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San Lorenzo River Lagoon (Santa Cruz)

A cache by PathfinderMark Send Message to Owner Message this owner
Hidden : 09/28/2010
1.5 out of 5
2 out of 5

Size: Size:   not chosen (not chosen)

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Geocache Description:

As an earthcache, there is no “box” or “container” to discover. Rather, with this cache, you discover something about the geology of the area. For more info, consult

Parking is DIFFICULT throughout the area. Fee parking is available at the Boardwalk (.4 mile walk away) or there is metered parking in nearby lots and curbside. I would suggest doing this earthcache early before the crowds arrive!

The Earthcache:
From this location atop the bluff overlooking The Boardwalk in Santa Cruz, you can see the mouth of the San Lorenzo River as it dumps into the Bay.
Part of your task here is to observe what you see, so that as earthcachers, we can together "watch" for the seasonal changes in the mouth of the river.

Logging Requirements:
Send me a message via my geocaching profile for #1-#2, #4 (if you don't just upload a photo with your log #5).

With your log, list your observations for #3

1. List the name of the Earthcache and the number of people in your group.

2. Fill in the blank from the information panel near listed cords:

"Watch for seasonal changes as _______ action in late spring and summer builds a sandbar that closes the mouth of the river. By summer, a_______ ________ is formed."

3. POST WITH YOUR LOG: List the season (Spring, Summer, Autumn, Winter) when you visited and whether there was a sandbar and/or lagoon. Estimate the LENGTH of either of those present at the time of your visit.

4. To prove you were here, and in lieu of a photo, measure to the nearest cm the length of the Steelhead pictured on the information panel. You may do #5 instead if you so choose.

5. (optional) Take a photo of yourself with the mouth of the San Lorenzo River visible in the background or pictures that illustrate the status of the lagoon at your visit (#3).

Congrads to peigimccann for FTF (First to Finish logging requirements)

PLEASE LOG YOUR FIND. I will ONLY contact you IF it appears you have failed to meet the logging requirements.


Sanbars (spits) are a form of sedimentation that happen in this area as a result of ocean current and the river inlet. As the tides change in the spring and summer, and the spring floods bring down sediment from the California mountains, the combination creates a large "pile" that is elongated in shape that eventually cuts off the river from DIRECT access to the ocean. This "pile" is called a sandbar or sand spit. Sandbars can vary in size from a few meters to several miles in length. In fact, in many coastal areas, barrier islands form, that in reality are large sandbars where the "top" is now above the tide and thus can support plant life and habitat. However, in this instance the sandbar is seasonal and is greatly affected by the amount of wave action and river sedimentation. During the summer, the water from the river is diverted into a "pond" along the ocean's edge, called a lagoon.

If one were able to walk on the sandbar (there are steps down to the beach nearby), one would be able to determine the comparative size of the wave and the speed of the river when deposition happened, since the faster and harder the waves and river current, the courser (larger) the sediment sand/gravel/pebbles/rocks would be. If you decide to walk the beach when the sandbar is present, enjoy discovering this geologic feature!

(Tidal) Lagoons are bodies of water at least partially cut off from the ocean. They are often fed by freshwater sources, such as San Lorenzo River, yet contain brackish water since the ocean either seeps through the sandy floor or splashing in during high tides.

Because Lagoons are protected from the rough surf of the open ocean, they provide wonderful habitats for birds, fish, and grasses.

Steelhead Haven:
Steelhead need food, clear water, and a "safe neighborhood" to "raise their families." In this lagoon they have fresh water, protection from predators, and plenty of food for growth. Seasonally, the lagoon provides a habitat (home) for young Steelhead to thrive. Obviously, since the lagoon is on a public beach near a very popular tourist attraction, one could argue about the protection of this habitat, though signs and other deterrents may discourage some who would otherwise disturb the young fish.

Steelhead face some significant dangers at this lagoon. Pollution from the river runoff can fill their safe home with toxic levels of household chemicals. People swimming, fishing, or in other ways disturbing their fragile, though very public habitat, can cause population numbers to plummet rapidly. Please be eco-conscious when completing this earthcache!

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