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