directly to the sea from the Venetian pre-Alps (Adige, Brenta, Piave,
Tagliamento and Isonzo) and the northern Apennines (Reno, Lamone and Marecchia).
The Po-Venetian Plain has a mean altitude of circa 50 m, while in the marginal
belt at the foot of the pre-Alps and the Alps it exceeds 200 m. This is the
point at which it is possible to distinguish a high (gravel and sand) from a low
(mainly mud and clay) plain, separated by a row of springs that have had an
important influence in the development of the plain’s agricultural economy
(cultivation of the rice fields, water etc.). This plain also has an extremely
important economic and social role. Though it forms only a seventh part of the
national territory it contains about a third of the Italian population.
The Apennines
The Apennine range extends for over 1,200 km from the Colle di Cadibona
(touching on the Ligurian Alps) to the extreme south of Calabria and then
includes all the north Sicilian mountains. It forms the mountain backbone of the
Italian peninsula, unfolding in an extensive concave chain that opens towards
the Tyrrhenian Sea. Sometimes its mountains run parallel and sometimes they seem
detached in isolated groups, usually separated by wide valley and basins
(Valdarno, Val Tiberina, Valle del Volturno, Vallo di Diano, Piana del Fucino,
etc.). Furthermore, these alternate with numerous transversal valleys that often
narrow into gorges. As with the Alps so with the Apennines, three sectors can be
distinguished: a northern one of largely sandstones, marls and clays, covering
Liguria, Tuscany and Emilia; a central one essentially of limestones, covering
Umbria-Marches and Latium-Abruzzo; and, finally, a southern one of mixed rock
types, covering Campania, Basilicata and Calabria. Along both edges of the
peninsulaextensive depressions separate the Apennine chains from isolated
reliefs. These are usually given the name Antiapennine: Tuscan Antiapennine,
with the Monti del Chianti, Amiata and Colline Metallifere; Latio-Campania
Antiapennine, with its volcanic belt running from Cimini Mounts to Roccamonfina
and Vesuvio; and Puglia”>Apulian Antiapennine, with the Gargano, Murge and
Salentina Peninsula. In Sicily, the Iblei Mounts can be considered to fulfil an
Antiapennine position. Adjacent to the Antiapennine reliefs and generally
opening on to the sea there are fairly extensive river plains. On the Tyrrhenian
side of the Italian peninsula these consist mainly of the lower Valdarno, the
Ombrone section of the Maremma, the Pontine Marshes and the Campanian plains of
the Garigliano, Volturno and Sele. On the Adriatic side, the largest river
plains are those of the Tavoliere in Puglia and the Piana di Sibari in Calabria.
On the islands there are the plain of Catania in Sicily and that of the
Campidano in Sardinia.
The islands
Besides the reliefs already mentioned, Sicily also has Etna, Italy’s major
active volcano, and a large and undulating inland plateau. The latter is mainly
formed of chalk rocks and rich sulphur deposits that with the heights of the
Monti Erei connect the Iblei to the northern chains (Madonie, Nebrodi, etc.).
Sardinia in its turn is characterized by reliefs of no great height, mainly
formed from crystalline (granites) and volcanic (trachytes and basalts) rocks.
On the western side extend large flat areas like the previously mentioned
Campidano, limited by the gulfs of Cagliari and Oristano. The minor island
groups are mainly present in the Tyrrhenian Sea, such as: the Tuscan archipelago
(290 sq km), dividing the Ligurian and north Tyrrhenian seas; the Campanian
archipelago (71 sq km) with the Pontine Isles; Ustica (8.6 sq km); Aeolian Isles
(115 sq km); Egadi Isles (38 sq km); Pantelleria (83 sq km) and the Pelagian
Isles (25.5 sq km) in the Channel of Sicily. In the Adriatic, besides the
various low and sandy islands of the Po delta and Venetian lagoon, there emerges
the Tremiti archipelago (3 sq km) to the north of the Gargano. Finally, there
are numerous islands along the coasts of Sardinia (Asinara, La Maddalena,
Caprera, San Pietro, Sant’Antioco, etc.,), mainly due to the sinking and
subsequent submersion of the margins of this major Tyrrhenian island.
The coastline
The complexity of the peninsula’s relief is echoed in the diversity of its
coastal profile. Along the low and sandy Adriatic shores this is generally
rectilinear, with the exceptions of the bulge of the Po delta and of the two
rocky promontories of the Conero and Gargano. The Ionian and Tyrrhenian shores
are very different, their extensive sandy curves, corresponding to the edges of
the coastal plains, alternating with high rocky coasts or steep promontories
like those of Piombino, Argentario, Circeo, the Sorrento Peninsula, etc. The
coasts of Sicily and Sardinia present a similar morphological picture, the
latter having frequent rias or deep inlets resulting from the sinking of long
stretches of the eastern coast.
Climatic Conditions
Despite its geographical position at the centre of the temperate zone, Italy has
rather variable climatic characteristics. This is due to the presence of the
Mediterranean, whose warm waters mitigate thermal extremes, and the Alpine arc,
which forms a barrier against the cold north winds. Furthermore, Italy is
subject to both wet and moderate atmospheric currents from the Atlantic Ocean
and dry and cold ones from eastern Europe. The Apennine chain too, confronting
the wet winds from the Tyrrhenian, causes considerable climatic differences
between the opposite sides of the peninsula. The differences in temperature
between the winter and summer months are more marked in the northern regions
than in the south and along the coasts. The mean temperatures for the month of
January in the Po Plain fluctuate around zero, while in the Alpine valleys the
thermometer can drop to -20? and snow can remain on the ground for many weeks.
In the southern regions, instead, the mean temperatures for January remain
around 10?, with the exception of the inland mountainous zones. Mean summer
temperatures throughout all Italy rise to 24?-25? for July, only being lower in
the highest zones. Rainfall distribution also varies considerably, due to the
influence of both mountains and prevailing winds. The highest quantities are
registered in the Alpine arc (over 3,000 mm pa in the Lepontine and Julian Alps)
and on the Apennines (over 3,000 mm pa in the Apuan Alps). The plains, however,
including that of the Po, receive scarce precipitation. Generally it is less
than 800-900 mm pa but in the southern regions (Tavoliere and southern Sicily)
it falls below 600 mm pa. The great internal Alpine valleys and the coastal
plains of the Tyrrhenian (Maremma) and Sardinia also receive little rain.
Altogether, six large climatic regions can be distinguished, mainly
characterized by mountain influence. 1) An Alpine region, strongly influenced by
altitude, with long cold winters and short cool summers having an elevated day-
time temperature range; precipitation is more intense in the summer months,
especially in the pre-Alpine belt. 2) A Po region, with continental conditions,
consisting of cold and often snowy winters and warm and sultry summers;
precipitation is greatest in the spring and autumn months; the climate becomes
milder, however, around the pre-Alpine lakes; fog is frequent, due to the
wetness of the land. 3) An Adriatic region, whose sea has lit tle influence due
to the inability of its shallow waters to trap the summer heat; consequently the
climate has a continental character, with its winters being dominated by cold
north-east winds (bora). 4) An Apennine region, also with continental tendencies
and cold snowy winters; precipitation is more intense on the Tyrrhenian slopes
and is abundant in all seasons apart from the summer. 5) A Ligurian-Tyrrhenian
region, with a maritime climate and heavy and frequent precipitation, which is
less in the summer and distributed irregularly; the winters are cool and the
annual temperature range narrow. 6) A Mediterranean region, also with a limited
annual temperature range; precipitation is frequent, especially in winter, and
the summers are hot and dry. The interior and mountain zones of the islands and
Calabria also have an Apennine type climate due to the altitude.
Inland Waters
The characteristics of the Italian water network are closely associated with
morphological and climatic conditions. There are only a few tens of watercourses
longer than 100 km, though the Po, which is also the longest of them all (652
km) has a rainwater basin almost equal to a fourth of the national territory
(74,970 sq km). Other important rivers are the Adige and Piave, descending from
the Alps and flowing from the north into the Po, and the Arno and Tiber, flowing
through central Italy into the Tyrrhenian. The other main tributaries of the Po
are the Ticino, Adda and Oglio, arising in the Alps, the Tanaro, from the
Apennines, and the Reno too, though it has its mouth to the south of the Po
delta. The rivers running down the Tyrrhenian slopes of the peninsula are
usually longe than those of the Adriatic, because of the Apennine watershed
being further to the east. The Italian waterways are little used for transport
due to their rather limited and variable flow. In fact the Alpine rivers have a
cycle conditioned by the winter snow cover, being high in the summer and low in
the winter; while the pre-Alpine and northern Apennine source rivers are mainly
rain-fed and are only full in spring and autumn. Consequently, the cycle of the
Po River is the most regular and therefore best suited to navigation. The other
rivers of the peninsula and islands are heavily influenced by climatic
conditions, being full in winter and empty in summer. In the latter case it is
not unusual for the bed to remain completely dry, as in the case of the typical
fiumare in Calabria and Sicily. Italy is fairly well supplied with lakes, having
several thousand natural and artificial basins of different sizes and origins.
The largest and deepest occupy the bottom of the great pre-Alpine valleys at
their junction with the Po Plain (from Lake Orta to Lake Garda, which is the
largest of all, while Lake Como is the deepest) and they were all excavated by
Pleistocene glaciers. Also along the Apennine spine there are fairly frequent
large lakes, such as Trasimeno the remains of an older lake that together with
others occupied the bottom of the internal basins of the peninsula. The numerous
small lakes scattered inside the spent craters of Latium and Campania are
volcanic in origin. The coastal plains of the Tyrrhenian, Adriatic and large
islands contain basins that are sometimes extensive and derived from lagoons.
Furthermore, the Italian Alpine slopes, above 2,800 m., contain about a thousand
glaciers. Some of these are of a considerable size, such as the Miage Glacier,
which is some 10 km long and descends the southern slope of Mont Blanc in Valle
d’Aosta. The glaciers are especially important for their function as water
reserves, providing as they do a constant supply for the Alpine rivers. The
central Apennines also have a small glacier, under the northern walls of the
Corno Grande (Gran Sasso). Finally, Italy’s water system is completed by the
many underground water bearing strata of the numerous limestone karst massifs in
the pre-Alps and Apennines. These produce springs bearing a considerable volume
(as that of the Peschiera in Latium or the Sele in Campania, etc.). In addition,
there are those reaching to varying depths under the Po Plain and the other
alluvial plains.
The Italian Seas
With its extension from southern Europe towards Africa, the Italian peninsula
almost divides the Mediterranean in two separate basins. Leaving aside the
Strait of Messina, the shortest distance between Sicily and Africa (NE Tunisia)
is circa 140 km, reduced to 70 km if it is measured from the island of
Pantelleria. In this part of the sea (Channel of Sicily) the depth does not
exceed 500 m. Furthermore, the eastern Mediterranean section, known as the Sea
of Sicily and from which emerge the Maltese Islands, the Pelagian and
Pantelleria, rarely exceeds a depth of 1,500 m. Considerably deeper, on the
other hand, is the Ionian Sea. This extends eastwards from Sicily and Calabria
and southwards from the Salentina Peninsula, touching on the 4,000 m isobath.
Equally deep is the Tyrrhenian Sea, within the triangle formed by Corsica and
Sardinia, Sicily and the Italian peninsula. At its centre it often exceeds a
depth of 3,500 m. A narrow channel (the Canale di Corsica) separates it, to the
north, from the Ligurian Sea. This latter exceeds a depth of 2,000 m in its
western section corresponding to the Riviera di Ponente. The shallowest of the
Italian seas is the Adriatic, which up to the level of Ancona does not exceed 80
m and only at Pescara does it decend below 200 m; off the coast of Puglia,
however, it exceeds a depth of 1,200 m. Finally, in the area of the Strait of
Otranto the two shores of the Adriatic draw close together and here the Italian
and Albanian coasts are only 75 km apart. As for the rest of the Mediterranean,
the surface temperature of the Italian seas is on average rather high. In the
northern Tyrrhenian, the Sea of Sicily, Ionian and southern Adriatic it is circa
13?; in the Ligurian Sea circa 12?; in the southern Tyrrhenian circa 14?; but in
the northern Adriatic, because of the shallowness of the waters, it drops to 9?.
The quality of the water is also rather elevated, re