Weathering is the
breakdown
deposition
formation
transportation

Weathering is the breakdown of rocks by the forces of the atmosphere including due to rainwater and snow melt, heating up as in a desert and freezing and thawing, and oxidation of minerals such as iron-bearing minerals. Altered rocks tend to break down faster than fresh pristine rocks ie rocks subjected to hydrothermal alteration during the formation of some porphyry copper mines can already be clay-rich so if left on, say a mine dump can break down to soil within a few years. Minerals formed at high temperatures deep within the earth when exposed to the much lower temperatures of the atmosphere especially feldspars tend to alter to clay and if this is intense enough the result can be a very crumbly rock well on its way to be a soil,.Alternate freezing and thawing can produce cracking of the rock which allow water to percolate into the rock and combine with the minerals and promote weathering. Also near the surface, iron bearing minerals can oxidize significantly and render the rock softer. 

Answer carbon dioxide ice;