Cliff+erosion+page

====The **cliff erosion cycle** hypothesis suggests that cliff erosion occurs in cycles. The cycle is demonstrated below. Since phase 1 makes an ideal habitat for the Puritan tiger beetle, local populations reach their maximum at this time, and decrease through phases 2, 3, and 4 (24).====

====Building revetments (retaining walls) at the base of these cliffs stops this natural cycle, and has negative consequences for the suitability of the habitat for the Puritan tiger beetle. Immediately following wall construction, vegetation fills in behind the wall, colonizing the loose sediment at the base of the cliff (**colluvium**), similar to phase 3. However, the cycle does not continue to phase 4, and then back to phase 1 since erosion occurs much more slowly with the walls in place. Because of this human intervention, Puritan tiger beetle populations never rebound. Instead, they will abandon the site, leading to local extinctions where populations had existed previously (24).====

====One important aspect of cliff erosion is that it does not occur at the same rate in all the cliffs along the Chesapeake bay. Geologists have determined that are several factors that determine how a cliff will erode. To examine these factors, click here. As you can see, erosion is an inevitable process - attempts to intervene will change the pattern but not stop it. Local geology and erosive forces - not engineering - ultimately determine how fast a cliff top retreats (35).====