Reporoa Caldera facts for kids

Quick facts for kids Reporoa Caldera
Reporoa Caldera Location in North Island
Highest point
Elevation	592 m (1,942 ft)
Geography
Location	Taupo Volcanic Zone, New Zealand
Geology
Mountain type	Caldera
Last eruption	1180 (?)

The Reporoa Caldera is a huge, bowl-shaped hole in the ground in New Zealand. It's about 10 kilometers (6 miles) wide and 15 kilometers (9 miles) long. This giant depression is part of the Taupo Volcanic Zone, an area famous for its volcanoes.

The caldera was created around 230,000 years ago. A massive volcanic eruption caused the ground to collapse inwards. This eruption was so big it shot out about 100 cubic kilometers of ash and rock! This material formed a thick layer called the Kaingaroa Ignimbrite.

Inside the caldera, you can find three rhyolitic lava domes. These are named Deer Hill, Kairuru, and Pukekahu. The caldera is also linked to three areas where hot water and steam come out of the ground. These are called geothermal fields. The active Reporoa geothermal field is right inside the caldera. The Waiotapu geothermal area is just north of the caldera's edge. The Broadlands thermal area is to the south. The Waikato River, New Zealand's longest river, flows through the southern part of the caldera.

What is a Caldera?

A caldera is a large, bowl-shaped hollow. It forms when the ground collapses after a huge volcanic eruption. When a volcano erupts with great force, it empties the magma chamber beneath it. Without support, the ground above the chamber sinks, creating a caldera.

How Reporoa Caldera Formed

The Reporoa Caldera formed during a massive eruption. This event happened about 230,000 years ago. The eruption was so powerful it released a huge amount of volcanic material. This material is called tephra, which includes ash and rock fragments. The ground then collapsed, forming the caldera we see today.

Geothermal Activity

The Reporoa Caldera area is very active underground. This is because it's part of the Taupo Volcanic Zone. Hot magma deep below the surface heats water. This hot water and steam then rise to the surface.

Geothermal Fields

There are three main geothermal fields linked to the Reporoa Caldera.

• The Reporoa geothermal field is located right inside the caldera. It shows signs of active heat.
• The Waiotapu geothermal area is just north of the caldera. It is famous for its colorful hot springs and geysers.
• The Broadlands thermal area is found to the south. These areas are important for studying Earth's heat.

Hydrothermal Explosions

Sometimes, sudden bursts of steam and hot water can happen. These are called hydrothermal explosions. They occur when superheated water underground turns into steam very quickly. This causes a sudden release of pressure.

Past Explosions

In April 2005, a large hydrothermal explosion happened. It occurred in a cow paddock within the Reporoa Caldera. This explosion created a new crater about 50 meters (164 feet) wide. A similar big explosion happened in the same area in 1948. Smaller explosions have also occurred in the years between these larger events. These explosions show that the area is still geologically active.