Moeraki Boulders are large spherical boulders that are gray-colored septarian compactions disinterred from the bedrock and mudstone cliffs enclosing them.Local Maori legend explains that these boulders are the remains of calabashes, kumara, and eel baskets washed on the shore from the sinking of Arai-te-Uru, a large sailing waka (canoe). Most of them are spherical and are called ‘hooligan gallstones’ or ‘giant gobstoppers’ by locals.Moeraki Boulders are found in the coastal cliffs, on the beaches underneath the surface inland of the shore of the west coast of Northland, North Island, New Zealand, between Kauwhare and Koutu points. With a spherical shape and an unusually large size, two-thirds of these boulders range in size from about 4.9-7.2 ft (1.5-2.2 m), and the remaining ones are around 1.6-3.3 ft (0.5-1.0 m).Moeraki, also known as Moerangi, means ‘drowsy day’. The name, however, was kept after the local legends of a canoe that washed ashore from the wreck. Moeraki Boulders also occur as spherical cannonballs and flat, oval, or disk-shaped concretions.Location Of Moeraki Boulders BeachConcentrated on the beach by coastal erosion, the Moeraki Boulders are located on the wave-cut of New Zealand’s Otago coast along a stretch of Koekohe Beach between Hampden and Moeraki. It is about 24.9 mi (40 km) south of Oamaru and 46.6 mi (75 km) north of Dunedin along State Highway 1. Boulders are well known for their size range that goes up to 6.6 ft (2 m) in diameter.However, these boulders are not the only unique stones on the Otago coast. Other identical spherical boulders, called Koutu Boulders, exist on the shores of Lake Huron near Kettle Point in Ontario, in the sediment of the Kimmeridge Clay in cliffs by the edge of the Wessex Coast of England, within stratified rock outcrops in northeast Utah and central Wyoming, and at Rock City in Kansas.Likewise, on the north shore of Shag Point, about 12 mi (19 km) south of Moeraki Boulders, a similar boulder, called Katiki Boulders, is found. What’s more is that it is similar to large spherical concretions found in many other countries. Situated along a stretch of Koekohe Beach, some of these boulders contain the bones of mosasaurs and plesiosaurs.Origin Of Moeraki Boulders BeachThe huge spherical boulders are concentrations created by the diagenesis of the Paleocene mudstone of the Moeraki formation. The main landform of Moeraki Boulders was formed in the marine mud near the Paleocene sea floor surface. The Paleocene epoch is demonstrated by the composition of iron and magnesium, as well as stable isotopes of carbon and oxygen.These huge spherical rocks are spectacular examples of concretions formed approximately 60 million years ago by shoreline erosion of sedimentary rocks. For over 4 million years, mudstone with moderate precipitation of calcite has been formed as a consequence of Noah’s Flood, as concluded by creation geologists. Over time, the action of these waves eroded the softer stone to reveal the huge, giant one.These larger boulders are 6.6 ft (2 m) in diameter. They were estimated to have taken almost 4-5.5 million years to grow. There is 33–164 ft (10-50 m) of marine mud piled up on the sea level surface. There are over 50 boulders of different sizes on this beach, and one of them is at the Otago Museum. It is often said that these boulders will be extinct in 20,000 years due to the constant pounding of the Pacific Ocean, which is slowly disintegrating them.Sometimes people confuse these Moeraki Boulders with evidence of giant dinosaur eggs or alien remnants. However, its odd surface patterns and large size make it unique. It is also believed by Maori legend that the giant boulders along the Otago Coast of the South Island are remnants of baskets and gourds carrying eels and water in a double-hulled waka (canoe) called the Arai Te Uru, wrecked off Shag Point.However, the documentation of these Moeraki Boulders did not take place until 1814, when Europeans were involved during the ‘War of the Shirt’ or the Sealers’ War.Composition Of Moeraki Boulders BeachThe Moeraki formation is a compact mass of sedimentary rocks formed by a thick deposit of mudstone, clay, and silt.The outer shell of each Moeraki Boulder is hard and cemented by a mineral called calcite. The insides of these boulders are not so solid and were somehow eroded by the waves slamming against them, cracking them apart.The calcite mineral precipitated from the groundwater forms the spherical shape of a Moeraki Boulder. Detailed analysis using an electron microprobe, optical mineralogy, and X-ray crystallography determines that the outer rim consists of 10-20% calcite. Scientists often wonder why these round-shaped hardened masses of carbonate formed around dead organisms are typically in mudstone cliffs and marine mud.Basically, clay-rich and fine-grained rocks were characterized as being important to limit permeability, diffusion, and the migration of solutes to slow down. Many of these spheres display a turtle-like mosaic due to their cracked texture. These textures are called ‘septaria’ and outwardly radiate from a hollow core lined with a hemihedral crystal form of 8-12 faces. Several possible explanations have been proposed as to why the process of formation of such cracks has not yet been resolved.A typical boulder is coated with brown calcite on the outer layers and has a yellow calcite spar on the inner layers. Certainly, the rare ones have a very thin innermost layer of quartz and dolomite covering the yellow calcite spar. Each boulder weighs several tonnes and is up to 6.6 ft (2 m) high. Considering the height, it is often thought that these are visible during high tides. Although they are, only half of these boulders can be seen. The best time to appreciate its full size is during low tides, which occur twice a day. Light stormy conditions are also a good time to visit for a more scenic and atmospheric look at the boulders.One of the interesting facts about these boulders is that when they were first discovered in the 19th century, people used to take them home as keepsakes and garden decoration sets. Later, it became illegal to remove or take any of them. One of them is still missing from its place, as it is now in the Otago Museum in Dunedin.Besides, similar septarian concreted mudstone is found in Oxford Clay and Kimmeridge Clay in England, and many more places worldwide.Animals Found Near Moeraki Boulders BeachAt the southern point of the Moeraki Peninsula is the historic Katiki Point lighthouse. A trip to Moeraki would be incomplete without a stop at Katiki Point. The most noticeable tourist attractions here are the lighthouse, yellow-eyed penguins, and Te Raka, a Hineatea Pa site. Marine wildlife and birds can be spotted here as well.Moeraki Point is featured as an Important Bird Area (IBA) by Birdlife International and was granted such status due to the breeding of an endangered species, the yellow-eyed penguin, and a vulnerable species, the Stewart shag. However, this list doesn’t stop here. A variety of sea and shorebirds are spotted, such as sooty shearwater, little shag, little penguin, black shag, spotted shag, swamp harrier (kahu), variable oystercatcher (torea), south island pied oystercatcher, southern black-backed gull, sacred kingfisher (kotare), pipit (pihoihoi), gray warbler (riroriro), pied stilt, white-faced heron, and bellbird (korimako).Furthermore, the rock platform also supports a large colony of New Zealand fur seals, or kekeno. The main breeding area in north Otago has the most significant breeding site for fur seals, or kekeno.The Wildlife Management Reserve of Moeraki is quite a retreat for wildlife, as it acts as a protected area for these birds and animals to thrive while being eye candy for tourists. The Moeraki Boulders attract approximately 300,000 visitors each year. It is one of the natural wonders of New Zealand that is not only a must-visit place around New Zealand’s South Island along the stretch of Koekohe Beach, but is also free to visit.
Moeraki Boulders are large spherical boulders that are gray-colored septarian compactions disinterred from the bedrock and mudstone cliffs enclosing them.
