Chemical change is slowed by cold, dry conditions and mechanical weathering is not so temperature dependent. Thus there is more mechanical weathering than chemical in a cold, dry climate. Mechanical weathering, is the physical breaking up of rocks without any changes in their chemical composition. The roots of trees and shrubs mechanically wedge rocks apart as they grow into cracks, exerting pressure on the walls of the crack and making it larger and larger as the root grows. Carbonation is a reaction between carbonic acid and the minerals making up rocks.
Rainwater is naturally somewhat acidic because it dissolves carbon dioxide from the air.
This forms a weak acid known as carbonic acid, which is the same acid found in your carbonated soda pop. Carbonic acid rain falls on the land, seeping into cracks and crevices where it reacts with minerals. Limestone is easily weathered to a soluble form by carbonic acid and many limestones caves were produced by the chemical weathering of limestone by carbonation. A soil that has balanced amounts of sand, silt, and clay mixed with an abundance of humus is called loam. Loam is a great soil for gardening since it is fertile and well drained, yet holds enough moisture for sustained plant growth.