Earth is a big object made of many different types of rocks and minerals. At any given moment, there is someplace where it is sunny, rainy, windy, humid, dry, hot, or cold. There is a place where someone is walking, a river is running, an animal is digging, plant roots are growing, and water is dripping, freezing, or thawing. Environmental conditions constantly bombard rocks at different intensities, affecting the rates at which they weather.

Most weathering does not happen overnight. It is a gradual process that occurs over hundreds, thousands, and even millions of years.

Type of Rock

Each type of rock has a unique set of physical properties. These physical properties affect the way it reacts to certain conditions and ultimately affects the rate at which it weathers.

The type of rock and the environmental conditions to which it is exposed are two of the main factors that affect how fast weathering occurs on a specific rock. In an environment bombarded by the abrasive forces of wind, water, and ice, a harder rock, like granite, will weather more slowly than a softer rock, like sandstone. If acid rain is present, limestone will wear away a lot faster than other rocks due to the calcite in the limestone.

Surface Area

Surface area is the measure of area on the outside of an object, such as a rock. The surface area of a rock can affect the rate at which it weathers. Generally, the greater the surface area of a rock, the faster it will weather. As a rock weathers, it may begin to form cracks. Over time, continual weathering will increase the size of these cracks, which in turn, will increase a rock’s surface area as more area is now exposed to the outside. This process can compound over time and can eventually lead to the breakdown of the rock.

Exposure

Uncovered rocks are exposed to elements, such as wind, rain, sunlight, freezing, and thawing. These rocks will generally weather much faster than those covered by soil, water, or ice. For example, a large boulder that is mostly buried may not weather as quickly as a smaller rock that is lying on top of the ground.

Climate

Climate is the combination of temperature, humidity, rainfall, and sunlight at a given region on Earth. Different combinations of these factors affect the rate at which rocks weather.

Hot and humid conditions accelerate the oxidation process of rocks containing iron. Large fluctuations in daily temperatures can result in the continual expansion and contraction of rocks. These areas will exfoliate rocks faster than areas where temperatures are more constant.

Regions of heavy rainfall will weather sedimentary rock, such as sandstone, much faster than dry climates. Weathering rates also increase in regions of the world that experience acid rain.

Human Activity

Human activities can be the biggest influence on weathering rates. For example, clearing land for the construction of roads and building projects using bull dozers and dynamite may accelerate weathering. What may have taken millions of years to naturally break down, happens in a matter of days or weeks due to human activity.

Landscaping and agricultural practices can unearth rocks that were once protected by layers of soil. Mining breaks down rocks deep within Earth and brings them up to the surface. Clear cutting of forests can also influence the way rocks are exposed to the different elements of nature. Trees that once shielded rocks and minerals from weathering are removed, leaving the rocks and minerals exposed. These activities all work to accelerate the exposure of rocks to natural elements, like wind, rain, sunlight, temperature, and acids. Increased exposure to the elements ultimately leads to increased weathering rates.

Industrialization also affects weathering rates. As our need for energy increases, so does the carbon dioxide released into the atmosphere. This greenhouse gas contributes to the formation of acid rain, which can cause weathering.