Greg is fearful of visiting the dentist, but he is also fearful of having his teeth decay if he does not visit the dentist. he is experiencing a(n) conflict.

avoidance - avoidance

Explanation:

An avoidance - avoidance conflict is characterized by a situation that you are afraid of happening, but in order for it not to happen, you will need another situation that also causes fear in you. It is a situation where the expression "if you run the animal will catch you and if you stay the animal will eat you"  applies with mastery.

Imagine you have a mega toothache. Now also imagine that you hate (are terrified of) going to the dentist. Which one do you choose? Imagine you broke that super valuable piece of your mother. You can tell her or not tell her. As long as you don't count, you can't stop thinking about it, every time your mother moves that corner of the play, you get cold. When your mother finds out, she will finish you. That's why dodge-dodge situations are so annoying.

it cools slower in the earth meaning the crystals have more time to form than lava on the surface