 It doesn't need much to nudge it into action. If you have your palms pushed together with a sheer couple set up between them, it's ready to fail. And somebody comes and bumps your elbow, it's going to slip. That's right. It doesn't take much. If you had a dump truck with the sand in there filled up at the angle of repose, about 34 degrees, and it's all tilted up but it isn't sliding yet, and say a fellow on a motorcycle hits it from the side.