This is one of just a hand full of earth caches at the Laguna Hills Community Center. This one, however, is located outside and is available to visit 24/7. If you look closely along the south side of the stairs, you'll be able to see inserts of the local limestone. Large fossils, some a few inches long, are still intact in its original state exposed to the elements. Let's explain the geology behind limestone and the fossils it contains.
Limestone is formed from the decay of marine life. When they die, they sink to the bottom. Now, all living things must have phosphorous as it makes up DNA. When the animal dies, the phosphorus decays as well and over time, forms a hard layer of rock we know as limestone. Limestone gets its distinctive color from the calcium in the rock from other parts of decaying organic mater. Sea shells are almost entirely made of calcium carbonate (CaCO3). Over millions of years, this limestone has lifted out of the ocean from below sea level, to this site at a rate of about two millimeters every year. The limestone you see before you was taken here when the site was being excavated for the community center. How cool is that?!?
Limestone forms from phosphorus rich dead organic matter that falls to the bottom of lakes and oceans. Overtime, limestone is brought to the surface and looks like this:
So how did this limestone get a few hundred feet above sea level and why is it so far inland? Well, the California Coastal Ranges used to be underwater about five million years ago. Due to the many faults in Southern California, some of these areas have literally lifted out of the ocean. This is due to the fact that faults create tension on the land between other faults. There is the Newport-Inglewood fault just off shore of Laguna Beach which creates tension between the Elsinore Fault near Lake Elsinore. The small hills in south Orange County are due to the dormant Christanos Fault. Because oceanic crust is thiner, it's the first to give way creating mountains and uplifting the land. That's how this limestone came to this location, in the hills of Laguna.
TO LOG A FIND ON THIS CACHE YOU MUST GIVE ME THE CORECT ANSWERS BEFORE YOU LOG A FIND. YOU CAN CONTACT ME THROUGH MY EMAIL OR THE GEOCACHING MESSAGE CENTER. ANY INCORRECT ANSWERS WILL RESULT IN A DELETED LOG
1. "Steps Through Time" on the first line of your email AND list all geocaching names of your party so I can match your answers to them.
2. As you walk down the stairs towards the community center, count the number of individual limestone inclusions that are part of the wall.
3. Of these inclusions, how many actually contain fossils?
4. Describe the (a) textures, (b) colors, (c) average sizes of the limestone ROCKS at this location.
5. Describe the (a) textures, (b) colors, (c) average sizes of the limestone FOSSILS at this location.
6. What type(s) of fossils are visible here? How can you tell?
7. Explain the erosion process here AND how it has effect the limestone and fossils within it. Do you see any evidence of rusting or corrosion? If so, explain what you see and why it's occurring. If not, explain why you think nothing is happening.
Works Cited
http://geology.com/rocks/limestone.shtml
http://www.sharkbay.org/geological_foundations.aspx