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Crystal Cove State Park Beach Geology

By Merton Hill, PhD, Saddleback College
id_3909934
Rating: 5 out of 5 by EveryTrail members
Difficulty: Easy
Length: 1 miles
Duration: Less than 1 hour
Family Friendly

Overview:  Spectacular ocean panoramas and contorted rocky cliffs are yours to enjoy on this self-guided tour of the geology of Crystal Cove... more »

Tips:  Protect your park. Enjoy only trails designated by park maps and signs. Camping reservations are required.

Be prepared. Pack plenty... more »

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Points of Interest

1. Intro

Thank you for downloading the Crystal Cove Geology Guide by Dr. Merton Hill brought to you by Crystal Cove Alliance, the non-profit co-operating association for Crystal Cove State Park.

This Geologic Points of Interest guide takes you to the shore where the (locally) 12- to 6-million-year-old rocks of the Monterey Formation crop out.

The ocean... More

2. Sidewalk Cracks

Our first Point of Interest (POI) is along the south side of the Los Trancos parking lot. Observe the cracks in the sidewalk and adjoining asphalt pathway. Why are
they here?

Ground movement is the answer. But what kind? Faulting, clay soil expansion and contraction, mass wasting (the
downward movement of rocks or soil due to gravity – ranging... More

3. Urban Runoff

Why does the water run year round even long after the rainy season? Why does it commonly flood the tunnel under Pacific Coast Highway just ahead?

The answer is urban runoff. This is water from
homeowners’ landscape, city streets, and the golf course. Despite the constant flow, runoff is now much reduced since the installation in 2007 of an... More

4. Igneous Rocks

Just before the tunnel you will see hard crystalline boulders embedded in the concrete. These igneous rocks (formed from molten magma) are not natural to the park but were imported to minimize erosion.

Nonetheless, look closely at their grain size and color. On this side of the tunnel, most are coarse grained (you can see individual crystals... More

5. Magnetite in the Sand

At some places in the sand you will see streaks of fine black particles. Without really analyzing it, some people conclude these are crude oil or tar. However, if you run a magnet through the streaks, the particles will stick.

The black needles are the mineral magnetite, a component of ocean floor basaltic (volcanic) igneous rock. These needles ... More

6. Meandering "River" and Migrating Ripple Marks

Unlike mountain streams which run quickly and fairly straight and produce V-shaped canyons, streams in areas of low gradient (slope) run slowly and meander (make snake-like curves in their beds) and produce wide flat flood plains. Here you see a scale model of the latter. The outside walls of the bends are called cut banks. As time goes by the... More

7. Monterey Formation and Mass Wasting

Walking south you see the last historic cottage. The “Beaches Cottage” was featured in a 1988 film starring Bette Midler, Barbara Hershey and John Heard. Despite its fame and photogenic character, it was one of the last Crystal Cove cottages to be restored. Why? Because mass wasting of an unstable cliff of Monterey Formation in its back and side... More

8. Concretions in the Monterey Formation

Visitors to Crystal Cove often ask about the hamburger bun-shaped or UFO shaped rock “formations” littering the
beach especially in the vicinity of the Beaches Cottage. These features range in size from a few inches to more than 12 feet in diameter. Look carefully in the cliff
towering over the side yard of the cottage.

You will see several... More

9. 120,000 Year-Old Fossils

Walk further south and you will see these shells embedded in sandstone on the beach adjacent to the cliffs. You may not give them a second thought. Although to the casual observer they appear modern, they are about 120,000 years old. This seems a great age to humans, who typically consider time in hours, days, weeks, years, and human lifetimes. To... More

10. Columnar Jointing in Volcanic Rock

At the southern-most point of Crystal Cove you will find cliffs of andesite (a fine-grained igneous rock which cooled from lava at or near Earth’s surface). Geologists term this kind of rock volcanic as opposed to coarse-grained plutonic rock which cooled deep in Earth’s crust.

Here the lava cooled quickly and produced well-defined prismatic... More

11. Recumbant Folds

The severely folded Monterey beds exposed in the cliff at the north end of the beach at Crystal Cove are textbook examples of recumbent folds. These layers are so tightly contorted that it is hard to imagine solid rock bending like this – even under high heat and pressure. Despite the extreme folding, no visible faults are associated with this... More

12. Caves and Oil

You may have already noticed black oily patches on some of the rocks or the beach sand. Be careful with your
identification. Some of the spots may actually be “tar spot algae” or magnetite. On the other hand, some may indeed be petroleum.

On a clear day you can see oil platforms off shore Newport and Huntington Beaches. These platforms may host
... More

13. Newport Jetty Overlook

From the beach climb the steps up to the bluff top and follow the path left to the Newport Jetty overlook. When looking north toward Corona del Mar, you will see
the Monterey cropping out all along the beach. Now observe the rocks exposed on the inland side of the trail. They appear very similar to Monterey Formation rocks rising out of the beach ... More

14. Conclusion

Thank you for taking the Crystal Cove State Park Geology Tour. We hope you have gained some knowledge and had fun in the process! This guide was written by Dr. Merton Hill, Saddleback College. Editing & images provided by Dr. Annlia Hill, UC Irvine with the assistance of Crystal Cove State Park personnel, and brought to you by Crystal Cove... More