Complex sentence: Sikeston Ridge is a about a 20 foot high and two mile wide topographic terrace deposited by the Ohio River which was formed many years ago when the Mississippi River flowed west of Sikeston.
Split into simpler sentences: Sikeston Ridge is a two mile wide topographic terrace with an average height of 20 feet deposited by the Ohio River. It was formed many years ago when the Mississippi River flowed west of Sikeston.