Dear Serdar,

The first challenge when interpreting a peneplain is recognition of its former full extent, as implied by existing unconformity remnants,— originally eroded together as a coherent plane close to sea level. The second problem is to associate that surface with likely timeframes when it formed, as a whole or in part.

The first problem is confounded by the fact that the original, regionally extensive, flat surface has been faulted, bent, domed and tilted into smooth topographic shapes caused by local Neotectonic isostatic uplift, often of individual mountains. These peneplain remnants often have been overlaid by smoothly conformable detritus left by the original marine/icefloe erosion close to sea level, and dissected by subsequent fluvial, alluvial and landslip events that modified or eroded the original peneplain as it rose, forming youthful valleys in detritus and bedrock.

A good example illustrating these processes will be found in the Grampian Mountains of Scotland, where remnants of the Caledonian Plateau extend between Glen Garry and Nethy Bridge, across complex Dalradian structures and intrusions, without significant regard to variations in rock hardness or minor faults except where nunataks protrude above the original unconformity.

Erosive action by a purely hypothetical thick ice-sheet (ostensibly moving uphill and down dale during the late Devensian) apparently has been negligible.

You pose an excellent question, Serdar. I look forward to other responses.

Malcolm.

One way to look at topographic decay is that there is a lot of material to remove when a mountain range decays. In fluvial conditions, the material leaves the area as sediment in the rivers. The time scale is thus closely related to the rate at which streams and rivers downcut into the bedrock (which depends on steepness, discharge, sediment load, bedrock strength, etc.). You may find some answers in the literature on bedrock channel erosion or on landscape evolution models. People have also studied topographic steady state - the shape of a conceptual mountain range in which the rock is uplifting as fast as it is eroding - and the related literature might be worth having a look at as well.

Thank you very much for your comments, Sir Norman Malcolm Mcclure and Matija Perne. there may be mountain ruins that speed up this process. it is not possible to measure this. everywhere has different dynamics and surface parameters. I think there will be less freezing and thawing at the poles and under the glaciers. therefore, it is difficult to crumble the rocks. a possibility.

I am more likely to think that low embossed erosion surfaces are produced by long-term erosion processes that result in peneplanation of previous reliefs, such as mountain belts, close to sea level. Therefore, low-rise low-rise surfaces on the Earth's surface can be interpreted as a result of a classic surface elevation. Uplift can produce relief rejuvenation to make these surfaces appear as remnants of a dissected peneplain. Could mantle dynamics be required to trigger surface debris?

These fundamentals must be well understood in order to fully understand geomorphology.

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