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| Zealandia's Full Underwater Expanse (google.com/images) |
The land masses we know today as the islands of New Zealand happen to be at the highest elevation of a greater microcontinent known as Zealandia. Once a part of the super continent Gondwana, Zealandia separated over 70 million years ago as a result of shifting circulations in the earths asthenosphere. Under the supercontinent, new flows of molten rock moved outward and pulled the land apart. The lowland rift between Zealandia and its former motherland filled with ocean, forming the Tasman Sea. After millions of years of sea floor spreading as well as the cooling of the continent, Zealandia was nearly entirely submerged beneath the waves.
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| New Zealand's Tectonic Turmoil (google.com/images) |
Picturesque enough to star in movies such as The Lord of the Rings and The Chronicles of Narnia, these islands also find themselves atop two tectonic plates, and three different kinds of plate boundaries. The North Island is the more actively volcanic of the two due to the subduction zone off it's east coast where the Pacific Plate sinks underneath the Australian Plate. The grinding and heating between the two plates has resulted in the Taupo Volcanic Zone which includes the largest active volcano Mt. Ruapehu among many other composite or stratovolcanoes.
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| A Calm Mt. Ruapehu (theencyclopediaofnewzealand.com) |
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| Mt Ruapehu 1995 Eruption (tera.gov) |
The major eruption in 1995 resulted in fast moving lahars, a combination of mud and volcanic ash that mixed with the emptied crater lake water and melted snow. Although the ash affected some livestock and a nearby hydro electric power plant, there were no casualties reported. Without a dense population nearby, the 1945 eruption also had little direct impact on New Zealanders. However the eruption blocked off the lower drainage point of the lake with tephra or pyroclastic material. After the lake had refilled by 1953 the weaker tephra broke free, releasing a devastating lahar that compromised a railway bridge causing 151 deaths known as the Tangiwai disaster.
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| Wreckage From The Tangiwai Disaster (google.com/images) |
Kevin,
ReplyDeleteYou did a great job explaining the way the islands of New Zealand formed from the greater microcontinent. Explaining the circulation of the asthenosphere and the subsequent flows of magma rock really help the reader to visualize what caused the separation of land masses. I also think it's great the way your writing flows from one topic to another. Explaining the tectonic activity that formed the volcanoes and following up with case studies of volcanic activity was a great way to exhibit the way that those geographical landforms can affect the people of New Zealand.
-Melissa Skinas
Thank you for explaining how New Zealand was formed. Considering the volcanic activity, I would have thought it formed much like Hawai'i, I would have never guessed that it was almost the oppisite. You did a wonderful job explaining the tectonic properties of New Zealand. No wonder there's so much activity there!
ReplyDelete-Tiffany Dubois