The Erosion of Mount Rushmore (with music)

Mount Rushmore wasn’t carved here by accident. The rock itself chose the monument. Those four faces

are carved into Harney Peak granite — one of the hardest, most stable rocks in North America.

This granite formed nearly 1.7 billion years ago, deep underground, long before dinosaurs

or even complex life. Granite cools slowly beneath the surface, creating tightly

locked crystals that resist cracking and erosion. That mattered. Softer rock would’ve

crumbled within decades. This granite can hold detail for thousands of years.

The sculptor, Gutzon Borglum, specifically chose this cliff because it faced southeast,

maximizing sunlight and minimizing water damage. But erosion hasn’t stopped.