Denudation, weathering and mass wasting - Fundamentals of the Physical Environment - page 296

Description Class Profile Porosity

(%)

Compressive
Strength

Deformability

SOIL: Complete destruction
of original texture,
structure and mineralogy.

VI

60

COMPLETELY WEATHERED:
Decomposed, friable;
some evidence of rock
texture and structure.

20

V

6.0

HIGHLY WEATHERED:
Weathering throughout
zone; material partly friable.

IV

2.0

MODERATELY WEATHERED:
Weathering throughout
zone but no friability.

III

0.6

SLIGHTLY WEATHERED:
Weathered discontinuity
surfaces; slight weathering
further into mass.

II

0.2

INTACT ROCK: Fresh rock -
no sign of weathering, or
limited to discontinuity
surfaces.

I

500 LOW-HIGH

0.05 5

MN m -2

Figure 13.10 Weathering profile and some geotechnical properties.
Source: Partly after Dearman (1974)

Plate 13.8 A granite inselberg in the Joshua Tree National
Park, southern California. Severe chemical weathering along
joints has reduced many blocks to huge residual boulders,
indicating that contemporary desert climate has replaced earlier
more humid conditions, maybe through recent tectonic uplift.
Photo: Ken Addison

Plate 13.9 Later Cenozoic deep subtropical chemical
weathering of Atlantic sea-floor spreading basalts, now
onshore, exhumed by cool-climate conditions on the Antrim
coast, Ulster.
Photo: Ken Addison