You have arrived at Veimumuni Cave - full of local folklore and oral history. Read the sign at the parking lot about a beautiful Tongan woman, Vei, and a mischevious spirit named Muni.
Coral limestone is formed over thousands of years, as coral polyps extract calcium and carbonate ions from seawater to build skeletons of calcium carbonate. As corals die, their rigid, reef-building skeletons accumulate, break down into debris, and undergo lithification (cementation) into solid, dense rock in warm, shallow, marine environments. Key processes in Coral Limestone formation:
- Bilogical Secretion: coral polyps (tiny animals) build their skeletons by secreting calcium carbonate, creating the foundational structure of the reef.
- Accumulation: as corals reproduce and die, new generations settle on the hard, calcium-rich skeletons of their ancestors, building layer upon layer o fmaterial.
- Lithification (Cementation): the accumulation of coral skeletons, along with shell debris, algae, and other marine organisms, breaks down and cements together to form limestone.
- Environmental Factors: formation requires clear, warm, shallow water (typically less than 150 meters or 492 feet) to allow for photosynthesis, necessary for coral's survival.
- Time: reef building is a slow process, with structures growing vertically at rates of only 1-25 centimeters per year (10 inches, at the top end of the scale), taking millennia to form large limestone deposits. The resulting rock, often found in fossilized form on land, can be classified as a biogenic - or organic - limestone, composed primarily of skeletal fragments.
Veiumuni Cave is a perfect example of how uplifted coral limestone, tropical rainfall, and karst process combine to create freshwater caves. It also shows how geology and culture intertwine in Tonga's landscapes.
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1. Stand at the entrance and examine the limestone walls. In your own words, describe: the texture (smooth? pitted? sharp?), and whether the rock looks eroded by water, broken by collapse, or both.
2. Observe the freshwater pool. What color is the water and how clear is it? Based on what you see, what does this suggest about how water moves through limestone?
3. Proof of visit: please post a photo of yourself, or a personal identifiable object such as your caching name, at the site of the earthcache without giving any spoiler information in the background. We love to hear your stories!
This cache is not wheelchair accessible, but it is not difficult to go down the concrete stairs from the parking lot, and navigate to the "pier" at the mouth of the cave. The cave entry itself does require some bending over (so as to not hit your head), and 6 to 8 wooden stairs.