Pictured is a mud pool located at Wai-O-Tapu on the North Island of New Zealand. The water level at this mud pool changes over time, having risen in the last two years. Layer upon layer of ash containing fragmented glass make up much of the mud pool. These layers of ash are unstable and alter to a clay after being exposed to hot water. This hot water is produced from underground magma (which in turn also provided the needed materials for a gold deposit to be formed at Martha Hill). The clay, called smectite, expands with the new heat. At this particular mud pool, the heat source is coming from the Hikurangi Trough subduction zone.
As time went on, volcanic activity lessened as the volcanic hot spot slowly migrated southeast, passing through Tauranga to be presently centred around the North Island.
Pictured are tors located on the South Island of New Zealand. Tors are towers of rock of massive size which are formed by chemical and physical weathering, usually either freeze-thaw weathering or groundwater weathering before exposure. Typically tors are meade of granite, but here they are made of limestone, which is found rarely in New Zealand. The evidence tells us the tors are indeed make of limestone: they were weathered in a scalloped surface, particles can be seen, limestone tends to weather in rounded shapes and they have a corroded appearance.
They have formed geologically fast, after the last ice age approximately 12 thousand years ago, during the most recent mountain building period.
These tors are remnants of what was once a horizontal layer. Tear-pants weathering, also called honeycomb weathering, can be seen on the tors. You can see Dan Bailey on the top right of the tor to illustrate the massive scale.
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