The usual agents of mechanical weathering are pressure, temperature, freezing/thawing cycle of water, plant or animal activity, and salt evaporation. When water evaporates, salts precipitate. If this happens in fractures in rock, the growth of the salt crystals can put pressure on the cracks, causing them to grow. This process is most important near oceans where rocks are exposed to lots of salt water spray and in arid environments where water evaporates rapidly. Moisture speeds up chemical weathering. Weathering occurs fastest in hot, wet climates. It occurs very slowly in hot and dry climates. Without temperature changes, ice wedging cannot occur. Temperature changes can also contribute to mechanical weathering in a process called thermal stress. Changes in temperature cause rock to expand (with heat) and contract. As this happens over and over again, the structure of the rock weakens. Over time, it crumbles. During evaporation, the molecules of the liquid that are present at its surface overcome the intermolecular forces of attraction to break away from the liquid and escape into the atmosphere as a gas. The more water present, the faster weathering occurs. Temperature is also important. Warmer temperatures promote faster reactions, so chemical weathering is more effective in warm climates. Thus, warm, humid climates tend to have the most rapid weathering. Mechanical weathering is also physical weathering and dis aggregation, causes rocks to crumble. Water, in either liquid or solid form, is often a key agent of mechanical weathering. For instance, liquid water can seep into cracks and crevices in rock. Chemical weathering is the process by which rocks are broken down by chemical reactions. There are different types of chemical weathering. Hydrolysis is the chemical breakdown of a substance when combined with water. The most common example of hydrolysis is feldspar in granite rocks changing to clay. Physical weathering involves the breakdown of rocks and soils through the mechanical effects of heat, water, ice, or other agents. Chemical weathering involves the chemical reaction of water, atmospheric gases, and biologically produced chemicals with rocks and soils. Chemical weathering occurs when water gets inside of a rock and reacts with some of the mineral components of the rock, chemically changing them and weakening the rock's structure. This causes the rock as a whole to break down, and over time chemical weathering can break a rock into small enough pieces to become soil.

Mechanical weathering, also called physical weathering and disaggregation, causes rocks to crumble. Water, in either liquid or solid form, is often a key agent of mechanical weathering. For instance, liquid water can seep into cracks and crevices in rock. Chemical weathering is the process by which rocks are broken down by chemical reactions. There are different types of chemical weathering. Hydrolysis is the chemical breakdown of a substance when combined with water. The most common example of hydrolysis is feldspar in granite rocks changing to clay. Chemical weathering involves the interaction of rock with mineral solutions to change the composition of rocks. In this process, water interacts with minerals to create various chemical reactions and transform the rocks. When rocks are exposed to wind, rain, heat and frost, they break apart and crumble to form fine particles over a period of time. This process of mechanical and chemical break down of rocks is as weathering. Chemical weathering occurs when water gets inside of a rock and reacts with some of the mineral components of the rock, chemically changing them and weakening the rock's structure. This causes the rock as a whole to break down, and over time chemical weathering can break a rock into small enough pieces to become soil. When water evaporates, salts precipitate. If this happens in fractures in rock, the growth of the salt crystals can put pressure on the cracks, causing them to grow. This process is most important near oceans where rocks are exposed to lots of salt water spray and in arid environments where water evaporates rapidly. The usual agents of mechanical weathering are pressure, temperature, freezing/thawing cycle of water, plant or animal activity, and salt evaporation. Temperature changes can also contribute to mechanical weathering in a process called thermal stress. Changes in temperature cause rock to expand and contract. As this happens over and over again, the structure of the rock weakens. Over time, it crumbles. Water can get into cracks in a rock and, if it freezes, the ice will expand and push the cracks apart. When the ice melts, more water can get into the larger crack; if it freezes again it expands and can make the crack even bigger.