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Waitomo Caves
Waitomo, in the central North Island, consists of a 45 km (28 mile) network of underground limestone caves. The name Waitomo comes from the Maori wai, water and tomo, hole or shaft. Activities centre around a small village called Waitomo Caves (or simply Waitomo) where the Museum of Caves is the focal point.
The limestone in the Waitomo Glowworm Caves was formed
about 30 million years ago when Waitomo was beneath the sea...
Most of these are broken up by wave action into sand sized particles which gently settle on the seabed very slowly and at great depth. In some areas of Waitomo, the limestone is over 200 metres thick. The layering in limestone comes after deposition and does not relate to tides or seasons. These layers involve the dissolving and reforming of calcium carbonate in reaction with hard sand particles that do not dissolve in the seawater.
In the last 24 million years Waitomo has been going through much geological activity in the form of both earth movements and volcanic activity. Through this activity much of the hard limestone has buckled and bent and lifted up out of the sea. With this the limestone then separated into huge blocks allowing the rainfall to flow down cracks and joints. On the way down, the rainwater mixes with a small amount of carbon dioxide in the air forming a weak acid. The acid strengthens as more carbon dioxide is absorbed from the soil. As it seeps through cracks in the rock the acidic water dissolves the limestone and enlarges them. Eventually streams flow through the enlarged cracks helping to create the caves as we see them today.
Once the caves are formed, stalactites, stalagmites and other cave decorations begin to grow. Water dripping from the cave roof or flowing over cave walls leaves behind a deposit of limestone crystal. As time passes, these accumulate to form beautiful cave decorations. Stalactites form down from the ceiling and stalagmites grow up from the cave floor. When they join together they are called columns or pillars and where they spiral around they are called helictites. If there are other rock types above the limestone they will add minerals to the water and give colour to the formations called iron oxide. The iron oxide comes mostly from volcanic ash.
Black Water Rafting and Glow Worm Caves Tour
