New Zealand is a very active seismic and volcanic region of the Pacific Ring of Fire, on the boundary of the Australian and Pacific Plates; however, there is a difference between the 2 islands: volcanoes and earthquakes on the North Island and earthquakes only on the South Island (see maps below):

Location of New Zealand volcanoes

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New Zealand Earthquake Map

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What are the tectonic features that account for the difference between the North and South Islands?

Additionally, how will this boundary develop in the future