Welcome to the Explore Batiquitos Lagoon Series!
This series, created with permission from and in correspondence with the Batiquitos Lagoon Foundation, invites you to discover the natural beauty, rich ecology, fascinating geology, and deep history of Batiquitos Lagoon. Each cache offers a chance to explore a unique feature of this vibrant coastal environment. Take your time, look around, and enjoy everything this special area has to offer.
This is an EarthCache, meaning there is no physical container at the posted coordinates!
Welcome to Batiquitos Lagoon
At Batiquitos Lagoon, you’ll find a fascinating example of sedimentary geology revealed in an exposed hillside. This EarthCache invites you to explore the dynamic processes of deposition, erosion, and layering seen in features like cross-bedding and unconsolidated sediments. These formations offer a snapshot of the area’s changing environments over time.
The Formation of Cross-Bedding and Sedimentary Layers
Cross-bedding forms in sedimentary rocks like sandstone when water or wind currents shift over time, depositing layers of sand at an angle to the horizontal. Each angled layer, or “set,” shows the direction of the flow at that moment, creating a pattern of slanted lines within the rock. This pattern often appears in river deposits, deltas, beaches, and deserts, where currents or wind constantly move loose material.
At Batiquitos Lagoon, the cross-bedded sandstone was originally deposited by moving water, likely in a fluvial or estuarine setting. Above this sandstone, you’ll notice a layer of unconsolidated soil and silt. These finer materials were deposited more recently by slower-moving water. Mixed into this upper layer are larger cobbles—rock fragments that could only be transported during high-energy events, such as floods. When the water slowed down, it dropped the heavier material, forming a layer rich with clasts of various sizes.
Geological Significance
The exposed sediments at Batiquitos Lagoon tell a story of ancient and modern depositional processes. Cross-bedding provides clues about the direction and energy of water flows, while the overlying unconsolidated materials speak to more recent flood events. This site demonstrates how Earth’s surface is constantly reshaped by both gradual and sudden forces, such as erosion, weather, and seasonal water surges.
Tasks for This EarthCache
To log this EarthCache, visit the site and complete the following tasks. Send me your answers via Geocaching or email.
- EarthCache Title: Include “EBL 25 - Cross-Bedding - GCB78QV” on the first line of your message.
- Examine the Cross-Bedding: Look closely at the sandstone layer. Can you identify any slanted layers or patterns? What direction do they appear to tilt?
- Theorize the Type: Using the diagram above as a reference, what specific type of cross-bedding do you think this is? Explain your reasoning based on what you observe.
- Observe the Sediment Layers Above: What do you notice about the material above the sandstone? Is it fine-grained, coarse, or mixed? Describe the types of rocks or sediments you see.
- Identify Weathering or Erosion: Do you observe any surface weathering, such as cracks, crumbling, or plant intrusion? What natural processes might be affecting the site today?
- Photo Evidence: In your log, attach a photo of yourself or a personal belonging with cross-bedding sandstone AND the yellow Batiquitos Lagoon Foundation sign post at the coordinates in the background. (Note: photos predating the publication of this EarthCache are not accepted.)