We often think that fossils are rare finds in only the most exotic locations but not close to where we live.
You will get to observe fossils that were actually part of the everyday landscape in the Laguna Hills area not so very long ago (in earth years, not human years).
Many of us have possibly passed the Laguna Hills Community Center on numerous occasions but never went inside to see the interesting fossil exhibit. If you complete this Earthcache activity, you will get the opportunity to find out why there is such a wide diversity of fossils in this exhibit.
The Community Center is open Mon through Sat, 8:00am to 10:00pm and Sun , 12:00 pm to 6:00pm. Additionally, they offer a free docent led fossil tour of their exhibits on the first Saturday of each month. To confirm the next tour and to make your reservation you may call 949-707-2692.
Background:
Lets begin by reviewing some things about fossils.
Fossils are the remains or impressions of ancient life both plant and animal. They range in size from microscopic structures to dinosaur skeletons. In order for fossils to be found, the previous living plant or animal must have been in an environment that was favorable to its growth and later it must provide favorable conditions needed for its preservation.
Two conditions are almost always present:
1. The possession of hard parts, either internal or external, such as bones, teeth, scales, shells,, and wood. These parts remain after the rest of the organism has decayed.
2. Quick burial of the dead organism so that protection is given against weathering, bacterial action, and scavengers.
Nature provides many situations that protect dead animals and plants from destruction. By far the most important environment for the preservation of fossils is marine sediment and fresh-water sediment. The dead remains of many sea or land animals, are covered by rapidly accumulating sediment in ocean basins or in channels, floodplains, and deltas of streams on land.
Methods of fossilization are varied but a common method is when organic material is replaced by inorganic material so that the form of the organism is preserved.
Petrification is the process of turning the hard parts of the organism into stone. "Replacement" is one method of petrification that occurs when mineral matter from ground water is substituted for the original organic substance. Every detail of the internal structure may be delicately recorded or only the outer shape may be preserved.
Dead sea organisms that have sunk to the bottom are quickly covered with sediment. As the sediment becomes thicker and heavier, the structure is embedded within the sediment which eventually becomes stone. The structure can disappear if it is dissolved by ground water thus creating a mold (an empty space that has the exact shape of the prior organism). If a natural mold is later filled with mineral matter, a natural CAST (mineral material in the shape of the original organism) is produced.
The earth's surface is subject to constant change. Areas formerly occupied by shallow seas have become mountains or vice versa, Any one place may have been a suitable environment for fossils to accumulate during several different times in its long history, but it will not have remained so continuously.
The City of Laguna Hills has been built over some of the richest deposits of fossil-bearing sediments in the United States. These strata represent over 17 million years of prehistory from marine incursions to coastal emergence and the formation of today’s hills and valleys.
Over the years this has led to a number of paleontological discoveries at various sites throughout the city as well as the site of this Earthcache.
Today in Laguna Hills you may be standing in a building, on a sidewalk, in a park, or waiting for the traffic light to change---but let's explore what the environment was like in this part of Orange County before we got here.
There have been three major paleo-environmental changes occurring in this region spread throughout the timeline of this fossil exhibit. While you are here, notice the interesting wall murals painted by John Iwerks that depict the changing environment over this time span.
SHALLOW TROPICAL BAY ENVIORNMENT:
Seventeen million years ago had much of Orange County covered under a shallow tropical bay. Fossils of tropical fish, sharks turtles, clams, tube worms, marine mammals, and distinctive large scallops or pecten shells were abundant. There was a mountainous peninsula to the southwest and a rolling semi-arid plain formed the northeastern shoreline of the bay.
DEEP SEA ENVIRONMENT:
Starting about sixteen million years ago the shore began to sink and became a wide seaway. There were deep seas covering all of this area and including the LA Basin area. The depth of the ocean where you are standing was estimated to be two miles deep. Deep sea sediments extended under Laguna Hills High School and the City of Laguna Woods. The marine fossils of this environment included whales, crocodiles, as well as fish and sharks.
Over millions of years the sea floor began to rise. The emerging shore presented a home for primitive sea lions, shore birds, and many mollusk varieties. Fossils of these animals have been collected from the silt and sands of Nellie Gail Ranch.
ICE AGE / GRASSY SAVANNA ENVIRONMENT:
The tectonic activity continued to lift the landscape for an additional five million years, gradually changing the landscape to wooded hills and grassy savannas. Beginning about 1.8 million ago the ice age began. In this environment saber-toothed cats, mammoths, mastodants, giant sloths, bison, horses, camels, and condors were present.
Today in Laguna Hills (outside of urban development) the environment has changed to dry grasslands and rolling hills. We don't see many of the same animals that lived here from earth history, but we can see their fossil record in this exhibit.
Logging requirements:
To qualify for this Earthcache, each person should answer the following questions and send your answers to me. Record the title line of the e-mail as GC7HMB1--Fossils Under Your Feet.
Refer to the following diagram showing five display cases. As you enter the exhibit, case number 1 is on your right. Question numbers refer to that cabinet number. Use one of the three mentioned environments for part of your answer.
1. In what geological environment did this animal live?
2. In what geological environment did these animals live? Compare the fossil teeth of animals in this collection: Which animal was most likely the fiercest predator?
3. In what geological environment did this animal live? While estimating the size of the two largest bones of this animal: How do they compare to the same bones in your body?
4. In what geological environment did these animals live? What method of fossilization would you guess produced the "clam" fossils?
5. In what geological environment did these animals live?
6. Why is there such a wide diversity of fossil types in the entire exhibit of five cabinets?
In addition to the fossils in the Community Center room, check out the following links of additional interesting locations or pictures from the Laguna Hills website.
"Costeau Park"
"Fossil Reef Park"
"Fossil Discoveries"
Works Cited: https://www.ci.laguna-hills.ca.us/199/Public-Art-Fossil-Archive, https://www.ci.laguna-hills.ca.us/200/Fossil-Discoveries