Why Italy is a boot
The boot is a mountain range. The Apennines, a young chain pushed up where Africa and Europe collide, run the length of the peninsula, and the sea opening up behind them shaped its western coast. Italy’s borders follow the peninsula and the Alps above it, a line the country only reached after 1919.
Written from cited sourcesLast checked 30 September 2026Suggest a correction
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A mountain range in the sea
Italy is often described as shaped like a boot. The Alps stand across its broad top, and the Apennine Range runs down its whole length.[1] The Apennines form a great arc of about 1,400 km, from the Cadibona Pass near the Maritime Alps down the peninsula to Calabria, where they turn south and then west into Sicily.[2]
The mountains are the peninsula. The Apennines are 32 km wide at either end and about 190 km wide east of Rome, and plains, mostly the Po valley in the north, cover less than a quarter of the country.[3] The boot’s “heel”, in Puglia, is a low limestone plateau that the mountain-building barely touched.[2]
Squeezed between Africa and Europe
The rocks of the Apennines are mostly shales, sandstones and limestones laid down on the floor of the Tethys, an ocean that lay between the African and European plates more than 65 million years ago. The chain was then folded and pushed up, mainly between about 23 and 2.6 million years ago, making it one of the younger ranges of the Alpine system.[2]
About 10 million years ago the crust on the western side began to thin and pull apart, opening a new sea, the Tyrrhenian, between the peninsula and the islands.[2] Sardinia and Corsica are older rocks that broke away from the coast of Spain and France about 20 million years ago.[2] The same faults feed volcanoes: Vesuvius, the Aeolian Islands and Etna are still active, and earthquakes are common along the whole chain, driven by the plates’ complicated collision.[2]
Borders to match
For centuries the peninsula was split between several states. Piedmont, with French help, defeated Austria in 1859 and united most of Italy by 1861; Venetia followed in 1866 and papal Rome in 1870.[4]
The northern border reached the crest of the Alps only after the First World War. In the Treaty of Saint-Germain, signed on 10 September 1919, Austria gave up Trento, southern Tyrol, Trieste and Istria, and Austrians protested that many German speakers were placed under Italian rule.[5] Today the Alps separate Italy from France, Switzerland, Austria and Slovenia, and the sea surrounds the rest.[3]
Timeline
c. 23–2.6 million years ago
The Apennines rise
The main phase of mountain-building.[2]
c. 20 million years ago
Corsica and Sardinia part
The islands break away from the Spanish and French coast.[2]
c. 10 million years ago
Tyrrhenian Sea opens
The crust west of the peninsula starts to thin and pull apart.[2]
1861
Kingdom of Italy
Piedmont unites most of the peninsula.[4]
1870
Rome
Papal Rome is annexed, completing unification.[4]
191910 September 1919
Treaty of Saint-Germain
Austria gives up Trento, southern Tyrol, Trieste and Istria.[5]
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Sources
- [1]Italy · Encyclopaedia Britannica
- [2]Apennine Range · Encyclopaedia Britannica
- [3]Italy: Land · Encyclopaedia Britannica
- [4]Risorgimento · Encyclopaedia Britannica
- [5]Treaty of Saint-Germain · Encyclopaedia Britannica
Map geometry from Natural Earth via world-atlas. See credits.