செம்மண் என்ற மண்வகை, செவ்வாய் கோளிலும் இருப்பதாக விண்வெளி ஆராய்ச்சிகள் புலப்படுத்துகின்றன. நாம் வாழும் பூமியின் மண்ணைப் பொதுவாக நான்கு வகைகளாகப் பிரிக்கலாம். அவை,

1. செம்மண்
2. செம்புறை மண்
3. கரிசல் மண்
4. வண்டல் மண் என்பனவாகும்.

Ultisol, commonly known as red clay soil, is one of twelve soil orders in the United States Department of Agriculture soil taxonomy. The word "Ultisol" is derived from "ultimate", because Ultisols were seen as the ultimate product of continuous weathering of minerals in a humid, temperate climate without new soil formation via glaciation. They are defined as mineral soils which contain no calcareous material anywhere within the soil, have less than 10% weatherable minerals in the extreme top layer of soil, and have less than 35% base saturation throughout the soil. Ultisols occur in humid temperate or tropical regions. While the term is usually applied to the red clay soils of the Southern United States, Ultisols are also found in regions of Africa, Asia, Australia and South America.