Disclaimer: This Earth Cache is ONLY accessible via a flotation device. However, there is no physical container to find, intead visit the location and complete the logging tasks below.
Materials Needed To Complete This Earth Cache: Floatation Device, Camera, GPS.
Welcome to the Newport Back Bay! This beautiful ecological reserve is not only a haven for wildlife but also a fantastic outdoor classroom for geology. The impressive cliffs that line the bay tell a story of millions of years of Earth's history, from ancient seas to modern erosion.
The Geological Story of the Back Bay
The cliffs you see are primarily composed of the Monterey Formation, a geological layer that stretches along much of coastal California. This formation is a true "time capsule." Approximately 15 million years ago, during the Miocene Epoch, this area was a deep, nutrient-rich ocean basin. Microscopic marine organisms with silica shells, like diatoms, thrived and then sank to the seafloor after they died. Over millions of years, these tiny skeletons accumulated into thick layers of sediment.
As more sediment piled on, the weight compressed the lower layers, and the silica in the diatom skeletons dissolved and re-precipitated, turning the soft sediment into hard, white diatomaceous shale and other siliceous rocks. This process is what created the distinct, light-colored strata that are so visible in the cliffs today. The Monterey Formation is also incredibly significant because it's a major source rock for much of California's oil. The organic material from the ancient marine life, under immense heat and pressure, transformed into hydrocarbons that are now trapped within the rock.
The Shaping of the Bay
The cliffs were not always exposed. Over time, tectonic forces uplifted this ancient seafloor. Then, during the Pleistocene Epoch (the "ice ages"), when global sea levels were much lower, the ancient Santa Ana River carved a deep canyon through this newly exposed land. As the climate warmed and glaciers melted, sea levels rose and flooded this canyon, creating the shallow estuary we now call the Back Bay.
The shaping of the bay continues today. The forces of erosion are constantly at work, wearing away the cliffs. While the river originally carved the canyon, it is now the tides and runoff that are slowly undercutting the base of the cliffs, causing the dramatic features you can see. The loose sediment at the base of the cliffs is evidence of this ongoing process.
Logging Requirements
To log this EarthCache, please answer the questions below by observing the geological features in the area. There is no physical container to find. Please send your answers to me via the Geocaching Message Center, or email within a reasonable amount of time after logging your find.
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Cache Idenitification: On the first line of the text in your answers include "Monterey Formation - Newport Back Bay - GCBCB49."
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Layers of Time: Observe the cliff face and describe at least two differences you see between two different layers (strata). For example, do they have different colors, textures, or thicknesses? What might have caused these differences in the depositional environment?
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The Power of Erosion: Look closely at the base of the cliff. How is the cliff face being eroded? What evidence of this erosion can you find in the surrounding area (e.g., at the base of the cliff or in the water)?
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Photo Evidence: Post a photo in your log, or send one to me in your answers with you or a Geocaching Related Item, with your flotation device in the photo.
Cited Works:
https://newportbay.org/how-was-the-back-bay-created/
https://www.ocparks.com/parks-trails/upper-newport-bay-nature-preserve/history
https://www.csulb.edu/geological-sciences/sedimentology-and-diagenesis-of-the-miocene-monterey-formation-of-coastal
https://npic.orst.edu/factsheets/degen.html