Environmental Engineering Reference
In-Depth Information
4.4.4 Landscapes of effusive rocks
These landscapes are characterized by different rock types, with different forms
and degrees of acidity. The landscapes are thus characterized by lava flows of basalt
and acid forms with steep slopes on the more acid rocks and more or less harsh
forms for the andesites. On flat surfaces of the highlands with basic rocks, soils
belong mainly to the Lithic Xerorthents and to the Typic and Lithic Xerochrepts,
alternated with long stretches of rock outcropping. Since these are soils with high
fertility, they have always been used for grazing and partly for agriculture. This
explains the presence of large areas with very thin soils and rocky outcrops, which
are the result of widespread erosion. The soils on basalt or tuff on higher elevations
may show andic characteristics due to the presence of amorphous materials (high
water retention capacity, low density, high cation-exchange capacity and retention
capacity for phosphorus, etc.). The landscape on andesites is characterized by a
predominance of rocky outcrops, while at the base of mountains it is not uncommon
to find Vertisols supporting an intensive agriculture. The ignimbrites have mixed
forms: rough areas and sub-flat. In any case, rarely will you encounter evolved soils,
but only forms of degradation. The natural vegetation, where it exists, generally
comprises cork oak forests and more or less evolved scrub. These landscapes are
mainly present in the mountains of southern Italy, where volcanism is active.
4.4.5 Landscapes on marly, arenaceous and calcareous-marly rocks
The landscape which has evolved over these rocks presents undulating characters
in the marly-arenaceous formations and rugged forms on limestone formations. Se-
quences of soils are typical on the basis of morphology (chains) with Entisols at
the top of the hills, Inceptisols on slopes and Vertisols in lowland areas. On the
arenaceous rocks the chains are composed of Lithic Xerorthents at the top of the
mountains, Calcic Xerochrepts on the slopes and Typic Xerochrepts at the base.
Erosion is very active even though these substrates (mostly marls and sandstones)
allow a quick change with the formation of soils in a relatively short time. Typi-
cal examples of these landscapes are found in the Italian Apennines where extreme
erosional features such as badlands are present (e.g. 'Calanchi' and 'Bianchane').
4.4.6 Landscapes on detritus and debris cones
The quality of the soil depends on the lithological characteristics of the materials
from which it originated - detritus, morphometric characteristics and vegetation.
The soil has a rocky or stony surface. It may appear excessively drained and typi-
cally has a medium texture. The organic matter content in surface horizons is very
