The tsingy
The madagassic word tsingy means "on the toe points go". Indeed, the knife-sharp rocks in the tsingy almost prevents from walking bare foot.
You will discover a wonderfull area, with spectacular geology, and a unique fauna including lemurs.
Chronology of Tsingy
Between 160 and 10 million years, the sedimentation:
Under the Sea, which opens gradually between Africa and Madagascar, shells and dead coral pile slowly and fuse into limestone to form a thick layer.
Between 10 and 6 million years ago, the emersion:
Limestone rocks, thick several hundred meters, fellow the slow uplift of the island and gradually move out of the water. By raising, these rocks are subjected to enormous pressure and crack.
4 million years, laterite cover:
During a particularly wet period, erosion attack basalt rocks of the backbone of the island. Residues, laterite settle the limestone bed. On the occassion of the rainy season which led to profound changes, karstification, begun in the emersion of limestone, continued in rock under the cover of laterite.
3 million years, removal of the laterite:
During a wet period, the laterite layer that covers the limestone is cleared. The erosion of limestone continues on surface and underground.
2.5 million years to the present time, the climate change:
The landscape is changing during successive climatic phases: tropical wet, tropical desert, tropical in alternating seasons. Erosion and corrosion gradually sculpted limestone to reach the current shapes.
The genesis of Tsingy
It is water that has shaped the karst landscape on surface and underground (caves and canyons). Water penetrates limestone thanks to the existing cracks. Then the cracks are progressively extended and become well and galleries.
Rainwater is combining with carbonic acid in contact with air and soil. It attacks and dissolves the limestone (chemical erosion). The more limestone is cracked, the dissolution is more rapid and more shapes are spectacular.
Essential factors to the formation of Tsingy:
- High purity and low porosity limestone
- A significant fracturing
- The inclination of the layers should be low, below 5 °
- No freeze
By observing the limestone cliffs, one can notice the horizontal cracks, vertical or oblique cracks and flaws. Horizontal cracks are bedding planes, due to a change in the nature of sedimentary deposits. Vertical or oblique cracks are called joints. They are in the interval between bedding planes. The faults are deeper fractures that affect multiple bedding planes and are large-scale phenomena.
The earth cache
Access to the cache
The cache is located near the top of Grand Tsingy de Bemaraha.
The Park is only opened during the dry season from April to November, since it is inaccessible during the rainy season (mid-end November to mid-end May). The Grand Tsingy are only accessible between June and the beginning of November.
The access is quite tough:
- the Park entrance is located in the village of Bekopaka (from Belo-sur-Tsiribihina: only very bad secondary roads)
- from Bekopaka, about 1.5 hour of bad track in 4WD vehicle to reach the entrance to Grand Tsingy
- about 3km hiking/climbing to discover the Grand Tsingy. It takes between 4 and 6 hours.
You will have to pay for the park fee, and the ranger (mandatory) who will guide you.
Climbing gear provided at park entrance.
You will need good shoes, and a flash light.
[EN] To log the cache:
In order to validate the log, please complete the following tasks (send me an email, or a message in Message Center, with the answers to questions).
- Close to the cache, you will see some evidences of limestone bedding planes.
What are those evidences ? Can you estimate the current height of the top bedding plane ? Please explain how you estimate it.
- At the cache coordinates, you will see a rock with a painted sign.
- What is the width of the small grooves visible on the rock next to the sign ?
- According to you, what kind of erosion can be seen on the rock next to the sign ?
- In your log or in message, provide a picture of you or your GPS device in the tsingy
The logs will be deleted if answers are not sent!
Enjoy the Tsingy !!
[FR] Pour signer la cache:
Pour valider la découverte de la cache, les taches suivantes devront être réalisées (les réponses aux questions me seront envoyées par email):
- A proximité de la cache, des plans de stratification calcaire sont visibles.
Comment peut-on identifier ces plans de stratification ? Quelle est l'épaisseur actuelle du plus haut plan de stratification ? Expliquez votre manière de mesurer.
- Aux coordonnées de la cache, un signe est peint sur le rocher.
- Quelle est la largeur des rainures visibles juste à coté du signe ?
- Selon vous, quel est le type d'érosion visible juste à coté du signe ?
- Dans votre log ou dans un message, attachez une photo de vous ou de votre GPS dans le tsingy.
