Peneplain

peneplain

Gently undulating, almost featureless plain near sea level. This would form, theoretically, by various erosional processes that reduce areas of initially high relief produced by active uplift to areas of virtually no relief. The lack of present-day peneplains tends to discredit the theory, but some geomorphologists propose that large areas of low relief at high altitude in some mountains are evidence of uplifted peneplains. Others question whether the dynamic relationship between erosion and rock type would ever allow the development of a peneplain, even over very long timespans.

---

peneplain [′pēn·ə‚plān]

(geology)

base-leveled plain

---

Peneplain 

a denudation plain that has formed where mountainous regions were leveled under humid conditions. In contrast, there are plains whose initially flat relief was the result of accumulation.

The peneplain concept was introduced into geomorphology in the late 19th century by the American geographer W. M. Davis, who considered the peneplain a theoretically conceivable concluding stage of the geographic cycle. According to Davis, the mechanism of peneplain formation consists in the reduction of every point of the surface of a mountainous region by subaerial erosion, but Davis’ explanation is not universally recognized. L. King disagreed with such an explanation of planation and contrasted the concept of the pediplain to that of the peneplain.

Peneplains are formed at the end of major tectonic cycles during the transition from the orogenic stage of development of the earth’s crust to the platform stage. Thick weathering mantles form within peneplains. When tectonic subsidences occur, peneplains may become buried by sedimentary strata; when uplifts occur, peneplains become raised, as in the case of the syrts of the Tien-Shan.

A. E. KRIVOLUTSKII