Map of Switzerland

Geography

According to the Swiss Federal Office of Topography, Swisstopo, Lac de Genève designates that part of the Petit Lac which lies within the cantonal borders of Geneva (excluding the cantonal exclave Céligny), so about from Versoix–Hermance to the Rhône outflow in Geneva.

The Chablais Alps border is its southern shore, and the western Bernese Alps lie over its eastern side. The high summits of Grand Combin and Mont Blanc are visible from some places.

The lake lies on the course of the Rhône. The river has its source at the Rhône Glacier near the Grimsel Pass to the east of the lake and flows down through the canton of Valais, entering the lake between Villeneuve and Le Bouveret, before flowing slowly towards its egress at Geneva.

Climate

Due to climate change, the average temperature of deep water (more than 300 metres or 980 feet deep) increased from 4.4 °C (39.9 °F) in 1963 to 5.5 °C (41.9 °F) in 2016, while the average temperature of surface water (five metres or 16 feet deep) increased from 10.9 °C (51.6 °F) in 1970 to 12.9 °C (55.2 °F) in 2016 (up 2 °C or 3.6 °F in 46 years).

Lake Geneva (and particularly the lakeside parts of the city of Geneva) can be affected by the cold bise, a northeasterly wind. This can lead to severe icing in winter. The strength of the bise wind can be determined by the difference in air pressure between Geneva and Güttingen in canton of Thurgau. The bise arises when the air pressure in Güttingen is higher than in Geneva.

Geography

Lake Constance is located in the foothills of the Alps. The shore length of both main lakes is 273 kilometres (170 mi) long. Of this, 173 kilometres (107 mi) are located in Germany (Baden-Württemberg 155 kilometres or 96 miles, Bavaria 18 kilometres or 11 miles), 28 kilometres (17 mi) run through Austria and 72 kilometres (45 mi) through Switzerland. If the upper and lower lakes are combined, Lake Constance has a total area of 536 km2 (207 sq mi), the third largest lake in Central Europe by area after Lake Balaton (594 km2 or 229 sq mi) and Lake Geneva (580 km2 or 220 sq mi).

History

Lake Constance was formed by the Rhine Glacier during the Quaternary glaciation ice age and is a Zungenbecken or Tongue lake. After the end of the last glacial period, about 10,000 years ago, the Obersee and Untersee still formed a single lake. The downward erosion of the High Rhine caused the lake level to gradually sink and a sill, the Konstanzer Schwelle, to emerge.

The Rhine, the Bregenzer Ach, and the Dornbirner Ach carry sediments from the Alps to the lake, thus gradually decreasing the depth and reducing the extension of the lake in the southeast.

In antiquity, the two lakes had different names; later, for reasons which are unknown, they came to have the same name.

In the 19th century, there were five different local time zones around Lake Constance.

Ecology

Until the 19th century, Lake Constance was a natural lake. Since then, nature has been heavily influenced by clearing and the cultivation of much of the land around its shores. However, some near-natural areas have been largely conserved, especially in the nature reserves, or were re-naturalised. As a result, the Lake Constance region has some unusual ecological features. These include the large forested area on the Bodanrück, the occurrence of marsh gentian and orchids of the genera Dactylorhiza and Orchis in the Wollmatinger Ried, and the Siberian iris (Iris sibirica) in the Eriskircher Ried, which was therefore given its own name.

Description

Lake Constance is located along the Rhine between the Alpine Rhine, its main tributary, and the High Rhine, its outflow. It is the third largest freshwater lake by surface area in Central and Western Europe (and the second largest in volume), after Lake Geneva and (in surface area) Lake Balaton.

It is 63 km (39 mi) long, and, nearly 14 km (8.7 mi) at its widest point. It covers about 536 km2 (207 sq mi), and is 395 m (1,296 ft) above sea level. Its greatest depth is 252 metres (827 ft), exactly in the middle of the Upper Lake. Its volume is about 48 km3 (12 cu mi).

The lake has two parts.

Geography and geology

Lake Como is situated in the Lombardy region of Northern Italy, at the southern end of the Alps, about 45 km north of Milan. Geologically, it lies within the Southern Alps, specifically the Lombardic Basin, an area shaped by a complex history of tectonic activity and surface processes. The region experienced significant rifting during the Mesozoic Era followed by compressional forces during the Alpine orogeny in the Cenozoic Era, related to the collision of the African and Eurasian plates. This compression phase, particularly activity along major fault systems near the Periadriatic Seam (like the Insubric Line), influenced the landscape's structure.

History

The area around Lake Como has been inhabited since prehistoric times, although the first significant settlement, Comum, emerged during the Iron Age (first millennium BC), embedded within the broader Golasecca culture. Its strategic position between the northern regions and the Po Valley made it important early on. In 196 BC, the Roman army under Consul Claudius Marcellus conquered the area from the Celtic Comenses. The settlement was fortified after raids by Rhaetian tribes. Under Roman rule, the area became a key strategic outpost. The Romans constructed the Via Regina, a vital road connecting the lake (Larius, as they called it) with the Rhaetian region to the north and serving as an important trade route between the Po Valley and the Rhine Valley under Emperor Augustus.

Ecology

The mild, humid climate influenced by the lake supports a rich diversity of plant life characteristic of the Insubria region. Along the immediate shores and lower slopes, Mediterranean species like olive trees (historically cultivated, evidenced by names like Oliveto Lario), laurel, myrtle, and cypress thrive. The villa gardens famously cultivate exotic subtropical plants alongside native species. Vegetation is strongly zoned by altitude: foothills (up to 800 m) are dominated by mixed deciduous forests of oak (including downy oak on drier slopes), chestnut, hornbeam, manna ash, and poplar. Higher elevations transition to beech forests and then extensive conifer forests (including silver fir, spruce, larch, and mountain pine).

Climate

According to the Köppen climate classification, Lake Como experiences a humid subtropical climate. The average temperature in the surrounding region fluctuates from 4 °C (39 °F) in January to 25 °C (77 °F) in July. The water temperature reaches an average of 26 °C (79 °F) in July, making it pleasant for water activities during the summer months.

The climate around Lake Como features distinct seasonal variations. During winter, the lake exerts a moderating influence, helping to maintain a mild average temperature of 7 °C (45 °F) in the nearby area.

Geography

The Alps are a crescent shaped geographic feature of central Europe that ranges in an 800 km (500 mi) arc (curved line) from east to west and is 200 km (120 mi) in width. The mean height of the mountain peaks is 2.5 km (1.6 mi). The range stretches from the Mediterranean Sea north above the Po basin, extending through France from Grenoble, and stretching eastward through mid and southern Switzerland. The range continues onward toward Vienna, Austria, and southeast to the Adriatic Sea and Slovenia. Depending on the definitions used, the Alpokalja foothills in western Hungary may also qualify as part of the Alps.

To the south it dips into northern Italy and to the north extends to the southern border of Bavaria in Germany.

Geology

Important geological concepts were established as naturalists began studying the rock formations of the Alps in the 18th century. In the mid-19th century, the now-defunct idea of geosynclines was used to explain the presence of "folded" mountain chains. This theory was replaced in the mid-20th century by the theory of plate tectonics.

The formation of the Alps (the Alpine orogeny) was an episodic process that began about 300 million years ago. In the Paleozoic Era the Pangaean supercontinent consisted of a single tectonic plate; it broke into separate plates during the Mesozoic Era and the Tethys sea developed between Laurasia and Gondwana during the Jurassic Period.

Ecology

Thirteen thousand species of plants have been identified in the Alpine regions. Alpine plants are grouped by habitat and soil type which can be limestone or non-calcareous. The habitats range from meadows, bogs, and woodland (deciduous and coniferous) areas to soil-less scree and moraines, and rock faces and ridges. A natural vegetation limit with altitude is given by the presence of the chief deciduous trees—oak, beech, ash and sycamore maple. These do not reach the same elevation, nor are they often found growing together, but their upper limit corresponds accurately enough to the change from a temperate to a colder climate that is further proved by a change in the presence of wild herbaceous vegetation.

History

When the ice melted after the Würm glaciation, Paleolithic settlements were established along the lake shores and in cave systems. Evidence of human habitation has been found in caves near the Vercors Cave System, close to Grenoble and Echirolles. In Austria, the Mondsee lake shows evidence of houses built on piles. Standing stones have been found in the Alpine areas of France and Italy. About 200,000 drawings and etchings have been documented, and are known as the Rock Drawings in Valcamonica.

A mummy of a Neolithic human, known as Ötzi, was discovered on the Similaun.

Ecology

Some alpine butterfly populations have reduced markedly recently. Butterflies have been shown to be more vulnerable to climate change than birds. A study of three such alpine butterfly species over a period of the last glacial cycle suggests habitat loss and its deterioration are major drivers of this decline in population.

Tourism

The Jura range offer a variety of tourist activities including hiking, cycling, downhill skiing and cross-country skiing. There are many signposted trails including the Jura ridgeway, a 310 km (190 mi) hiking route. Several peaks feature observation towers (e.g. Faux d'Enson, Hage).

Tourist attractions in the Swiss Jura include natural features such as the Creux du Van, lookout peaks such as the Chasseral, caves such as the Grottes de Vallorbe, as well as gorges such as Taubenloch. The Swiss Jura has been industrialized since the 18th century and became a major centre of the watchmaking industry.