Sand Dune Arch was formed through a process of geological uplift and erosion acting on sandstone layers.
Understanding Sand Dune Arch Formation
The creation of Sand Dune Arch is a fascinating geological story that unfolds over millions of years. Here's how it happened:
- Uplift: Approximately 15 million years ago, the entire region began to rise. This tectonic activity elevated the land, bringing buried rock layers closer to the surface.
- Erosion: As the region was elevated, the softer sedimentary rocks lying on top of the Entrada Sandstone were gradually removed by erosion.
- Exposure of Entrada Sandstone: Once the overlying sedimentary rocks were gone, the Entrada Sandstone was exposed to the elements. This sandstone is a key ingredient in arch formation, as it is more resistant to erosion than surrounding rock, but it still contains bedding planes and fractures that allow for water infiltration and subsequent weathering.
- Erosional Forces: The exposed sandstone then came under attack from the forces of erosion – primarily wind and water. These forces selectively eroded the weaker parts of the sandstone layers and enlarged existing cracks and fissures.
- Water Erosion: Rainwater and snowmelt seep into fractures in the sandstone. As water freezes and thaws, it expands and contracts, causing the rock to crack further. This is a process called frost wedging. Over time, this repeated cycle can cause sections of rock to break off and erode.
- Wind Erosion: Wind carries small particles of sand that act as an abrasive. This sandblasting effect, over very long periods, further erodes the exposed rock, shaping it in unique and interesting formations.
- Arch Formation: The continued erosional processes eventually led to the formation of the arches we see today, including Sand Dune Arch. These arches are usually formed where the softer material between the fractures was eroded away, leaving a rock bridge.
Summary of the Formation Process:
| Step | Description |
|---|---|
| 1 | Region uplifts approximately 15 million years ago |
| 2 | Erosion removes softer sedimentary rocks above Entrada Sandstone. |
| 3 | Entrada Sandstone becomes exposed. |
| 4 | Erosional forces (wind and water) act on sandstone. |
| 5 | Arch is formed by the removal of softer materials. |
Additional Insights
- The unique shape and location of Sand Dune Arch is due to the specific way the erosional forces interacted with the different layers and weaknesses in the Entrada Sandstone.
- The arch formation is a slow process that takes place over thousands of years.
