the chickasaw bluffs are a relatively recent feature. they were formed from pleistocene loess (wind-blown) silt. this loess can be as thick as 70 feet and it generally tapers off as one moves eastward. the loess accumulated on top of fluvial deposits from the pliocene. these primarily consist of terrace gravels deposited from glacial runoff. because of this, the bluffs are slide-prone, especially during seismic activity. the bluffs are characterized by very steep valleys and have higher gradient streams than areas to the east or west. along the western edges facing the river or alluvial plains, the bluffs form nearly vertical cliffs. in memphis, these edges have been smoothed out in the downtown area.