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Monterey Sandy Sediments Earthcache

A cache by PathfinderMark Send Message to Owner Message this owner
Hidden : 11/06/2009
1.5 out of 5
1.5 out of 5

Size: Size: not chosen (not chosen)

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Geocache Description:

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

The southern part of Monterey Bay contains several small sedimentary beaches. The origin of this sand is the puzzle for this earthcache!

You can reach this location by car via Ocean View Blvd or via bike/walk along the Monterey Bay Coastal Trail. It is near a popular beach @ Lover’s Point. In orde to complete the logging requirements YOU WILL NEED: 1) A SMALL MAGNET and 2) A SMALL AMOUNT OF VINEGAR (or you can collect some sand and do the experiment in the comfort of your home. (see logging requirements)!

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles. As the term is used by geologists - sand particles range in diameter from 62.5 micrometers to 2 millimeters. Sand feels gritty when rubbed between your fingers!

Sand consists of rocks, crystals, shells and skeletal remains of organisms, eroded over time by the wind and water. Sand compositions can vary greatly from one area of the world to another.

The most common constituent of sand is silica, also called silicon dioxide, usually in the form of quartz. The composition of sand is highly variable, depending on the local rock sources and conditions. Sands in the area contain varying amounts of many of the following: Hornblende, Augite, Jadite, Gypsum, and possibly even Magnetite (see logging requirement below). Sands rich in magnetite are dark to black in color. Because Granite is present in the area, feldspar and Formica are also likely present.

Sand Deposition & Composition:
Sand is transported by wind or water and deposited in the form of beaches, dunes, and sand bars.

The study of individual grains can reveal much historical and geological information as to the origin and kind of transport of the grain. Quartz sand that is recently weathered from granite quartz crystals will be angular and be of drastically different sizes. It will feel rough to the touch. By contrast, sand that is transported long distances by water or wind will be rounded.

This sandy beach is part of an alluvium area that covers the area around the Monterey Bay. It formed as a result of the movement of area faults and thus the continental shelf “grinding” the granite as the oceanic plate was submerged. In addition wind and/or water has influenced the placement and content of the beach (you decide, based on logging requirement #2).

Of course, in most cases, there are not simply rock grains in the sand on a beach. Most beaches are part of a complex ecosystem with a large variety of mono-cellular to multi-cellular microscopic “shell-like” creatures as well as monopod and gastropods (shells in the typical sense of the word). All of these living organisms have a calcium-based bone structure, which can be absorbed / broken down with vinegar (see logging requirement below to see if this beach has these creatures in significant numbers sufficient to set off a vinegar “reaction.”)
Logging Requirements:
Send the answers to #1-#5 to me through my geocaching profile.

1. List the name "GC20AP8 Monteray Sandy Sediments Earthcache” in the first line of your email. Also, list the number of people in your group.
2. Based on the descriptions above and the sand particles in your hand, do you think that this sand traveled a long distance or a short distance? That is, did it come from the submerged canyon in the bay (nearby) or from fault action along the San Andreas fault, or other further away action?
3. Do you think this sand was primarily eroded by water or wind? Why?
4. To discover how much (if any) magnetite there is in this sand, drop a magnet into the sand and remove it. Did any dark specs of rock stick to the magnet?
5. To discover if there are shells or micro-skeletal remains in this sand pour a very small amount of vinegar onto the sand. If it bubbles – shells and micro-skeletal remains are present. Does it bubble?
6. (Per current 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 indicates your visit to the GZ. DO NOT show any of the pertinent information panels in your picture or your log may be deleted. If you are "anti picture" then tell me the PAINT COLOR of the snack cafe building near the coordinates.

I will only respond if you have incomplete logging requirements. Go ahead and log your cache

Congrads to RoadHazard386 on FTF (First To Finish logging requirements)

Roadside Geology of Northern and Central California. Davil Alt and Donald W. Hyndman.
Recent Sediments of Monteray Bay. T. Yancey. (visit link)

Additional Hints (No hints available.)

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