A volcanic plug , also called a volcanic neck or lava neck , is a volcanic object created when magma hardens within a vent on an active volcano. When present, a plug can cause an extreme build-up of high gas pressure if rising volatile -charged magma is trapped beneath it, and this can sometimes lead to an explosive eruption. In a plinian eruption the plug is destroyed and ash is ejected.
23-507: The Hūnua Falls are on the Wairoa River in the Auckland Region of New Zealand , near Hūnua . The land around was bought by Auckland for water supplies between 1940 and 1960. The mean flow of water downstream at Clevedon is 2.6 m (570 imp gal)/s, but can vary greatly, as illustrated in photographs showing the falls in winter and summer . The Wairoa River falls over
46-474: A basalt lava plug . Volcanic tuff rings and lava bombs are visible in the east wall of the waterfall. Several herbs have been identified near the falls - water starwort ( Callitriche petriei), Crassula hunua, water pennywort ( Hydrocotyle microphylla), wood-sorrel ( Oxalis magellanica ). The Wairoa has smaller falls. Lily Falls (also known as Wairoa Falls) were described as 70 ft (21 m) high and 3 mi (4.8 km) downstream from Hūnua, in
69-580: A similarly named river in Tahiti . Te Wairoa was a name applying to the river mouth and surrounding area, while Ōtau referred to the upstream areas further, including where the river passes by Clevedon . The early Tāmaki Māori hapū of the Wairoa river valley between the 14th and 16th centuries included Te Ngungukauri, Te Uri Kupai, Ngāti Ruangaingai and Ngāti Parahanga, who identified as both Ngāti Tai Manawaiti, and Ngā Iwi ( Waiohua ). The related hapū were united under
92-646: Is the second longest river in the Auckland Region of New Zealand 's North Island . It flows south from its sources in the Hunua Ranges , then northwards into the Hauraki Gulf . The Wairoa Reservoir and Hūnua Falls form sections of the river, and the Wairoa River flows adjacent to the township of Clevedon . The river begins in the central Hunua Ranges , flowing south to the Wairoa Reservoir, and once exiting
115-671: The Caribbean . Pinnacle Rock, Galápagos, Ecuador . There are several volcanic plugs in the North Island of New Zealand , including: In New Zealand's South Island , Onawe Peninsula on Banks Peninsula is a prominent volcanic plug, and erosion of Saddle Hill near Dunedin has also revealed a plug. Dunedin's Mount Cargill displays two plugs: its main summit and the subsidiary summit of Buttar's Peak. In Australia , The Nut in Tasmania are further examples, along with Mount Warning and
138-708: The Garajonay National Park . Sigiriya is an ancient rock fortress near the town of Dambulla in Sri Lanka . Approximately 180m high, it is now a UNESCO listed World Heritage Site . Borgarvirki is a volcanic plug located in north Iceland. A volcanic plug is situated in the town of Motta Sant'Anastasia in Italy. Saint Michel d'Aiguilhe chapel, whose construction started in 969, near Le Puy-en-Velay in France. The volcanic plug rises about 85 metres (279 ft) above
161-736: The Invasion of the Waikato , Ōtau was attacked by the British army, and the village was evacuated. After which, the residents moved to live in communities at the river's mouth. For the remainder of the war, Ngāi Tai were designated as a "friendly" people by the Crown, and remained neutral in the fighting. After the Native Lands Act of 1865, the Native Land Court individuated the collective Ngāi Tai lands, and in
184-608: The Northern Cordilleran Volcanic Province gives rise to several confirmed and suspected plugs. Chief among these is Castle Rock , located in British Columbia , which last erupted during the Pleistocene . The southern coast of Saint Lucia is dominated by the iconic Pitons , a UNESCO World Heritage Site . The twin peaks, Gros Piton and Petit Piton, steeply rise more than 770 metres (2,530 ft) above
207-863: The United States , including Morro Rock in California , Devils Elbow located in the Heceta Head Lighthouse Scenic State Park on the Oregon coast, Thumb Butte in the Sierra Prieta of Arizona, and Shiprock in New Mexico . Devils Tower in Wyoming and Little Devils Postpile in Yosemite National Park , California, are also believed, by many geologists , to be volcanic plugs. In Canada,
230-542: The Waikato . In 1836, Fairburn purchased 40,000 acres between Ōtāhuhu and Umupuia ( Duders Beach ), including much of the catchment of the Wairoa River. Fairburn's Purchase was investigated by the New Zealand Land Commission in 1841 and 1842 and found to be excessive and reduced in size. The disallowed parts of his purchase were not returned to Ngāi Tai, however in 1854 a reserve was created for Ngāi Tai between
253-427: The rangatira Te Wana in the early 18th century, under the name Ngāti Tai (now more widely known as Ngāi Tai ki Tāmaki ). The river mouth formed the traditional heartland of Ngāi Tai ki Tāmaki. Ngāi Tai peoples traditionally lived in seasonal cycles, focusing on fishing and shellfish collecting, cultivations and collecting berries and snaring birds in the river's upper reaches, depending on the season. The river-mouth
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#1733084539949276-530: The Hunua Ranges changing course to flow northwards. Paparimu Road and Hunua Road follow the course of the river as it flows northwards through farmland. Much of the western Hunua Ranges flows into the Wairoa River, including Cosseys Creek and the Ōtau Valley, both of which have been dammed as freshwater reservoirs. In addition to these, the Wairoa River is joined by other tributaries: the Mangawheau Stream,
299-791: The Hunua Stream which flows past the settlement of Hūnua , and the Taitaia Stream, which meets the Wairoa River north of Clevedon . Past Clevedon, the river veers north-east, meeting the Urungahauhau Stream and the Aroaro Stream of the Ness Valley and forming an estuary . The estuary reaches the Hauraki Gulf at Pouto Point in the east. The river first formed during the Pliocene era, approximately 3 to 4 million years ago. Originally it
322-614: The Wairoa Gorge. A photograph appeared in 1901. As well as tracks to the Hunua Ranges , there are two 30 minute walks; The Lookout Walk and the Upper Lookout Walk . The cliffs are used for abseiling . This waterfall -related article is a stub . You can help Misplaced Pages by expanding it . This Auckland Region -related geography article is a stub . You can help Misplaced Pages by expanding it . Wairoa River (Auckland) The Wairoa River , also known as Wairoa South ,
345-428: The Wairoa River won a New Zealand River Award for being the most improved river in the Auckland Region . The lower Wairoa River north of Clevedon is navigable by boats and canoes. Volcanic plug Glacial erosion can lead to exposure of the plug on one side, while a long slope of material remains on the opposite side. Such landforms are called crag and tail . If a plug is preserved, erosion may remove
368-527: The eastern shores of the Wairoa River and Maraetai / Umupuia . From 1854, European farming settlers began to arrive on the banks of the Wairoa River, forming the township of Clevedon . Ngāi Tai held a defended settlement on the eastern banks of the Wairoa River opposite Clevedon, known as Ōtau. During the first decade post European settlement, Ngāi Tai and the European settlers had cordial relations, trading goods and assisting each other. In September 1863 during
391-594: The first crop of potatoes grown in New Zealand, and three years later, potatoes were gifted during a feast at Te Hūnua to the tribes of the Hauraki Gulf and Waikato, becoming some of the first varieties of rīwai ( Māori potatoes ) in New Zealand. When William Thomas Fairburn visited the area in 1833, it was mostly unoccupied due to the events of the Musket Wars , as most members of Ngāi Tai had fled to temporary refuge in
414-503: The process the majority of land near the Wairoa River was alienated and sold to European farmers. During European settlement, most of the Wairoa River catchment was deforested. In the early 1900s, the river mouth became popular with Auckland residents for duck shooting and picnicking. In 1955, the Cosseys Creek Dam was constructed in the Hunua Ranges, a rolled earth dam constructed to secure fresh water supplies for Auckland . This
437-593: The surrounding rock while the erosion-resistant plug remains, producing a distinctive upstanding landform. Near the village of Rhumsiki in the Far North Province of Cameroon , Kapsiki Peak is an example of a volcanic plug and is one of the most photographed parts of the Mandara Mountains . Spectacular volcanic plugs are present in the center of La Gomera island in the Canary Islands archipelago, within
460-1287: The surroundings. Another building on a volcanic plug is the 14th century Trosky Castle in the Czech Republic . Strombolicchio , the northernmost of the Aeolian Islands , and Rockall , a small, uninhabited, remote islet in the North Atlantic Ocean , are also volcanic plugs. In the United Kingdom , two examples of a building on a volcanic plug are the Castle Rock in Edinburgh , Scotland, and Deganwy Castle , Wales . The Law, Dundee , Ailsa Craig , Bass Rock , North Berwick Law and Dumgoyne hill are other examples of volcanic plugs located in Scotland . There are over 30 volcanic plugs in Northern Ireland , including Slemish in Ballymena , Tievebulliagh , Scawt Hill , Carrickarede , Scrabo and Slieve Gallion . There are several volcanic plugs in
483-634: Was a westwards-flowing river, flowing into the proto- Manukau Harbour past Weymouth . Much of the river flows along the Wairoa River Gorge, formed along a fault line. The Hunua Falls , a 30 metre high waterfall, flows overtop of an ancient volcanic plug . The Wairoa River's traditional name, Te Wairoa ("The Great River") was named by early Ngāi Tai ki Tāmaki ancestors of the Tainui waka, referencing Te Vairoa in Rarotonga , which in turn took its name from
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#1733084539949506-608: Was joined by the Wairoa Ram in 1975. The construction of the dams significantly reduced the flow of the Wairoa River. In 2002, the Auckland Regional Council began developing a management strategy for the river, with was further developed in 2016 with the founding of the Wairoa River Steering Group, now a part of the volunteer conversation group Friends of Te Wairoa Catchment, which formed in 2017. In 2017,
529-499: Was used as a summer pioke ( Shortspine spurdog shark) fishing ground, which were dried for the winter months. Ngāi Tai settled at many pā and kāinga along the river, especially at the river's mouth. In November of 1769, Captain Cook visited the Hauraki Gulf area. Cook gifted potatoes to senior members of Te Uri ō Pou from Ōrere , who then planted these at Te Hūnua, along the Wairoa River (likely near modern-day Clevedon). These were
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