Frost Wedging hiya kids!=)
Sedimentary rocks can be both chemically and mechanically weathered.
The rate of chemical weathering increases when a rock becomes more mechanically weathered, also called abrasion.
Mechanically
The layer of soil that contains weathered rocks is the subsoil. This layer is located beneath the topsoil and consists of partially weathered rocks and minerals.
Weathered rocks that are composed of smaller fragments and grains are referred to as sedimentary rocks. These rocks are formed through the process of erosion, transportation, deposition, and lithification of the weathered materials.
Sedimentary rocks made of weathered rock fragments are called clastic sedimentary rocks. These rocks are formed from the accumulation and cementation of fragments that have been weathered, eroded, and transported from their original source. Examples include sandstone, shale, and conglomerate.
Mechanical weathering breaks down rocks into smaller fragments without altering their chemical composition, resulting in pieces that retain the original mineralogy. In contrast, chemical weathering involves chemical reactions that change the minerals within the rock, producing new minerals and soluble ions. Consequently, the mechanically weathered rock would consist of unchanged mineral fragments, while the chemically weathered rock would yield altered materials, such as clay minerals or dissolved substances. This difference affects the soil composition and ecosystem dynamics in the surrounding area.
Some weathered rocks have rust streaks due to the iron content in the rocks. When rocks that have ferrous iron are weathered there will be rust streaks present.
Neither, at the surface all rocks become weathered.
NO
Soil is a mixture of organic matter and weathered rocks. Organic matter comes from decomposed plant and animal material, while weathered rocks contribute minerals and nutrients to the soil.
Sandstone.