Unveiling New Zealand's Tectonic Tale

The science beneath our feet

Theory of Plate Tectonics

The Inner Core

The Earth's inner core is a solid, dense sphere composed primarily of iron and nickel.

The Outer Core

Surrounding the solid inner core is the fluid outer core composed of molten iron and nickel

The Lower Mantle

The lower mantle is a highly viscous region of Earth's interior, composed mainly of silicate minerals.

Both mantles are around 2,900 kilometres thick.

The Upper Mantle

The upper mantle is a layer of semi-solid rock beneath Earth's crust, extending to about 660 kilometers deep

The Crust

Earth's crust is the outermost solid layer, composed of a variety of rocks and minerals, forming the continents and ocean floors, and is the thinnest of Earth's layers.

Tectonic plates

Currents within the mantle, along with the force of gravity has lead to the fracturing of the Earth's crust and upper mantle

Divergent Boundary

At divergent plate boundaries two plates move apart from each other

Convergent Boundary

At convergent plate boundaries two plates collide and one is pushed beneath the other resulting in a subduction zone, and the overriding plate forms mountain ranges

Transform Boundary

At transform plate boundaries two plates grind past each other sideways

Earthquakes

As these plate shift stress accumulates, and is occasionally released in the form of an earthquake.

some plate boundaries have more active faults than others, like the Pacific Ring of Fire

Pacific Ring of Fire

The Ring of Fire is a horseshoe-shaped zone in the Pacific Ocean basin, characterized by frequent earthquakes and numerous active volcanoes.

It spans approximately 40,000 kilometres and includes regions such as the coasts of South America, North America, Japan, and New Zealand. This area is a result of tectonic plate boundaries and movements, making it one of the most geologically active regions on Earth.

Each green light represents a earthquake along the Pacific Ring of Fire

Hundreds of thousands of earthquakes occur all around the world every year.

As more and more occur a pattern starts to emerge, tracing the edge of the Pacific tectonic plates.

The Pacific Ring of Fire becomes clearer with every earthquake that occurs, it follows the same outline as the Pacific Ocean

The Pacific Ring of Fire is the most active tectonic region in the world!

90% of the world's earthquakes and 80% of the tsunamis occur here

In the southwestern corner of the Pacific Ring of Fire lies New Zealand, situated at the boundary of the Australian and Pacific plates. This positioning is the reason for the frequent earthquakes experienced in the region.

Each year, over 20,000 earthquakes are recorded in New Zealand,

Earthquakes

Earthquakes are triggered by the buildup of stress along fault lines where plate boundaries meet. They are measured by their magnitude on the Richter scale, ranging from 0-10 with 10 being the strongest. the scale indicates how much energy was released with each magnitude level being 10x stronger than the previous.

Click on any of the green points on the map to learn more about the various earthquake magnitudes around New Zealand.

New Zealand earthquakes from 1900-2024

Fault line

A fault is a fracture in a rock where significant displacement has occurred due to movement of the rocks either side of the fracture. The largest faults on Earths crust result from plate tectonics forming boundaries between the plates.

New Zealand sits on top of one of these plate boundaries where the Australian plate meets the Pacific plate at a fault. this has created an array of unique topography around the country, from deep trenches to tall mountains the fault line is very prominent throughout New Zealand.

Kermadec Trench

Spanning over 1,000km, the Kermedec trench is where the Oceanic crust of the Pacific plate subducts under the overriding Oceanic crust of the Australian plate at a convergent boundary, leaving a deep valley in the seafloor that can reach depths of up to 10km, making it the 5th deepest trench in the world!

Hikurangi Trough

Being much shallower than the trench north of it, with a maximum depth of 3,700 meters the Hikurangi trough is a subduction zone at a convergent boundary, where the Oceanic crust of the Pacific plate is subducting under the continental crust of the Australian plate.

Alpine Fault

Stretching 600km long, the Alpine Fault runs along the entire length of the South Island. over the last 12 million years, earthquakes have caused uplift creating The Southern Alps. However it is a transform boundary with the two plates grinding alongside each other during major large magnitude earthquakes.

Southern Alps in the South Island

The last large major earthquake that occurred on the Alpine Fault was in 1717AD with a magnitude of 8.1, the Fault is still active though moving roughly 37-40mm per year

Puysegur Trench

Stretching over 800km the Puysegur Trench reaches depths of up to 6.3km.

Opposite to what is happening at the Kermadec Trench, here the Oceanic crust of the Australian plate subducts under the Oceanic crust of the Pacific plate.

This massive boundary throughout New Zealand is the reason for high levels tectonic activity, making the region highly susceptible to earthquakes. The country receives frequent seismic events, with over 20,000 earthquakes recorded annually.

Understanding and monitoring these faults is crucial for improving earthquake resilience, as they provide valuable data on seismic activity and potential hazards. By closely studying the behaviour of these fault lines, scientists can better predict the timing and magnitude of future earthquakes, enabling the development of more accurate early warning systems.

In a geologically active area like New Zealand, where the risk of seismic events is high, these efforts are indispensable, the commitment to understanding and monitoring fault lines is a key component of a comprehensive strategy to mitigate the impacts of earthquakes in the region.

Southern Alps in the South Island