The Baía de São Marcos is a bay of the
Atlantic Ocean
The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...
in
Maranhão
Maranhão () is a States of Brazil, state in Brazil. Located in the country's Northeast Region, Brazil, Northeast Region, it has a population of about 7 million and an area of and it is divided into 217 municipalities. Clockwise from north, it ...
state of northeastern
Brazil
Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...
.
The bay is an estuary approximately long and up to wide. It receives several rivers, including the
Grajaú,
Mearim, and
Pindaré. The Mearim is known for its
pororoca
The Pororoca (, ) is a tidal bore, with waves up to high that travel as much as inland upstream on the Amazon River and adjacent rivers. Its name might come from the indigenous Tupi language, where it could translate into "great roar". It could ...
, or
tidal bore
A tidal bore, often simply given as bore in context, is a tidal phenomenon in which the leading edge of the incoming tide forms a wave (or waves) of water that travels up a river or narrow bay, reversing the direction of the river or bay's cu ...
.
São Luís Island, also known as Maranhão Island, separates the Baía de São Marcos from the
Baía de São Jose just to the east. São Luís Island is home to
São Luís, Maranhão's capital.
Estuaries of Brazil
Landforms of Maranhão
Bays of Brazil
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