The photo collage shows that the distance travelled by the rock between each frame is approximately 2-3 m (assuming the rock size estimation of 8-20 cm is corre

The photo collage shows that the distance travelled by the rock between each frame is approximately 2-3 m (assuming the rock size estimation of 8-20 cm is correct) . If the GoPro recorded at 60 fps, it means the rock's speed was 120-180 m/s, which is very plausible!