Travel Reference
In-Depth Information
The roc as visualised by an artist in 1598
BiodiversityHotspotscoverlessthan1%oftheearth'ssurface,yetarehometowellover
halfofitsplantandanimalspecies.AlthoughitisnotentirelyunderstoodwhyMadagascar
has so many species, two factors have helped: it is near to the Equator and it contains an
astonishing array of habitats. The tropical climate is a perfect host to the processes of life
- far more living things survive within the tropics than in cooler regions - and the habitat
variety provides greater opportunity for animal and plant variation.
GEOLOGY
With information from Tim Ireland
The story of Madagascar's astonishing natural history begins millions of years ago. The
island's geology raises plenty of interesting questions - many still unanswered - and at-
tracts geologists and mining companies from around the world. Madagascar comprises
three main geological terranes: a
crystalline core
comprising the central highlands, a
sed-
imentary shelf
that flanks this core on the west, and dispersed
volcanic edifices
.
The
crystalline core
dates to the Late Proterozoic, 900-550mya (million years ago), a
period long before the evolution of complex life, and before the assembly of the continents
asweknowthem.Yettheserockscontaintinycrystalsofzirconwhichtestifytoafargreat-
er antiquity (2,600mya). It is thought that this zircon records the formation of a continent
that would later become part of Gondwana. Other continental masses also existed, sever-
al that would later become the northern continents, and one that would split and become
South America and Africa.
Two of these (South America-Africa and Australia-Antarctica-India-Madagascar) had
beendriftingslowlyclosertogetheruntiltheycollided690mya,justasthefirstlargemulti-
cellular marine creatures were beginning to evolve. During such collisions the edges of the
continents crumple and sheets several kilometres thick are thrust over each other forming
mountain ranges. The so-called Mozambique Belt of mountains was immense, extending
7,000km from present-day Kenya down to Antarctica, with Madagascar right at the centre.
The rocks buried during mountain-building are recrystallised and partially melted under
the intense pressure and heat. The central highlands of Madagascar are just a small part
of the exhumed roots of this vast and ancient mountain belt, consisting of recrystallised
rocks such as gneisses, granulites, migmatites and granites. The ramparts of the Mozam-
bique Belt then stood sentinel, slowly eroding but largely unchanged, for several hundred
