geology of madagascar
unlike the nearby islands, mauritius, reunion, rodrigues and the comoros, madagascar is not the product of volcanic activity although the volcanism is the source of some attractions and sights such as the amber mountain, the massif of ankaratra and lake itasy.
from geological point of view, madagascar is regarded as a continental island which owes its formation to the process of plate tectonic and continental drift. the theory of continental drift was developed by the german meteorologist wegener in the early 20th century. wegener noted that the contours of the coast of south america espouse those of africa. from that observation it was deduced that those two continents were part of a single one, a large continent, the gondwanaland, which broke away from an original super-continent pangea. the african continent, the island of madagascar, the south american continent, australia, antarctica and the indian sub-continent as we know them today were all part of the same continent gondwanaland over 200 million years (ma) before our era. africa, the island of madagascar, the south american continent, australia, antarctica and the indian sub-continent begun to break away from gondwanaland about 165 ma ago. madagascar became permanently an island about 65 ma ago.
2/3 of madagascar, mainly the eastern part of the island from north to south through the central highlands consist of crystalline basement formations mainly constituted of metamorphic rocks, the remaining 1/3 consists of sedimentary formations and occupies the western coast of the island from north to south. volcanic and intrusive basaltic formations complete the geology of madagascar and appear both at sea to form the island of nosy be, in the central regions, in the north and south of madagascar. each one of these formations is at the origin of rich mineral, fossil and serious signs oil basement in madagascar.