Santo Antão, Cape Verde
Santo Antão (Portuguese for Saint Anthony ) is 779 km ² the second largest of the Cape Verde Islands in the Atlantic. On Santo Antão 47,124 people live.
Geography
The predominantly rural island belongs to the northern group of islands Ilhas de Barlavento (German: " Leeward Islands " ) and is separated by a 16 km wide sea channel of lying in the south island of São Vicente.
The hochgebirgige volcanic island is known for its impressive mountain ranges with deep erosion valleys to the north and to the south a little flatter expiring volcanic slopes. Young volcanoes with broad Caldeira, sprawling white shiny pozzolana hills and hundreds of meters high basalt rocks form dramatic volcanic landscapes. On the heights of the eastern plateau are the largest mixed and coniferous forests of Cape Verde. The northeast of the island is relatively rainy, while the Southwest will remain dry. The highest elevation is the Tope de Coroa (1979 m) in the desert west.
Administratively, the island is divided into three Concelhos ( counties ), Paul, Porto Novo and Ribeira Grande. The port city of Porto Novo in the south has the traditional Vila da Ribeira Grande expired a few years ago as the most populous settlement of the rank.
Geology
The geological development Santo Antãos can be divided into three phases ( from young to old):
- Young volcanics
- Intermediate volcanic rocks
- Old volcanic rocks
The lying below sea volcanic base of the island is expected to about 16 million years BP go back ( beginning of the Middle Miocene - Langhium ). It accounts for about 50 % of the total and is 119-118 million year old oceanic crust from the Lower Cretaceous ( Aptian ) on. The above ground open-minded old volcanic rocks date back to the Tortonian (before 7.5 million years BP), the majority of the sequence is depreciated over 3 to 2 million years BP old (Upper Pliocene - Piacenzium and Gelasian ). The predominantly subaerisch flowed out old volcanic rocks form a large complex, which reached from Cha Morte the valleys of Escabecada, Tarafal, Agua Nova and Cha de Igreja. The volcanic rocks belong to the basanite / tephrite / phonolite Differentiationsreihe, where basanites predominate clearly. Enriched basanites are in the lower Agua Nova Gorge. The old volcanics were funded over a southwest-northeast - trending vein swarm, which crosses the central portion of Cha Morte and the northern Ribeira Grande Valley.
Figures 2 to 0.3 million years BP old intermediaries volcanic rocks of the Quaternary (early and middle Pleistocene ) can be divided into five groups:
- Agua Nova Group
- Monte Frado Volcano
- Sinagoa Volcano
- Cova Group
- Bordeira Group
In them occur for the first time the rocks more enriched nephelinite / phonolite Differentiationsreihe on ( with Melilithnepheliniten, Nepheliniten and phonolites ). Figures 2 to 1 million years BP old, altpleistozäne Bordeira group consists of a nephelinitischen Vulkanbau who built in the western part of the Cha Morte over a flattened volcano the old volcanic rocks. The 1.4 to 0.7 million years old Cova Group ( also Early Pleistocene ) is basanitisch and open-minded in the Cova / Corda / Paul sector. Between 0,7 bis 0.3 million years BP Sinagoa the volcano emerged in the central highlands with the Cadela - volcanics. The nephelinitischen and basanitic volcanics were promoted over a column that had opened parallel to the southwest of the old gear swarms. Between 0.5 and 0.4 million years BP the basanitische Monte Frado - volcano erupted in the south of the island at about the same time came the volcanic rocks of the basanitic Agua Nova Group, which still survived to 0.3 million years.
0.4 to 0.1 million years BP old and predominantly nephelinitischen ( Medium to Upper Pleistocene ) younger volcanic rocks can be divided into four groups:
- Lagoa Group
- Coroa Group
- Young Tarafal Group
- Proto - Coroa Group
400000 bis 200,000 years BP old proto- caroa Group with its nephelinitischen Scoriakegeln and lavas can be found in the vicinity of the Tope de Coroa. In about the same time of the Tope de Coroa was erupted the boy Tarafal group west across the southwest-northeast - trending column systems, which also has nephelinitischen chemistry. Between 200,000 and 170,000 years BP nephelinitischen the lavas of the Coroa group were encouraged; they overlap to some extent the proto- Coroa group.
In the period 400000-100000 Jahre BP penetrated in the central part of the island via column systems nephelinitische Lagoa - group. In the central highlands as developed along the column several strings of Scoriakegeln. From the columns of lava flowed to the southeast and reached west of Porto Novo the sea.
Years ago, about 200,000 BP occurred over a vent just south of the Coroa complex in the West Santo Antãos a larger Plinian eruption that left two phonolithische Bimshorizonte (CG 1 and CG 2). The first horizon covered the entire island and is therefore suitable for stratigraphic correlations of the younger lavas of great value.
The majority of Vullkanite Santo Antãos consists mainly of lava flows of the two already mentioned Differentiationsreihen. 10 to 20 % of the lava flows are composed of Pikriten and Ankaramiten. In the vicinity of the eruption centers, but often also pyroclastics, mainly lapilli and bombs. Even some ignimbrites are present. In volume terms, the most significant among the eruptions, however, was undoubtedly the phonolithische pumice from Cão Grande.
Petrological model calculations refer to a heterogeneous, peridotitisches mantle rock, the aufschmolz partially in 90 to 125 miles deep to 1-4 %. The primitive Magmentypen under the conditions found on Santo Antão volcanic rocks are typical, dominated by a HIMU oceanic island basalts component (OIB ). The older volcanics vary between a boy and a slightly less radiogenic HIMU component. The intermediaries volcanics represent a two-component mixture of a DM- like component and the carbonatites related, young HIMU component dar. For the boys volcanics dominated an old HIMU component. It is believed that the magmas ascended to the Cape Verde mantle plume, the temporal changes in the chemical composition are ascribed to an internal composition change of mantle plumes.
History
Taken as early as 1462 by Diego Afonso of Portugal in possession, the island was initially mainly used for harvesting the dyer rosela tinctoria. Only in the 17th century it came to permanent settlement by the sons of landowners in the southern islands of Santiago and Fogo, as well as by new settlers from the north of Portugal, under the Count da Cruz in today's Vila da Ribeira Grande. Wine, Purgiernüsse and later coffee were the main export products, which determined the history of the island.
Economy and Tourism
The main economic activities are agriculture with the cultivation of sugar cane, yams, cassava, banana, mango and corn and fishing. The most important agricultural product is now the Grogue called white rum of the island.
In the north, tourism plays an increasing role slowly. Santo Antão, with its impressive mountain scenery is the most popular island of Cape Verde for hiking with Vila da. Ribeira Grande and Ponta do Sol as a starting point for extensive tours For swimming and fishing especially Tarrafal de Monte Trigo offers.