1 Insertion â when a base is added to the sequence. 2  Deletion â when a base is deleted from the sequence.  Copy number variation (CNV) is a type of mutation where large chunks of DNA are inserted, repeated or lost. These regions of DNA can be between 10,000 and 5,000,000 bases long.
Wind deposition can result in dunes and loess deposits.
The Sahara is mainly rocky hamada (stone plateaus), Ergs (sand seas - large areas covered with sand dunes) form only a minor part, but many of the sand dunes are over 180 metres (590 ft) high. Wind or rare rainfall shape the desert features: sand dunes, dune fields, sand seas, stone plateaus, gravel plains (reg), dry valleys (wadi), dry lakes (oued), and salt flats (shatt or chott).