An island rising from the sea
The ground beneath Castlepoint Lighthouse is not static. The structure stands on the Castlepoint Formation, a section of early Pleistocene limestone and sandstone roughly 2.4 million years old. This entire landmass is being pushed upward by immense geological forces. It sits near the Hikurangi subduction zone, where the Pacific tectonic plate slides beneath the Australian plate. This ongoing collision actively compresses and lifts the eastern coast of New Zealand's North Island.
The limestone reef is packed with the fossilized remains of marine life, a direct record of its suboceanic past. The rock is a type of coquina, a limestone composed primarily of shell fragments and barnacle plates cemented together. These deposits formed in a submarine canyon at depths that may have exceeded 300 meters. Today, these same fossil beds are found 52 meters above sea level, a clear measurement of the tectonic uplift that has occurred over the last two million years.
The fossil assemblage is complex, containing species that lived in different ocean temperatures and depths. Geologists find fossils of shallow-water species mixed with deep-water organisms. This indicates that material from shallower ocean shelves periodically slid down into the deep canyon in submarine landslides, mixing the remains of different ecosystems. Fossils identified in the formation include the scallop Zygochlamys delicatula and early forms of the gastropod Pelicaria vermis, which confirm the reef's early Nukumaruan age (approximately 2.4 million years old).
A light on the land
The 23-meter-tall cast-iron tower was constructed to guide ships along the hazardous Wairarapa coast. Its sections were forged at a foundry in Wellington, shipped to the site, and assembled in 1912. The lighthouse was officially lit on January 12, 1913.
The original light source was an incandescent oil-burning lamp. This was replaced in 1954 with an electric lamp powered by a diesel generator, and in 1961 the lighthouse was connected to the main electrical grid. Today, its light comes from a 1000-watt bulb inside the original second-order Fresnel lens. This is one of only two lighthouses in New Zealand still operating with its original lens. The apparatus produces a distinct pattern of three white flashes every 30 seconds, visible for up to 26 nautical miles (48 kilometers).
For 75 years, the lighthouse required keepers to operate and maintain the light. It was a popular posting, nicknamed "The Holiday Light" because of its proximity to the Castlepoint settlement, unlike more isolated stations. In 1988, the station was fully automated and is now monitored remotely by Maritime New Zealand in Wellington.
The surrounding reef and waters host a variety of marine life. New Zealand fur seals (Arctocephalus forsteri) are often seen on the rocks. Several species of dolphins visit by several species of dolphins, and occasionally larger marine mammals like southern right whales and humpback whales during their migrations. The only place to find the rare Castlepoint daisy (Brachyglottis compactus) is on the crumbled limestone of the reef and Castle Rock.