Question

How are plains formed

Answer 1

I say The answer is vlocano erupts

[hope this helps]

Answer 2

1) Plains are formed when everything in the land weathered or eroded away,leaving the land flat.
and
2) Another way is when volcano erupt ,and burn everything in its way,all that is left are the plains,This makes bare land or barren plains.
The most common are from dried up lakes or a glacier moving past an area.