After reading the new chapter. Is Obito's ability to move through earth due to his Kamui or the power of hashirama's body? Since he has no requirement to eat or anything like that just like the Zetsu's, and they are able to move through earth.
wombat is right it is his kamui that allows him to
do that. Madara said that the rocks should have
crushed his entire body and not just half but i
believe that at the last second Obito prolly used
kamui on accident and phased into where Madara