New Zealand volcanoes

New Zealand has volcanoes stretching from the Bay of Islands down to Otago. Many of our volcanoes are extinct (no longer active), some are dormant (not active but capable of becoming active) and some are active – meaning they still erupt from time to time.

There have been some famous volcanic eruptions in our country’s history:

• One of the world’s largest explosions in the last 5,000 years happened when volcanic vents in the Taupō region erupted. The huge crater that was left filled with water and formed Lake Taupō.
• Tarawera, a volcano near Rotorua, erupted in 1886. It is thought that 120 people died.
• Ruapehu is our largest active volcano. It erupted in 1995 and 1996 and again about 10 years later.
• Whakaari/White Island, in the Bay of Plenty, is our most active volcano. It regularly gives off steam and gases. In December 2019 it erupted killing a number of people.

New Zealand has different types of volcanoes

When we think of volcanoes, we often picture volcanoes like Mt Taranaki or Mt Ruapehu. They look like an upside down ice cream cone with smoke coming from the peak. This type of volcano is called a cone volcano. Thick lava flows down the sides of the mountain and builds up steep sides.

We have lots of volcanoes that look more like hills than cones. Sometimes, extinct cone volcanoes – like Little Barrier Island – have their cone shape worn away by time and weather.

Magma also makes a difference to how volcanoes are formed and how they look. Sometimes, a large pool of magma lies under the Earth’s crust. Instead of coming out in a single vent, it comes out at lots of different points, making a number of small volcanoes in a small area. This is called a volcanic field. Auckland and Whāngārei both have volcanic fields. In the Auckland area, there are nearly 50 small volcanoes.

Shield volcanoes are formed by runny magma that flows quickly from the vent. This kind of volcano is kind of like water coming out of a sprinkler. As water erupts from the sprinkler, it quickly spreads to form a thin layer on the ground. The lava from a shield volcano spreads over a wide area and forms gently sloped sides. Banks Peninsula in Canterbury is the remnant of two large shield volcanoes. Rangitoto is an example of a small shield volcano, with small scoria cones on top.

There is another type of volcano that doesn’t look like a cone. Caldera volcanoes are really violent. They throw ash and rock all around. Sometimes, rocks and gases move from these volcanoes at speeds of over 1000 km per hour! After such a large eruption, the volcano collapses into a big hole. Lake Rotorua and Lake Taupō were formed this way.

The Pacific Ring of Fire

New Zealand is part of the Ring of Fire that circles the Pacific Ocean. The Ring of Fire follows the edge of the Pacific tectonic plate. About 90% of the world’s earthquakes and 75% of the world’s active and dormant volcanoes are on this ring.