A satellite image of the mouth of the Amazon River, looking south

Date: 2015-10-07; view: 663.

Mouth

The definition of where exactly the mouth of the Amazon is located, and how wide it is, a matter of dispute, because of the area's peculiar geography. Some include the Pará River while other considered it the independent lower reach of the Tocantins River. The Pará river estuary alone is 60 km (37 mi) wide. The Pará and the Amazon are connected by a series of river channels called furos near the town of Breves; between them lies Marajó, an island almost the size of Switzerland that is the world's largest combined river/sea island.

If the Pará river and the Marajó island ocean frontage are included, the Amazon estuary is some 325 kilometres (202 mi) wide. In this case, the width of the mouth of the river is usually measured from Cabo Norte, in the Brazilian state of Amapá, to Ponta da Tijoca near the town of Curuçá, in the state of Pará. By this criterion, the Amazon is wider at its mouth than the entire length of the River Thames in England.

A more conservative measurement excluding the Pará river estuary, from the mouth of the Araguari River to Ponta do Navio on the northern coast of Marajó, would still give the mouth of the Amazon a width of over 180 kilometres (110 mi). If only the river's main channel is considered, between the islands of Curuá (state of Amapá) and Jurupari (state of Pará), the width falls to about 15 kilometres (9.3 mi).

Tidal Bore (pororoca)

The tension between the river's strong push and the Atlantic's tides causes a phenomenon called a tidal bore, known locally as the pororoca, in which the leading edge of the incoming tide forms a waves of water that travel upriver against the direction of the river's current. Tidal bores occur at the mouth of the Amazon and other nearby coastal rivers several times a year at high tide. Tidal bores also occur in other river around the world, but the Amazon's are among the world's highest and fastest, perhaps second only to those of Qiantang River in China. The pororoca flows up to 4 metres (13 ft) high and running at up to 13 miles per hour (21 km/h).

The pororoca occurs especially where depths do not exceed 7 metres (23 ft). It starts with a very loud roar, constantly increasing, and advances at the rate of 15–25 km/h (9–16 mph), with a breaking wall of water 1.5–4.0-metres (5–13 ft) high that may travel violently several kilometres up the Amazon and other rivers close to its mouth. It is particularly intense in the rivers of the coast of the state of Amapá north of the mouth of the Amazon, such as the Araguari River, but can be observed in Pará rivers as well.

The region near the Amazon's mouth also has very high tides, sometimes reaching 6 metres (20 ft) and has become a popular spot for river surfing.