Are they talking about landslides from steep slopes here, or is gravity sliding different?

I recently went to Scotland and got to visit Siccar Point, which is where James Hutton discovered a prime example of uniformitarianism. It is an angular unconformity, called Hutton's Unconformity, showing how the vertical beds were deposited, tilted, and eroded before the horizontal layers were deposited.

I looked up what he discovered from these experiments, and he found that friction is proportional to the load applied to the surface.