Errosion is an ongoing process. While any land is elevated higher than sea level it occures all the time. For this reason you question can not be answered.
on rocky mountains
on rocky mountains
Weathering and erosion occur all the time even when mountains are forming
avalanch
erosion occur outside because water and wind cause erosion
Most of the world's tornadoes happen in an area called "Tornado Alley". It is between the Rocky Mountains and Appalachian Mountains. It's a huge area.
Mountains occur on all continents and can be found at different elevations and in various geological settings. They form through tectonic processes like plate collisions, volcanic activity, and erosion. Some famous mountain ranges include the Andes in South America, the Himalayas in Asia, and the Rocky Mountains in North America.
Water erosion occurs wherever there is water: high in the mountains, or on the coast. It occurs mostly by rivers and on beaches, but occurs on a smaller scale with gulley erosion and others caused by rainfall.
Theoretically tornadoes can occur anywhere on earth, but they are most common in North America between the Rocky Mountains and Appalachian Mountains. There is a place in the US called Tornado Alley
water erosion
Tornadoes occur there because warm moist air from the Gulf of Mexico meets cool dry air from the Rocky Mountains or Canada, this creates the thunderstorms that can spawn tornadoes.
soil erosion mostly occur in hilly areas,coastal areas etc.