Rock steps are formed by glacial erosion acting on bedrock with varying resistance.
Here's a breakdown of the process:
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Variable Bedrock Resistance: Glaciated areas often have bedrock composed of different rock types with varying resistance to erosion. Some rock types, like granite or quartzite, are harder and more resistant, while others, like shale or sandstone, are softer and more easily eroded.
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Glacial Erosion Processes: Glaciers erode the landscape through two primary processes:
- Abrasion: The glacier, embedded with rocks and debris, scrapes and polishes the bedrock surface as it moves. This is similar to sandpapering.
- Plucking: Meltwater seeps into cracks and fractures in the bedrock. When this water freezes, it expands, breaking off pieces of rock that are then incorporated into the glacier.
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Differential Erosion: Because of the varying bedrock resistance, the glacier erodes the softer rock more quickly than the harder rock. The harder, more resistant rock protrudes above the surrounding landscape.
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Formation of Steps: Over time, this differential erosion results in a series of step-like formations. The resistant rock forms the "riser" of the step, while the eroded area in front of it forms the "tread."
In summary, rock steps are the result of glacial erosion processes (abrasion and plucking) acting on bedrock of varying resistance. The more resistant rock remains higher, creating the step-like appearance.
