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Green Top Series #5: It’s a Cliff EarthCache

Hidden : 05/23/2011
2 out of 5
3 out of 5

Size: Size:   other (other)

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Geocache Description:

To celebrate my 1,000th find, I've decided to hide a small series. There used to be a final, but it is no longer active.

This cache must be done on the beach. The listed coords are for those who choose to do this cache at high tide. If the tide is low I would suggest walking out toward the water and looking back to view the entire cliff in all its glory. Do not attempt at night or outside park hours.

It’s obvious that there’s a lot of history and geology in these cliffs, but what formed them and why does it look like it does today? There were actually a variety of factors that contributed to the formation of the cliff.

20,000 years ago, a large sheet of ice known as The Vashon Glacier spread across the northwest. This was not the first time this had happened; the mighty glacier had grown and shrunk throughout the last few million years. Through this process the glacier carved out the Puget Sound as well as many rivers and geologic formations in the areas close by.

The glacier covered what is now known as the Puget Sound, islands within the Puget Sound, and land between the Puget Sound and the Cascades. It stretched as far south as present day Olympia. The glacier brought with it tons sediment including gravel, mud, silt, sand, and clay. This glacier put a lot of pressure on the earth’s crust and even made it sink in a few places.

The hard part of the cliff at the bottom with all the ripples (one part is showing right next to given coordinates) was formed before the Vashon Glacier engulfed the northwest for its last time. During this time, the Puget Sound was a basin of many rivers and streams (that were formed by the glacier earlier on) that flowed north toward the Pacific Ocean. The ripple patterned formation on the cliff is clearly very old, and not much is showing on the outside of the cliff anymore. This is mainly because of the sediment above.

The mixture of minerals that The Vashon Glacier left behind is referred to by geologists as “glaciomarine drift.” Once the glacier left the northwest, the whole region was covered in this material. This is the loose grayish material that can be seen on the upper part of the cliff. This part of the cliff is weak, thus parts of the glaciomarine sediment have slid down the cliff over time, covering the old parts of the cliff and destroying the vegetation that grew in its path.

A lot of the beach area has been influenced by the cliff. There are a lot of clay particles that make up the beach and the ripples that never seem to flatten out. The clay particles came from the sediment that slid down the cliff and were spread by the waves of the Puget Sound. There are sand granules among the clay as well. These probably also came from the cliff.

This cache placement was approved by Discovery Park.
The park is open daily between the hours of 6:00am to 11:00pm.
The nearest parking can be found at Discovery park's south parking lot (N47 39.274 W 122 24.616)
To log this cache you must email me the answers to the following questions. If I do not receive your email within 3 days of your log, it may be deleted without notice.

1) What geological process is responsible for most of the bottom part of the cliff being covered up?

2) What material does the rippled part of the bottom of the cliff (appear) to be made of?

3) There are many spots where sediment has slid off the cliff, what can be seen crushed beneath it?

Optional: A picture of you/your group with the cliff in the backround.

June 27th 2011: Please don't venture too close to the bluffs! They're unstable and dangerous.

January 29th 2012: If you have fufilled the logging requirements and logged your find but NOT recieved the clue from me via email, please contact me for the clue.

January 4th, 2015: The final cache in the series has been archived. I will no longer be emailing the clue.

Additional Hints (No hints available.)