A 1994 review argues that only the concepts of desert, glacial, periglacial and a few coastal morphoclimatic zones are justified. These zones amounts to about half of Earth's land surface, the remaining half cannot be explained in simple terms by climate-landform interactions. The limitations of morphoclimatic zoning were already discussed by Siegfried Passarge in 1926 who considered vegetation and the extent of weathered material as having more direct impact than climate in many parts of the World. According to M.A. Summerfield large-scale zoning of the relief of Earth's surface is better explained on the basis of plate tectonics than on climate. An example of this are the Scandinavian Mountains whose plateau areas and valleys relate to the history of uplift and not to climate.