East Coast and the Hikurangi tectonic plate boundary
Here on the East Coast, we are close to the Hikurangi tectonic plate boundary which lies just off the coast. This is the boundary between the Australian plate and the Pacific plate.
The Hikurangi tectonic plate boundary is a convergent boundary. This means that the Australian and Pacific plates are pushing against each other. There are two kinds of plates – oceanic and continental plates. When oceanic and continental plates meet, the denser oceanic plate moves under the less dense continental plate. The Australian plate is a continental plate and the Pacific plate is an oceanic plate. At this boundary, the Pacific plate is slowly moving under the Australian plate. This process is called subduction and creates a deep oceanic trench.
As the Pacific plate moves under the Australian plate it melts and forms molten or partly molten rock below the Earth’s surface called magma. Magma builds up and creates pressure under the earth’s surface and when this pressure is released it causes earthquakes, tsunami, and volcanic eruptions.