So I entered into my minecraft world, and it looked like the ground has risen up, it cuts trees in half, destroys things I've built. It appears everywhere in my world! Pls help!

This isusue is because you closed world and then exit game and quickly made new world.
This isnt crucial bug howewer mojang shud fix that. i can confirm it is hapening.

Just wait a bit before swiching/generating new worlds and you will be fine.