Mechanical or physical weathering involves the breakdown of rocks and soils through direct contact with atmospheric conditions, such as heat, water, ice and pressure. Chemical weathering, involves the direct effect of atmospheric chemicals or biologically produced chemicals (also known as biological weathering) in the breakdown of rocks, soils and minerals. These types of weathering are similar in the sense that they both are types of erosion, and work together in eroding rocks, soils, and minerals. In contrast, they are different because of how they occur. Chemical weathering could be stopped, because it is a result of chemicals in the atmosphere. However, mechanical weathering is a natural process that erodes through weather.