The Tagus Estuary

Where it is

The Tagus is Iberia's longest river, and at Lisbon it opens into a broad shallow basin the Portuguese call the Mar da Palha, the Sea of Straw, before narrowing again into a deep channel to the Atlantic. That shape is the point: a large sheltered anchorage, entered through a defensible mouth, sitting almost on the open ocean rather than up a long approach. Lisbon is on the north bank where the hills come down to the water, which is why it is a city of viewpoints and funiculars.

The land and water around it

• The Mar da Palhagulf

  The wide shallow basin upstream of the narrows, with extensive mudflats. It is a major wintering ground for waders and flamingos, and it is why the harbour is sheltered.

• The narrowsstrait

  The deep channel between Lisbon and Almada. Defensible, navigable by large ships, and now crossed by the 25 de Abril bridge.

• The Lower Tagus valley faultbasin

  The valley sits on an active fault system, and the region is exposed both to local earthquakes and to those offshore in the Atlantic. 1755 came from the sea.

Its history, in short

Phoenicians, Romans and Muslims each used the harbour; the Roman name Olisipo and the Arabic al-Ushbuna both survive in Lisboa. Portuguese forces took the city in 1147, and from the fifteenth century the estuary became the departure and return point for the voyages that opened European maritime routes to India and Brazil — with the wealth, and the slave trade, that followed. The 1755 earthquake and tsunami destroyed much of the city and reshaped both its plan and European thinking about disaster. The estuary carried emigration outward and, after 1974, carried people back from the ending empire.

Timeline

Dates are shown on a timeline rather than as changing shapes on the map. The globe draws modern boundaries only, and tinting a modern outline to stand for a historical one would state something we cannot source.

Places that carry meaning

• The Tower of Belém1514–1519

  A fortified tower at the water's edge, built to defend the approach and to mark the point of departure. Inscribed as World Heritage with the Jerónimos monastery in 1983.

• LisbonContinuous

  On the north bank where the hills meet the water. Its shape — steep, terraced, with viewpoints — is a consequence of building a port city on that topography.

• The Tagus estuary reserveDesignated 1976

  One of the largest wetlands in western Europe, on the mudflats east of the city. A capital's estuary that is also a major flyway stop is an unusual combination to have kept.

Learn the language here

1. 1Understand which languages are spoken hereThe Tagus Estuary is multilingual. Start with which languages are used, by whom, and for what — the phrase list only covers one of them.Written by Globe Quest
2. 2Practise with people: Arabic practice · DohaAn in-person practice circle. It is a prepared plan and needs a host before it runs.Run by members

Check yourself

• What makes the Tagus estuary a good harbour?

  A wide sheltered basin behind a narrow, defensible, deep mouth near the open ocean

  Shelter without a long approach — which is exactly what an Atlantic voyage needs at both ends.

• What was new about the Baixa rebuilt after 1755?

  It used a timber cage frame designed to survive shaking

  Among Europe's first purpose-built earthquake-resistant construction, tested on mock-ups before use.

Worth arguing about

• The monuments at Belém commemorate departures. What would a monument to what the ships brought back look like?
• 1755 changed how Europe argued about disaster and providence. When does a catastrophe change how people think, and when does it not?

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