Mass wasting is when big chunks of earth and rock move down a hill or a slope. Think about playing with sand at the beach. If you make a big pile of sand and then poke at the bottom of the pile, some of the sand might start to slide down. Mass wasting is like that, but with dirt, rocks, and even big boulders!
This can happen in different ways, such as landslides, rockfalls, mudflows, and even avalanches. Sometimes, it's because the ground gets too wet and heavy, like after a lot of rain. Other times, it's because of earthquakes or other things that shake the earth.
Mass wasting can be really dangerous because it can damage buildings, roads, and even hurt people. That's why scientists study it to try and figure out when and where it might happen, so we can be safe.