What Is a Thick Weathering Zone?

Process

• Weathering can start via earthquakes, gravity and rockslides. Areas that contain water can speed the fracturing of rock, allowing microbes to penetrate the surfaces of rocks and consume the inorganic materials inside. These microbes are then consumed by other organisms, or die and form a layer of nutrients that plants can exploit. As rock breaks down into even smaller fragments, it eventually turns into a layer of soil. The process creates a self-reinforcing cycle that allows the support of more life until organisms have utilized all available resources in the critical zone.

Types

• The rate of erosion determines whether an area features a thin or thick weathering zone. If an area experiences erosion faster than natural processes can completely break down rock deposits, scientists classify it as a thin weathering zone. A thick weathering zone experiences erosion at a slower rate than processes that break down rock deposits. The availability of nutrients can equal the rate of erosion, or the thick weathering zone can become thicker if the process allows nutrients to accumulate faster than erosion.

Benefits

• Support for all life comes from inorganic matter. Broken down rocks contain materials essential for microbial, plant, and animal life, including calcium, potassium, magnesium, and phosphorus. Thick weathering zones feature abundant nutrients, causing plants to colonize the zone and form a layer of thick soil. Plant roots hold in organic material, further thickening the weathering zone by allowing microorganisms to completely break down rocks.

Geography

• Thick weathering zones typically develop in areas of lower elevation that are in close geographical proximity to areas of higher elevation. Mountains often have a thin weathering zone, because rocks that break off the mountain roll down the mountainside and fracture. These rocks become trapped in valleys, where they are broken down completely and form a thick weathering zone.