Why the Appalachian Mountains Are Wearing Away: Erosion Over Eons

Forces That Shape the Ancient Appalachians

The Appalachians, once as high as the Himalayas, have been eroding for over 200 million years. Key factors:

1. Water Erosion (Primary Driver)

• Rainwater seeps into cracks, freezes, expands (frost wedging)
• Rivers and streams (e.g., Susquehanna, Ohio) carve valleys, transport sediment

2. Glacial Erosion (Pleistocene Ice Ages)

• Glaciers scoured northern sections, creating U-shaped valleys, cirques
• Glacial weight depressed crust; rebound continues today

3. Wind Erosion

Abrasive sand/dust particles wear exposed rock surfaces, especially at high elevations.

4. Tectonic Uplift & Faulting

• Ancient collision faults reactivate, causing differential uplift/subsidence
• Creates new relief for erosion to attack

5. Human Acceleration

• Mining (mountaintop removal), logging, construction remove vegetation, destabilize slopes
• Increases sedimentation in streams

The combined effect: slow, relentless reduction of elevation, rounding of peaks, and filling of basins—classic old-age topography.