As an EarthCache, there is no 'container' to discover. Rather with this cache, you will discover something about the geology of the area. For more information go to www.earthcache.org YOU WILL NEED A SMALL MAGNET AND SOME VINEGAR for the logging requirements. A magnifying glass may be helpful too. LOGGING REQUIREMENTS: Send the answers to me through my geocaching profile. DO NOT post the answers to any logging requirements
1- Based on the information below and the sand particles in your hand, do you think that this sand is smooth or rough, small or big?
2- What do you think this sand came from and why? (see information below)
3-What color is the sand?
4- See how much (if any) magnetite there is in this sand, drop a magnet into the sand and remove it. Did any dark spects of rock stick to the magnet?
5-Reach down and grab a handful of the wet sand notice the the colors of the different layers as you pull your hand out. What colors do you see?
6- To discover if there are any shells or micro-skeletical remains in this sand, pour a very small amount of vinegar into the sand. If it bubbles - shells and micro-skeletical remains are present. DOES it bubble?
(1/2 tablespoon of sand mixed with 1/2 tablespooon of vinegar gives the most accurate results.)
7- Post a picture (optional) of your GPSr and/or yourself with your log that shows the lake in the background.
You may want to take a sample of sand home for the above experiments.
Lake Tahoe
About 2 million years ago, a shift in tectonic plates caused the Tahoe Basin to drop down between the Sierra crest to the west and the Carson range to the east. Volcanic activity, also caused by the tectonic shifts, led to expulsion of magma up through the faults, filling in gaps and damming the valley. Ten thousand years ago, at the time of the last ice age, individual glaciers formed at the area’s highest elevations, on the north, west and south ends of the Lake. Movement by the glaciers scoured out basins and formed Donner Lake, Emerald Bay on Lake Tahoe and Fallen Leaf Lake, which sits up and to the West of Lake Tahoe..
GEOLOGY:
Sand is a naturally occuring 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 feel gritty when rubbed between your fiingers!
Sand consists of rocks, crystals, shells and skeletical 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: quartz, feldspar, chlorite, gypsum, and possibly magnetite (see logging requirement).
SAND DEPOSITION & COMPOSITION:
Nine sand samples above represent nine different sand types. Row by row from left to right: 1. Glass sand from Kauai, Hawaii 2. Dune sand from the Gobi Desert, Mongolia 3. Quartz sand with green glauconite from Estonia 4. Volcanic sand with reddish weathered basalt from Maui, Hawaii 5. Biogenic coral sand from Molokai, Hawaii 6. Coral pink sand dunes from Utah 7. Volcanic glass sand from California 8. Garnet sand from Emerald Creek, Idaho 9. Olivine sand from Papakolea, Hawaii. Sand is transported by wind or water and deposited in the form of beaches, as is the case here, or dunes and sand bars.
The study of individual grains can reveal much historical and geological information as to the orgin and kind of transport of the grain. Sand that is RECENTLY weathered from larger rocks 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.
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 to see if this beach has these creatures in significant numbers sufficient to set off a vinegar 'reaction.')