You mean to tell me that you think a 155' by 124' object, weighing in at 255,000 lbs (175 tons) slamming into the ground at 500 MPH would leave a hole only as big and as deep as the average back yard swimming pool? If you think Flight 93 crashed with no outside help, that's what you must conclude.

Don't obfuscate matter with ground density or humidity or whatever. Any intact aircraft that big, that heavy, moving that fast would gouge a massive crater even in the hardest concrete.

It's common sense.