C) 30 miles is the correct answer
(I’m not sure but I think so)
Obsidian is volcanic glass compared to other igneous rocks , there’s also no proper crystallization compared to the other igneous rocks
The world is round not flat cause first look image your viewing a picture of earth actually the earth is not really round its a shape called an ellipsoid which is kind of squatters and fat plus the world is round cause of the force of gravity
