Understanding the Dynamic Movement of New Zealand's North and South Islands
New Zealand's North and South Islands are geologically fascinating due to their movement on the boundary of the Pacific and Australian tectonic plates. These tectonic plates are in constant motion, and significant seismic events can affect the relative positions of these islands. This article delves into why these movements occur and the implications of such phenomena on the geography of New Zealand.
Tectonic Forces and Earthquakes
The earthquakes that New Zealand experiences are primary indicators of the shifting movement of the earth's crust. Despite being situated on the same plate, the islands are subject to shifts akin to continental plates, leading to changes in the heights and shapes of mountain ranges. For example, the Napier foreshore experienced a distinct change in 1942 when land rose from below sea level, indicating the dynamic nature of these geological processes.
Movement Dynamics and Implications
The movement of tectonic plates can result in localized shifts in the crust, causing the North Island to move slightly closer to the South Island. This phenomenon is part of the broader dynamics of plate tectonics and is influenced by ongoing geological activity in the region. It's important to note that while these movements can be measured, they are typically small on a human timescale. However, over longer periods, these subtle movements can lead to significant changes in the geography of the area.
Research seismologist and earthquake engineer Arun Bapat clarifies, 'While the movement is slow—measuring just a few millimeters per year—it may take several thousands, or even millions, of years for the two islands to get closer. Therefore, it is not something that immediately concerns us on a day-to-day basis.'
Considerations and Specific Movements
It is worth noting that the movement of the northwest corner of the South Island is relatively fixed to the North Island. Earthquakes along the Alpine fault move the rest of the South Island further to the southwest, which is away from the North Island. The East and South of the South Island are on the Pacific tectonic plate, while the North Island and the West and North of the South Island are on the Indo-Australian plate. The Pacific plate is trying to move north-east in relation to the Indo-Australian plate, and every so often, it succeeds in moving a bit in that direction, causing an earthquake.
The Kaikoura Earthquake in November 2016 was a notable instance, moving the South-east portion of the South Island closer to the North Island by approximately 35 cm. These seismic events, while causing immediate localized changes, contribute to the gradual, long-term movement of the islands over geological timescales.
In conclusion, the ongoing movement of New Zealand's North and South Islands is a result of the complex interactions between tectonic plates. While this movement is slow and barely noticeable on a human timescale, it plays a crucial role in shaping the geography of New Zealand over thousands and millions of years.