Walker - 1967 - A geography of Italy

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THE N ORTH ERN LOW LANDS
they appear as volcanic rocks and the folds o f upper Tertiary sediments. The
volcanic exposures are best exemplified in the basaltic tuffs and lavas to the west
of Vicenza and between Bassano and Thiene; the Berici and Euganei hills may be
regarded as detached fragments o f this zone although the former also include
Ohgocene clays and the latter are mainly trachytic. From Bassano to beyond
Vittorio Veneto the hill zone is tmderlain by Tertiary sediments folded against
the Pre-Alpine margin; the gentle swelling of Montello immediately to the south
is a low dome o f Miocene limestone.
2 THE APENNiNE H IL L Y M ARGIN. Stretching from Novi Ligure to Pesaro this
zone consists o f a narrow strip o f molasse, repeatedly incised by the rivers and
torrents o f the Apennines and edged with detritus cones. Between the Po and the
Ligurian Apennines the hill country o f the Langhe and Monferrato is developed
on gently folded Tertiary sediments; this area will receive attention below
(p. 128).
3 THE UPPER PL A IN (ALTA p i a n u r a ) . The junction between the moraines and
the fiuvio-glacial deposits o f the upper plain is rarely obvious. The latter is
divided into a succession o f isolated platforms by the incised floodplains o f the
major Alpine rivers; the imperceptible southerly slope o f these platforms is
occasionally interrupted by a shallow step marking the position o f former
shorelines. The surface deposits o f the plain are graded southwards, not always
regularly, from pebbles embedded in gravel to coarse sands. Where the coarser
deposits have been converted into a conglomerate the rivers are sometimes confined
in shallow gorges; at Paderno sull’ Adda one o f these was exploited for
Italy’s first hydro-electric station. Although favourable to easy clearance and
communications, the permeability and altitude o f the fiuvio-glacial platforms
hindered the development o f irrigation; serious progress in this field had to
await the successful diversion o f water from the Alpine rivers on to the interfluves.
Locally the impermeable character o f the surface is interrupted by
ferretto.
4 THE FONTANILI ZONE. Where the coarser deposits o f the aha pianura fall
away to the finer sediments o f the lower plain the alternating exposure o f impermeable
beds and permeable aquifers gives rise to a host o f springs (fontanili).
They are best developed in Lombardy which has over 2000 o f them; they are
less well represented in the upper Po basin (south o f Turin) where the fiuvioglacial
platforms are more fragmentary; in Veneto the zone is interrupted by the
Berici-Euganei hills. Although affected by fluctuations o f the Alpine rivers, the
discharge o f the fontanili is remarkably constant and since the streams to which
they give life are never deeply incised, their waters can be easily distributed.
Even in January they maintain a temperature o f at least io°C , a circumstance
which helps to promote continuous growth in the water-meadows (marche).
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