When I opened world, Mountain randomly generates | I have found no reports like this

I spawned in my world, I noticed a mountain was in front of me, and when I got a closer look, there was a big gap in the ground, showing the void. I have no idea how this happened,but I did notice that it took longer to load my word than usual (about 15-20 seconds longer). If there is any way to fix this, please comment below. I have provided some screenshots of what happened below.

UPDATE: \/

I explored around the mountain, and I noticed it did not split the world in half, but it was a large square of land (~300 x ~300 blocks). I noticed more chunks nearby it.

Thank you.