Ribeira Principal

Ribeira Principal
The small valley (or dale) of Principal
Country	Cape Verde
Basin features
Main source	Serra da Malagueta Santiago Island, Cape Verde 900 m (3,000 ft)
River mouth	between Achada Fazenda and Pedra Badejo 15°12′15″N 23°40′07″W / 15.2043°N 23.6686°W / 15.2043; -23.6686
Basin size	16 km2 (6.2 sq mi)
Physical characteristics
Length	8 km (5.0 mi)

Ribeira Principal is a stream located in the mid-north of the island of Santo Antão in Cape Verde flowing exclusively in the municipality of São Miguel. The stream flows south in the southern interior and is about 8 km in length, the westernmost of the basin area is in the municipality of Tarrafal with two small streams emptying into Principal. The stream has some tributaries. During dry days especially in the Spring and Summer, the stream is predominantly dry. The Caminho de Ribeira Principal runs within much of the stream but not in the steepest areas at the uppermost part.

The etymology is being the main river of the north of the island, actually there are about five main rivers of the north pf the island, the others are Ribeira Grande do Norte de Santiago and Ribeira do Flamengos.

The stream starts in the Serra da Malagueta mountains inside its natural park and east of the municipality of Santa Catarina and the Praia-Assomada-Tararfal Road (EN1-ST01). The stream's source is around 900 meters elevation, it descends and flows north and then northeast at the area east of where the three municipalities meet. The river enters the village of Ribeira Principal and into one of its two settlements, Chão de Horta, also its river road runs on and within the stream, then it enters the village center Hortelão. The river flows left and then north at the area of Achada Monte and its settlement of Porto Formoso sobre Ribeira Principal, the river crosses Praia-Pedra Badejo-Tarrafal Road (EN1-ST02) and empties into the Atlantic a few hundred meters north.

Its geology of the dale or a small valley are a part of the Flamengos rock formation. It is composed of basalt, basanite and basanitoids out of volcanic eruptions of nearby Pico da Antónia or Serra Malagueta. Its rocks date to the miocene and pliocene periods. Its rock formation dominate the north of the island.

During the Ice Age, the stream was about a kilometer longer and was about 10 km it shortened to 17 km around 2000 BC. During the Ice Age, the river flowed around to the northeast for another kilometer from its current location before emptying into the Atlantic.