* Increased surface area. When a rock is mechanically weathered, it is broken down into smaller pieces. This increases the surface area of the rock that is exposed to the elements. The more surface area that is exposed, the more water, oxygen, and other weathering agents can come into contact with the rock and cause chemical reactions to occur.
* Stresses. Rocks that are broken into smaller pieces are also more fractured and cracked. These fractures and cracks provide pathways for water and other weathering agents to penetrate the interior of the rock and further break down its chemical composition.
* Mineral surfaces. The surfaces of freshly fractured rocks are more reactive than the surfaces of older, weathered rocks. This is because the freshly fractured surfaces contain more exposed mineral grains that are susceptible to chemical reactions.
* Higher temperatures. The temperature inside rocks that are mechanically weathered is often higher than the temperature of the surrounding environment. This is because the process of mechanical weathering generates heat. Higher temperatures can accelerate chemical reactions, which can lead to more rapid chemical weathering.
As a result of these factors, rocks that are mechanically weathered are more likely to undergo chemical weathering than rocks that are not weathered. This is why it is common to find areas with a high degree of mechanical weathering also having a high degree of chemical weathering.
