The Amboni Caves are situated at a locality known as Kiomoni past Kiomoni village about eight kilometers to the north of Tanga, off the Tanga Mombassa Road. The caves have been formed naturally in the tanga limestone series which is of Jurassic period ( about 150 million years ago). According to researchers the area was under water some 20 million years ago, and it is estimated to extend over an area of 234 square kilometers.

These caves have been subject of local legends and a number of mythical and awe-inspiring stories have been attributed to the caves. To the local people the caves are regarded as supernatural formations where supernatural powers commonly known as "Mizimu" are believed to have been residing since the caves formation. There are chambers treated as sacred chambers for worshiping some spirits. One of them is called "Mzimu wa Mabuvu". Some believe that there is a powerful deity which can alleviate their sickness, sufferings or increase their fertility.

It is not known when the caves were exactly discovered but reports indicate that ethnic groups such as Bondei, Sambaa. Digo, and Segeju who lived near the caves have been using them for prayers or worshiping spirits since the 16^thCentury.

The area was quired in 1892 by "Amboni Limited" a foreign company who operated sisal plantations in the Tanga region. The company notified the British colonial government about the caves who in turn declared them a conservation area in 1922. Since 1963 the department of Antiquities is managing the caves and in 1964 the Antiquities act was passed to protect all antiquities in the Country. It is therefore unlawful so leave a trace or to inscribe on the cave walls.

These limestone caves are formed by a special nature of erosion. According to Mturi (1975:18-19), there are tree theories which explain the formation of the Amboni Caves.

The first theory is known as the vedose process. According to this theory, rain water absorbs carbon dioxide in the atmosphere and forms a weak carbonic acid which is capable of dissolving calcium carbonate minerals of which limestone is formed. When this acidulated rain water seeps trough the limestone it is dissolved and cavities and caves are formed.

The second theory is that of phreatic origin. According to this theory, the caves are formed by erosion from the sub water table. The rain water with carbonic acid rapidly seeps through the limestone and reaches the water table before being a saturated solution of calcium bicarbonate. At this stage it is still capable of acting as a dissolving agent for the calcium carbonate. As the groundwater is moving slowly along joints and shale partings between the limestone beds dissolving the calcium carbonate and thus forming channels. As channels grow. the flow of water becomes turbulent and this speeds up the dissolution process. The channels are consequently enlarged into passages and a network of solution passages are formed. At the junction of major joint systems, these may be enlarged to become caverns. This process only stops when the water table is lowered which leaves the cavern dry, while the dissolution process continues at a lower level.

The third theory is that of the sea wave action. This is based on the assumption that the area in question at a particular time was along a shoreline and therefore subject to wave action. The waves gradually eroded the limestone forming caves. Afterwards the fall in the sea level left the caves dry.

It is most likely that all three processes contributed to the formation of the Amboni caves.

Adapted extract from the following sources:
Mapunda, Bertram Baltasar and Paul Msemwa 2005 Salvaging Tanzania's cultural Heritage, Dar-es-Salaam. Dar-es-Salaam University press.
Mturi, A.A. 1975 A guide to Tongani Ruins, Dar-es-Salaam.
Smith, A. 1963 The Amboni Caves. A third Theory, Tanganyika Notes and Records No. 61: pp. 195-204

More history about Tanga
Urithi Tanga Newsletter Vol 1
Urithi Tanga Newsletter Vol 2 September 2001
Archaelogical Reconnaissance of the Mkulumuzi and Sigi River Valleys.
Amboni Caves and Mkulumuzi River Valley.

Speleology