Page 171 - Fundamentals of Geomorphology

154 PROCESS AND FORM

Weathering is the breakdown of rocks by mechanical WEATHERING PRODUCTS AND
disintegration and chemical decomposition. Many rocks LANDFORMS
form under high temperatures and pressures deep in the
Earth’s crust. When exposed to the lower temperatures Weathering waste
and pressures at the Earth’s surface and brought into con- Regolith
tact with air, water, and organisms, they start to decay.
The process tends to be self-reinforcing: weathering The weathered mantle or regolith is all the weathered
weakens the rocks and makes them more permeable, so material lying above the unaltered or fresh bedrock
rendering them more vulnerable to removal by agents of (see Ehlen 2005). It may include lumps of fresh bedrock.
erosion, and the removal of weathered products exposes Often the weathered mantle or crust is differentiated
more rock to weathering. Living things have an influ- into visible horizons and is called a weathering pro-
ential role in weathering, attacking rocks and minerals file (Figure 6.1). The weathering front is the boundary
through various biophysical and biochemical processes, between fresh and weathered rock. The layer immedi-
most of which are not well understood. ately above the weathering front is sometimes called

Stone
line

Mobile
zone
Quartz
vein

Regolith
Saprolite
Rounded
corestone
Grus
Angular
corestone Saprock
Weathering
front

Fresh
bedrock
Granite

Figure 6.1 Typical weathering profile in granite. The weathering front separates fresh bedrock from the regolith.
The regolith is divided into saprock, saprolite, and a mobile zone.