Logging Requirements
To log this EarthCache, visit the posted coordinates at the central canyon floor and answer the following questions based on your on-site observations. Please send your responses before logging your find to me via the Geocaching message center or email. And as always, please be respectful of the natural features while you're exploring.
- How many distinct sediment layers can you count?
- What colors, textures, and thicknesses do you notice in the layers, and what might that say about how each layer was deposited?
- Walk north about 40’-50’ along the canyon floor and observe both ends. Do the sediment features change? If so, describe what you notice.
To complete this EarthCache, please include a photo of yourself, your group, or a personal item at the posted coordinates with your log.
- The photo must be taken with the exposed walls in the background.
- Make sure your answers to the questions above are not visible in the photo.
Arkansas Little Grand Canyon
Located just beyond the dam and spillway at Lower White Oak Lake, this beautiful site offers a chance to see sedimentary rock layers up close. The rock layers here are part of the Cane River Formation, a geologic unit dating back to the Tertiary Period (approximately 66–23 million years ago). This formation records the dynamic shifts of ancient environments, from swamps and floodplains to shallow marine waters. As you stand on the central canyon floor, take a moment to look around at the walls of exposed rock. Each layer tells a part of the story of this landscape.
After exploring the canyon floor, take a short walk to the nearby spillway (trust me, you want to do this), where you can see water still at work reshaping the land. There’s also a nice 0.4-mile trail that loops around the Little Grand Canyon, giving you different views and plenty of photo opportunities. Note: A trail map provided by White Oak Lake State Park has been uploaded for reference.
Sediment Layers
Sediment layers form when bits of rock, sand, mud, and even organic materials like dead plants and animals are carried by wind, water, or ice and slowly settle in places like rivers, lakes, oceans, and deserts. Over time, these particles build up in flat layers called strata. Each layer acts like a time stamp, recording what the environment was like when it was formed. As more layers pile on top, the weight compresses the ones below, and minerals in groundwater help bind the sediments together, turning them into sedimentary rock.
The oldest layers are usually at the bottom, and the youngest at the top, a principle known as the law of superposition. By studying the thickness, color, grain size, and contents of these layers, geologists can figure out things like whether the area was once underwater, part of a river system, or exposed to wind like in a desert. For example, fine-grained, dark-colored layers might suggest deep, still water, while cross-bedded sandy layers might point to flowing rivers or shifting dunes.
Sometimes, sediment layers contain fossils, footprints, volcanic ash, or signs of floods and droughts. Changes between layers can show major events like climate shifts, sea-level changes, or even mass extinctions. Because of this, sediment layers act like pages in Earth’s history book, helping scientists understand how landscapes have changed, what kinds of life existed, and how the planet has evolved over millions of years.
Acknowledgments
This EarthCache was written based on GSA and Geocaching guidelines. Permission for this EarthCache was granted by Poison Springs State Forest. A very special thank you to the Office of the State Geologist and AllThingsEarthCache for their guidance and expertise in order to successfully create this EarthCache.