Answer:
The type of weathering that occurs is abrasion.
Step-by-step explanation:
Iguazu Falls are one of the highest waterfalls in the world and the biggest waterfall system in the world. The amount of water that falls down these waterfalls is enormous, and that combined with the height gives the water a lot of power. The water is carrying huge amounts of pebbles, rocks, the debris of all sorts and sizes, and they combined with the water manage to erode the bedrock.
As the water carries all of the material with it, it scratches the surface of the bedrock, and as it does it gradually makes the surface of the bedrock smooth. At the waterfalls themselves, the power with which the water and the material it carries are much bigger so they manage to create a very deep caldron-like hole in the bedrock below the waterfall, and plus smoothens its surface.