Maui Nui
Maui Nui ( Maui Hawaiian Large ) was an island, which included the land mass of the present-day Hawaiian islands of Maui, Molokai, Lanai, Kahoolawe and Penguin Bank. The island was formed about two million years ago by the activity of seven shield volcanoes that contributed to the formation of the massif. The volcanoes today make all their own islands, with the exception of Penguin Bank, which plummeted from 500 m above 1600 m and is now considered coral reef below sea level.
- 4.1 Literature
- 4.2 External links
- 4.3 Notes and references
History
Formation
→ See also: Hawaii- Emperor chain of islands
The Hawaiian Islands formed by volcanism, which is caused by a hot spot over which the Pacific Plate is moving northwest of time. This chain could be of shield volcanoes that emit large masses of basaltic lava and so grow the islands. Here, on the one hand the land mass itself is raised to others about it forms a shield of cooled lava that it increases further. Removes the island so raised by the plate motion from the hot spot, the growth decreases slowly before the island then drops again. This happens because of the volcanic activity is completed and the weight of the land mass on the thin oceanic plate can not counteract. In addition, borne mainly by the erosion by wind and landslides to the fact that the volcanic rock of the islands is sinking in the sea.
In the case of Maui Nui seven volcanoes were responsible for the emergence of the island: Penguin Bank, West Molokai, East Molokai, Lanai, West Maui, Haleakala and Kahoolawe. Here, the age of the volcanoes of the north-west to south-east takes off steadily and between 2.2 ( Penguin Bank) and 1.2 million years ago ( Kahoolawe, and Haleakala ). This Penguin Bank was during its creation is ultimately linked to the island of Oahu in the northwest, and the same is probably true for West Molokai. These compounds consisted only of front 2.2 to 1.9 million years ago. This " Oahu Nui " reached a maximum extension of 7,000 km ².
Development and demise
Prior to about 1.8 million years ago the connection was finally definitively broken after Oahu, Molokai simultaneously East had completed its growth, which one can speak of a specific island of Maui Nui for the first time. West Maui and Lanai were at that time in the early stages of plate formation, East Molokai had lost a portion of its surface by a landslide, but the surface Maui Nui was already at that time about 5,000 km ², East Molokai was at 3,000 m the highest peak. While Lanai, West Maui, Haleakala and Kahoolawe continued to grow, the older northwestern volcanoes fell off again. With the end of the growth of Haleakala before 1.2 million years Maui Nui reached its greatest extent, around 14,000 km ²; about one and a half times the size of Hawaii Island today.
As a result, the island area decreased greatly at the same time, the islands separated from each other. However, the size was subject to strong fluctuations, which are caused by the growth and melting of global glacier mass. Already a million years ago, the connection between Penguin Bank and the rest of the island broke off the first time; the area between East and West Maui Molokai was flooded around 700,000 years ago, but they remained connected to Lanai. 600,000 years ago, the connection broke out between East Molokai and Lanai, but was temporarily new again; same thing happened 200,000 years later with West Maui. The isthmus between the eastern and the western part of Maui, however, was apparently never interrupted, since it lies too high above sea level and only drops slowly. However, he is now 70 m above sea level as low as never before. The saddle - Haleakala Kahoolawe disappeared about 200,000 years ago. Although he appeared possibly 150,000 years ago again, during the last glacial highs around 20,000 years ago, however, he was already sunk too deep. At this time the total area of the islands was about 5,900 km ², about double the present area. Over the past 1.2 million years, the four islands of Maui Nui were connected for 75 % of the time.
Topography, ecology and climate
Maui Nui differed from today's Hawaii topographically by large heterogeneity: 77 % of the area was below 1000 m, thereby indicating strong contrasts of the few altitudes 2000-3700 m. This probably resulted in a different climate than in Hawaii: Because of the large proportion of lowlands, there were higher temperatures, rain forest could train out irregularly due to the diminished degree slopes to the coast, as the rain did not follow a specific pattern. However, Maui Nui should have possessed the necessary size to cause orographic rainfall.
For the biogeography of the Hawaiian Islands Maui Nui's development played an important role. First, the land bridges allowed to Oahu the propagation of plants and flightless birds by Penguin Bank and West Molokai. From there they spread out to the whole of Maui Nui, finally to be isolated on the islands again and form new species. Thus formed solely the genus Tetramolopium from the Asteraceae family of eleven species on Maui Nui, while the extinct Maui Nui ibises ( Apteribis ) lost their ability to fly here. Even Maui Nui was closer to the other Hawaiian islands as today, the distance to Hawaii was 500,000 years ago, just 15 km (now 50 km); a circumstance that enabled the colonization of Hawaii. Maui Nui had thus played a key role for the high biodiversity of the surrounding islands. At the same time also show the former affiliated islands have a higher biodiversity than the rest of the archipelago.
Research
The thesis of a large contiguous land mass at the site of today's islands was first postulated in 1942 by Harold Stearns and Gordon Macdonald, but they could not make any statements to age or duration of this formation. It was not until the 1970s, this hypothesis could be proven as bathymetric studies showed an undersea massif to Maui around. After they had found that parts of this massif were dropped in the past up to 2000 m, the mid-1990s the theory was formulated, Maui Nui was only connected to Oahu before it as an independent island reached an area of over 10,000 km ² and finally disintegrated by rising sea levels and the reduction of volcanoes in individual islands. This was finally confirmed by paleoclimatic and geological analyzes 2004.