Ankarana Special Reserve in the northern region of Madagascar was developed in 1956. It is usually a small, partially vegetated plateau made up of 150-million-year-old middle Jurassic limestone. With an average annual rainfall of about 2, 000 millimeters (79 in), the underlying rocks are vulnerable to erosion, therefore generating caves as well as underground rivers—a karst topography. The rugged relief and the dense vegetation have helped protect the region from human intrusion.
The plateau slopes gradually to the east, however on the west it ends up abruptly in the "Wall of Ankarana”, a large cliff that extends 25 kilometers (16 mi) north to south, and rises as high as 280 meters (920 ft) . To the south, the limestone mass breaks up into separate spires known as tower karst. In the center of the plateau, seismic activity and eons of rainfall have dissolved the limestone away in deep gorges, and sometimes redeposited it in ribbons of flowstone. In places where the calcific upper layers have been completely eroded, the harder base rock has been etched into channels and ridges known as Tsingy.
