Though Mauritius is volcanic in nature, with heaps of ups and downs, it is interesting to note that the area actually classified as ‘mountain’ occupies only 16% (300 km2) of the total surface area of the land. Here, mountains are low; the highest peak, Piton de la Petite Riviere Noire, measures only 828 m. A typical characteristic of the mountains on the island is the steep facade of the inner walls and the gentle spiky nature of the outer walls facing the sea.
The three mountain belts on the island, Port Louis – Moka Range, Black River – Savanne Range and the Bamboo Range, date to more than 7 million years ago. They actually represent the remnants of the original caldera of the volcano that formed the island. Notice the particular arc shape of the mountain belts. They are the inner walls of the caldera that spat out the lava to grow the rest of the land.
The Port Louis – Moka range consists of two prominent series of peaks. The first alignment consists of Pieter Both (820 m) and Mount Ory (320 m) and the second collateral peaks extend from Snail Rock to Virgin’s Peak. From Pieter Both, the belt sinks into the Deux Mamelles – Calebasses complex and then bulges again into the Nicoliere Mountains arc.
The mountain range is actually part of the original volcanic crater as it emerged from the sea during the Breccia series (7-10 million years ago). Climatic conditions, the type of volcanic materials and the vegetation played a major role in shaping these ranges. Weathering was the chief agent in shaping the slopes; basalt eventually skidded down due to gravity to form talluvium deposits.
The Black River belt represents the remnants of the main volcanic shield that formed Mauritius. It forms a continuous arc from Mount Rempart to Mount Canon; the highest peak of the island, Piton de la Petite Riviere Noire, 828 m, is located on this range. The mountain massif extends into the south-east to end in the Juracon Spur.
Much of the mountains are covered by thick olivine basalt from recent eruptions as well as basalt from the old series. The contact between these two lava series can be easily seen at Cascade Chamarel and Cascade Cecile. Intensive erosion and the flow of streams has created majestic peaks and clear-cut valleys.
Geographical studies of the mountain range have presented very useful information about the lagoon formation in the south-west. 18,000 years ago, sea level was 80-85 m lower than what it is today. The flanks of the caldera walls were above sea level and the whole side was exposed then. Soil profiles together with alluvial terraces and floodplains confirm this theory. During sea level rise and intense precipitation in the Holocene period, sea level rose up to what it is currently and eventually emerged the low lying areas of the volcanic slopes. The lagoon and coral formation were established on the wide eroded materials .
This thick massif marks the end period of the old volcanic series that created the isClae