints, where waterfalls and rapids form. The resistant rock at Granite Falls is a small body of old granite that remains stubbornly elevated above its weaker downstream neighbor, producing a substantial drop in vertical elevation. For the upper knickzone, waterfalls align with bands, of harder rock exposed on adjacent hillslopes, and between waterfalls,the channel is mantled by large boulders. The middle knickzone shows evidence for both fast and slow knickzone retreat.



EDUCATIONAL LOGGING REQUIREMENTS

In order to substantiate your visit and comply with the educational requirement for Earth Caches you have to submit your answers to the following questions to the cache developers via their profile. Please post your picture with the falls with your log.
For purposes of logging this cache you must take a picture of you or a personal item with the falls and answer the following questions.
1) Estimate the size of the largest pothole here that you can observe? Do you think it was formed originally from one pothole or two that became one? How did you derive your answer?
2) Are the potholes located on the north, south or both sides of the river? What caused them to be located this way?
3) There are three drops that make up the falls. What is the total vertical distance of the three combined. (A sign to the south will help you answer this question!)


Resources:
https://www.alevelgeography.com/pot-holes/
https://geographyas.info/rivers/river-landforms/
https://pages.mtu.edu/~raman/SilverI/The_Fault/Potholes.html
https://en.wikipedia.org/wiki/Pothole_(landform)

Additional Hints (Decrypt)

Gur arneol fvta jvyy uryc sbe dhrfgvba #3.

Decryption Key

A|B|C|D|E|F|G|H|I|J|K|L|M
-------------------------
N|O|P|Q|R|S|T|U|V|W|X|Y|Z

(letter above equals below, and vice versa)


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