Sforno on Numbers 16:33/ספורנו על במדבר ט״ז:ל״ג

1ותכס עליהם הארץ, the Torah emphasises that this phenomenon was unlike an earthquake in which the fissures in the earth do not close again to wipe out any traces of what had occurred. Here, the earth looked as if nothing had happened after Korach and his fellow travelers had disappeared.