Candidatura Reserva da Biosfera - Santana Madeira Biosfera

11.4. GEOLOGY, GEOMORPHOLOGY, SOILS
The genesis of the archipelago is related with the opening and expansion of the
Atlantic Ocean, which begun at 200 million years (m.y.) ago in the Triassic period, which
still continues to the west and east of the Mid-Atlantic Ridge, at an average of 1.2 cm per
year. The Madeira is located on the African tectonic plate on a substrate whose oceanic
crust has an estimated age of 115 m.y.. Madeira is the latest expression of volcanism of
the “hot spot” responsible for the genesis of the Madeira volcanic chain, which comprises
the islands of Madeira, Deserts, Porto Santo and the Dragon, Lion, Josephine, Ashton,
Seine, Ormonde and Tore submarine elevations. Taken together, the Madeira-Tore
oceanic ridge, of NE-SW orientation, extends for 1400 kilometers to the meeting line
between the African and Eurasian plates, constituting its SW extreme the Madeira island,
aged approximately 5 m.y. and its NE extreme the submarine mountain Tore aged
approximately 95 ma. The model of the geological evolution of the islands is in itself
demonstrative of the trail of activity of the Madeira "hot spot", whereas the
volcanological age of Porto Santo Island is 14 m.y., while the island of Madeira located
40km SW of Porto Santo, is only about 5 m.y.. Despite the last records of volcanic
activity in the archipelago have occurred about 6000 years during the recent volcanic
episodes, characterized by Strombolian eruptions located in Funchal, Porto Moniz and
Paúl da Serra, during the construction of the tunnel between the Rosário and Serra de
Água, carbogas spring waters were found at about 75 °C. These secondary volcanic
events show that the volcanic activity on Madeira is undergoing a period of dormancy
and isn’t extinct.
72 Application of Santana, Madeira to Biosphere Reserve – UNESCO - MAB