Caviana

Administratively, Caviana is part of the municipality Chaves in the Brazilian state Pará. The Equator runs through Outer Caviana, as does the 50th meridian west. It is the third-largest island in the Amazon Delta, after Marajó and Ilha Grande de Gurupá.

The island belongs to the Marajó Archipelago. It is located in the delta lowlands at the mouth of the Amazon, between the north coast of Marajó Island and the coast of Amapá. It is surrounded by Janaucu and Jarupari in the north, Mexiana in the east and the Jurupari Archipelago in the west. It is separated from Mexiana by the Canal Perigoso ("Dangerous Channel"), called such because sandbanks and strong winds make navigation perilous during low tides.^[1]

Just off Caviana's southern coast, where the South Channel (Canal Sul) of the Amazon meets the Vieira Grande Bay, is a sandbank called Camaleão that is exposed during low tide. It links together some smaller islets, such as Ilha das Pacas, Camaleão, Camaleãozinho and Jacuraru.^[1]

Geologically, Caviana is of mixed origin, made up of a combination of fluvial sediments and consolidated terrain.^[2] During the Tertiary epoch, Marajó, Caviana and Mexiana were connected to each other and to the mainland, forming a wide interfluve between the Amazon and Tocantins rivers. The continuity of the Barreiras Formation along the three islands is evidence of this, as are some palaeochannels that form continuous lines between them.^[3] The islands became separated through tectonic action during the Flandrian transgression at the beginning of the Holocene, some 12,000 years ago.^[4][5]

Caviana is located in an area where the strong current of the Amazon River meets the opposing pressure of the Atlantic waters, causing extreme turbulence, erosion, landslides and sedimentation. This encounter of water currents causes a distinctive tidal bore, which is called the pororoca.^[6] Caviana is known as a place to observe the pororoca and for some to surf on it.

The dynamism of wind, tides and currents gives rise to frequent changes in the topography of the Amazon Delta. Shorelines can change due to rapid sedimentation and erosion processes, and islands can split up or join together. On Caviana, this can be noted through the names by which local inhabitants refer to certain parts of the island, such as Ilha Nova or Ilha da Prainha (ilha = island), indicating that that these areas have been separate islands in the past, but have joined up with Caviana at some point.^[6]

A dramatic example of this dynamism occurred between 1845 and 1850 when a particularly strong pororoca made a breach in Caviana's coast, which already had been heavily eroded. The flood waters followed the course of a stream called Igarapê Guajuru, widening it until they had split the island in two. The parts, which continue to be separated to the present day, are named as follows:^[7]

• The smaller part with an area of 687 km² (265 sq mi) is called Inner or Northern Caviana (Caviana de Dentro or Caviana Setentrional)
• The larger part with an area of 2,257 km² (871 sq mi) is called Outer or Southern Caviana (Caviana de Fora or Caviana Meridional).^[8]

Caviana forms part of a biome called the Marajó várzea, which refers to the inundated land in and around the mouth of the Amazon River. The island is flat, marshy and frequently flooded, especially in the winter months. The eastern part of the island is made up of grasslands that are partially flooded in the wet season. The western side is covered with rainforest, which mostly consists of different varieties of palm trees.^[9]

Caviana is a birdwatchers' haven. As many as 145 different species were observed here. The ornithologist Joseph B. Steere observed the birds on the island in 1871, specimens were brought to the University of Michigan Museum of Natural History.^[10]

The island is contained in the 59,985-square-kilometre (23,160 sq mi) Marajó Archipelago Environmental Protection Area, a sustainable-use conservation unit established in 1989 to protect the environment of the region.^[11]

Caviana is of archeological significance. Excavations have been done on the island by Curt Nimuendajú in 1924–1925 and by Betty Meggers in 1948. All archeological sites are located on elevations in the landscape that are called tesos. Whether these elevations are natural or human-made is debated.^[6]

Evidence from these excavations suggests that the island was settled by indigenous groups in at least two phases. The first of these received the name "Caviana phase".^[12] The period in which these first groups settled on the island hasn't definitively been determined. Polychrome ceramics found from this phase are similar to those found in the north and south-east of the current state Amapá, suggesting this region as their origin.^[6][13]

The second phase of settlement, which extended into colonial times, is associated with the Aruã. Evidence found in the tesos indicates that they had much in common with other Arawak groups. This is apparent in the alignment of stones, polished statuettes, nephrite beads and amulets, ceramic figures, plates and roasters with dotted decoration.^[6] Findings in the tesos show that the Aruã practiced secondary burial in urns. Their cemeteries contain urns in different styles and also some glass beads and other European objects. This can indicate that Caviana was also inhabited by other groups, or that the Aruã traded intensively.^[14]