A moving slope does not behave like a solid hill; it behaves like a river of debris. When rock, soil and broken trees start sliding, the whole surface becomes a conveyor belt driven by gravity. Anyone who runs straight downhill stays on that belt, matching its direction and often its speed, which keeps the person locked inside the fastest, thickest part of the flow.
The physics is closer to granular flow and fluid dynamics than to hiking. As material accelerates, shear stress concentrates in the central channel, where velocity and impact energy peak. Running downslope aligns your body with that high energy corridor. Moving diagonally, or even directly across the slope, changes the vector of your motion relative to the slide, increasing your lateral displacement and your odds of reaching slower edge zones where friction against fixed ground, boulders and vegetation is higher.
At the margins, the flow often thins, turbulence rises and local friction coefficients increase, which can create brief pockets where feet can grip instead of surf. Even small gains in lateral distance can shift you from a dense, high momentum core into a more diluted fringe, sharply reducing burial risk and impact forces. In that short window, survival is less about speed and more about escaping the main channel of moving earth.
