Ancient Pictures EarthCache
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
You need to bring the following with you to this earthcache: a magnifying glass and a piece of steel (a nail or pocket knife works great!)
Long before humans walked the earth, before birds covered the sky, before dinosaurs roamed the earth, ancient art was being formed. You are visiting such a place that has been buried for millions of years
.
Before the North American tectonic plate started its movement westward and collided with Juan de Fuca plate, this part of the continent was underwater. Scientists believe that volcanoes around the world contributed ash and dust in the atmosphere around the northern hemisphere. The continents at that time were subjected to glaciers grinding away rock and mountains. Weathering and erosion moved sediments to the sea, where they settled to the bottom.
Moving water moves sediments. The faster water moves, the more and larger sediments get moved. The slower water moves, less and smaller sediments get carried. When rivers and creeks enter a lake or an ocean, the larger particles drop out first, and smaller and smaller pieces get carried farther and farther into the body of water until they finally settle to the bottom. Gravel is particles over 2 mm diameter and each particle is easily seen with the naked eye. Sand is from .1 mm to 2 mm individual grains can be seen with the naked eye. Silt is from .1 mm to .01 mm and individual grains can be seen with a magnifying glass. Clay particles are smaller than .01 mm and cannot be seen without equipment.
Cross bedding is a feature where dune like structures are created on the ocean and lake bottoms. Heavier particles are settled first, then lighter particles. This process is repeated over and over and over, creating bands and striations in the deposited sediments. For more information, click here.
http://www.indiana.edu/~geol105/images/gaia_chapter_5/sedimentary_structures.htm
The sea slowly filled in, adding more sediments on top. Pressure built up, starting the process of creating sedimentary rocks.
When the North American plate started to collide with the Juan de Fuca plate, the Juan de Fuca plate was pushed under the North American. The sea floor started to bend and buckle. The cross bedding now started to twist and fold. The sea bed was lifted and what was once buried below the sea is now a mighty, growing mountain range. This process has been happening for millions of years.
When you get to GZ, pull off the road onto the parking areas. To log this Earthcache, please email the following:
- First line should be Ancient Pictures: GC3TCX0
- Locate an example of picture sandstone. Use your magnifying glass. Look at the individual grains making the rock. Does this rock seem to be made from gravel, sand, silt or clay or a combination of the above? How did you make this determination?
- Your fingernail has a hardness of 2. A piece of steel such as the nail or pocketknife you brought has a hardness of 5.5. Estimate the hardness of the rock by scratching with your fingernail and the piece of steel. Which scratches it easier?
- The sandstone pictures were created by cross bedding. How do you think the fantastic patters were created after the cross bedding.
- (optional, but would be great!) Take a picture of an example of the picture sandstone and post it with your log. If you would like to be included, that would be even better.
Send your answers to:
markcase@aol.com
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