Rocks slowly break down over time through a set of chemical, physical and biological processes called weathering. Some of these processes are heavily dependent on climate, so certain kinds of rocks weather more rapidly in some climates than in others. The two key climate parameters that affect the rate of weathering are moisture and temperature.
Temperature
Weathering occurs both through physical processes like freezing and thawing and through chemical processes like reactions with carbonic acid that turn silicate minerals into clays. The rate of a chemical reaction increases as the temperature increases, so rocks in warm climates experience faster rates of chemical weathering than rocks in cool climates. Cold climates, by contrast, increase rates of physical weathering, because different minerals expand and contract at different rates when they are heated, so repeatedly heating and cooling the rock eventually causes it to fracture. Desert and mountain climates experience a wide range of temperatures so physical weathering through fracturing accelerates in these environments.
Moisture
Moisture and rainfall are the other critical factor. Some types of rocks weather more rapidly in humid climates, while dry climates make other rocks more susceptible to attack. Limestone, for example, weathers rapidly in wet climates, where rainwater carrying carbonic acid dissolves the limestone to form caves and valleys. Sandstone, by contrast, weathers more rapidly in dry climates, because the quartz in the sandstone is largely invulnerable to chemical weathering, but can fall prey to fracturing caused by ice formed when water freezes and expands in cracks in the stone.
