Whoops Crowtooth could feel that small collapse even through the air and for a moment he was almost alarmed. Had she managed to burry her head? No she seemed fine just a bit dirt covered. At the realisation he broke into chuckles shaking his head and rasping out;
"Hehe, yeah that can happen. You need to pack in the dirt around your tunnel as you dig so its stronger. See you hit a loose patch which can help digging but also cause cave ins. Poke your paw in before trying to dig and if it goes too deep or you feel it crumbling around your paw you found a cave in spot and disturbing it could cause a collapse. Small spots do this, larger ones or pulling a support root around such larger areas it can destroy an entire tunnel and force you to bolt for your life. Still its predictable and you can even tell where it'll collapse by where the tunnel roof sags and wheres softer and weaker and wheres more reenforced.
Wanna try again?"
He'd grab her some sticks to reenforce her digging if so but if she wanted to move on he'd do so and allow her to experiment on her own time.
@
Panda1440