Lake Garda ( or ; ; ) is the largest lake in Italy. It is a popular holiday location in northern Italy, between Brescia and Milan to the west, and Verona and Venice to the east. The lake cuts into the edge of the Italian Alps, particularly the Alpine sub-ranges of the Garda Mountains and the Brenta Group. Glaciers formed this alpine region at the end of the last ice age. The lake and its shoreline are divided between the provinces of Brescia (to the south-west), Verona (south-east) and Trentino (north).
Etymology
In Roman times the lake was known as Benacus and by some it was revered as god Benacus, the personification of the lake, sometimes associated with the cult of Neptune. Today it is better known as Lake Garda, a toponym of Germanic origin attested since the Middle Ages and deriving from that of the homonymous town on the Veronese shore of the lake, which, together with another famous locality of the lake, Gardone Riviera, and others less known – such as Gàrdola, Gardoncino, Gardoni, Guàrdola and Le Garde – testifies the Germanic presence in the area that goes from the 6th to the 8th century CE, in particular, the Lombard one. The name Garda is evolved from the Germanic word warda, meaning "place of guard", "place of observation" or "place of safety".
The classic toponym of the lake, or Benācus lacus (Benaco), is almost certainly of Celtic origin, therefore prior to romanization, and should derive from bennacus, comparable with the Irish bennach, which means "horned". The term may derive from the many promontories of the lake.
Geography
Morphology and hydrography
The northern part of the lake is located in a depression that insinuates itself inside the Alps, while the southern part occupies an area of the upper Pianura Padana. The shape is typical of a moraine valley, probably having been formed under the action of a Paleolithic glacier. Although traces of the glacier's actions are evident today, in more recent years it has been hypothesised that the glacier occupied a previously existing depression, created by stream erosion 5 to 6 million years ago.
A characteristic of Garda is the limited size of the hydrographic basin () compared to the lake surface: at a length of of the lake corresponds the of the basin, while the respective widths are 1 and . The eastern watershed of the Benacense basin has a direction parallel to the axis of the lake, while the western one has a more sinuous course. Within the basin, the major peaks are Presanella () and Adamello (). Morphologically, the Garda hydrographic basin can be divided into four areas: the plain of about , the lake surface of about , the western portion of about 500 km² and the eastern one of approximately .
To the south of Lake Garda, between Brescia, Mantua and Verona, a large morainic amphitheatre develops: a succession of hilly circles with small flat areas interposed, in some cases marshy, originated thanks to the transport and storage action of the great Garda glacier. These morainic deposits were formed during the glaciations Günz, Mindel, Riss and Würm: very limited morainic deposits are attributed to the two oldest, Günz and Mindel, while the outer morainic circles are attributed to the Riss glaciation and the inner ones to the Würm glaciation. The morphology of the hills is gentle and with delicate lines; from the highest points, it is possible to perceive the relationships that link the hills to the mountains as well as the circular amphitheatre shape of the hills, which seem to embrace the southern part of the lake.
The main tributary of Lake Garda is the Sarca River, others include the Ponale River (fed by Lago di Ledro), the (via the Cascate del Varone) and various streams from both mountainsides, while the only outlet is the Mincio River (, at Peschiera). The subdivision is created by the presence of a fault submerged between Sirmione and Punta San Vigilio which is almost a natural barrier that hampers the homogenization between the water of the two zones.
If the water level of the Adige river is excessive, water is diverted to the lake through the Mori-Torbole tunnel.
Geology
The Lake Garda area is considered one of the most seismic in Italy. The oldest known earthquake that struck the Garda region seems to have occurred in 243 (or perhaps 245): it was so disastrous that the city of Benaco, located where Toscolano Maderno stands today, suddenly disappeared. The disappearance of the town is probably due to the cracking and landslide of the mountain above Toscolano, which caused the flooding of a small lake enclosed by the mountains, whose waters submerged the populous town.