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什么构造机制导致新西兰南北岛地质不同?

新西兰是一个非常活跃的地震和火山地区的太平洋火环”断裂带,在澳大利亚和太平洋板块的边界;然而,是有区别的两个岛屿:朝鲜岛上的火山和地震和地震只在南岛(见下面的地图):

新西兰火山的位置

在这里输入图像描述

(图片来源)

新西兰地震地图

在这里输入图像描述

(图片来源)

是什么构造特性,占北部和南部岛屿的区别?

此外,这个边界发展在未来将如何(从地质学角度讲)?

回答

新西兰坐落在一个斜会聚板块边界,太平洋和澳大利亚板块相遇的地方。两个板块之间的边界是你的第二个图所示为灰色线,与东部和太平洋板块向西澳大利亚板块。的相对运动,我们可以认为澳大利亚板块是静止和太平洋板块西西南方向的运动。太平洋板块的角度进入新西兰的澳大利亚板块沿长度变化——这是什么导致构造样式的差异,因此不同的火山和地震(运动)出现南北之间的岛屿。从北到南角变化由于:1。太平洋板块的顺时针旋转,和2。太平洋和澳大利亚板块会议以不同的角度。如果这个边界是直和太平洋板块移动正交,然后只会俯冲,太平洋板块的密度比澳大利亚。相反,如果太平洋板块平行移动到澳大利亚板块就没有俯冲。沿着新西兰这两个包(和之间的差异)是观察到,不仅是板块边界稍弯曲在新西兰的长度,但太平洋板块的运动顺时针旋转的一个组成部分。 [Lamb (2011)][1] shows that there has been 70-90 degrees of clockwise rotation of the boundary/margin over the last 20 million years, and it is still occuring today. The differing angles of intersection between Pacific and Australia plate along the length of NZ cause differences in tectonic style, which give rise to differences in volcanism and earthquake occurance and motion. [The figure in this section of the Geology of New Zealand Wikipedia page][2] shows the variations of displacement vector (direction and magnitude of motion) along the length of New Zealand. Notice how the vectors are more orthogonal to the plate boundary in the North Island and become more acute in the South Island. Subduction occurs in the North Island because the Pacific Plate moves rougly orthogonal to the boundary with the Australian Plate and is denser than than the crust around New Zealand; the Pacific Plate is composed mainly of basalt, while New Zealand is an amalgamation of different sedimentary and volcanic rocks. As the Pacific Plate is subducted is bends and breaks, causing earthquakes. It also melts, causing volcanoes. Notice how the depth of earthquakes in the North Island gets deeper to the west - this is due to the continued westward movement of the Pacific Plate even as it subducts under the Australia Plate. Over most of the South Island the Pacific Plate moves roughly parallel to the boundary of the Australia Plate. The Southern Alps are caused by slight obduction (up and over movement) of the Pacific Plate over the Australia Plate. To the south of the South Island the polarity of subduction is reversed, with the Australian Plate being subducted beneath the Pacific Plate (e.g. [Randall, 2007][3]). This post is a huge simplification of the tectonics of NZ. The geology of this continental fragment is very complicated, but also very interesting! Have a look at [this video][4] to see how the plate boundary has changed over time. [1]: http://www.sciencedirect.com/science/article/pii/S0040195111002204 [2]: http://en.wikipedia.org/wiki/Geology_of_New_Zealand#Astride_a_plate_boundary [3]: ftp://ftp.earth.ox.ac.uk/pub/karenr/thesis.pdf [4]: http://www.youtube.com/watch?v=E6Nyr78Mqyg

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