Geo-post Cards- Colette Hyatt

Lady Knox Geyser

This picture shows a geyser found at the Wai-O-Tapu area in the Taupo Volcanic zone on the North Island of New Zealand. The geyser was named after Lady Constance Knox in May of 1903. It has two water chambers with one being lower and hot and the other being higher and cold. The lower chamber is heated by volcanic activity. This geyser was discovered by prisoners who were clearing bush in the area. They were using the hot water from the geyser to wash their clothes. They discovered that the washing soap could trigger an eruption. This occurs because the soap breaks the surface tension between the two layers and this allows the colder water to mix with the hotter. This releases pressure and causes the eruption. The eruptions can produce a jet of water up to 20 m and it can last for over an hour. Presently, 300g of biodegradeable soap is added at 10:30 am every day to create an eruption for visiting tourists. The geyser did not always look like it does in the picture above. The prisoners who discovered this geyser piled the rocks around the base. This was done to make a more intense and localized eruption. The eruptions have given the geyser the white silica covered cone-shaped appearance. This geyser is similar to Old Faithful found in Yellowstone Park of the United States.

Huka Falls

These falls are found on Waikato River that drains from Lake Taupo on the North Island of New Zealand. The Waikato River is the most highly developed river for electricity generation in New Zealand. This river supplies eight hydro stations and supplies cooling for two geothermal stations and one thermal station. These eleven stations produce 65 % of North Island’s power generation. Huka Falls have an average flow of 5,000 cubic feet per second. At the top of the Huka Falls there is a set of small waterfalls that drop over 8 m. and the final stage of these falls is an 11 m drop. In geological time waterfalls do not occur for long. Waterfalls show a change in the direction of a river system. The Huka Falls were created when an ancient lake drained Waikato River and eroded through soft mudstone and pumice. This occurred until it struck a layer hardened by silica. Over time the river then cut a deep narrow channel into the hard layer until it reached a soft underlying layer that collapsed. This created the steep-sided basin of the Falls.