Today we had to take a boat ride to see the geyser activity.
Arrived at Waimangu as they were opening. The area takes its name from the ex-geyser. It's a several mile long hike down a series of volcanic explosion craters from the 1886 Tarawera eruptions to the shore of Lake Rotomahana. It was raining off an on for the first few hours, and we had two hours to get to the lakeshore for our boat ride. Fortunately, there is an infrequent shuttle bus, and we were able to take advantge of it several times.
At first we encountered several deep craters with weak thermal activity whose bottoms had pools mostly filled by rainwater.
The site of Waimangu Geyser is now a relatively flat area at the bottom of a crater with a stream around one side and lots of fumaroles and sputs along the stream banks. The first time we were there we didn't realize what it was.
From there the trail follows the stream, which has cut a deep gully in places, and the banks were lined with more activity. Some of the springs have already built up nice rims around them, and there could have been a geyser or two among all the sputs we saw there.
Just downstream from a bridge, there's a perpetual spouter putting up a thin, continuous stream of water to a height of two to three meters. Just before it was a mostly dry, large runoff channel. We climbed the steps the were beside it to the overlook for Inferno Crater.
Inferno Crater is a "crypto-geyser". It doesn't throw water into the air, but shows all the other behaviors associated with geysers-- primarily periodic discharge of water. In this case, the interval runs from days to weeks. The water level varies from heavy overflow to down several meters, We were there when it was low, but this was good, because that seems to be when it has the best color. In the morning, it looked a bit gray, thanks to the clouds and rain. But when we visited it a second time, in the sunny afternoon, it was a deep, bright blue.
We also visited Warbrick Terrace where there's a large apron of runoff punctuated by numerous small sputs.
The boatride was well worth it. The activity of the geyser we saw, "Pink Terrace Geyser", is dependent on the lake level. When we were there, the level was high. So high that some of the walkway by the shore was closed due to flooding. The higher the lake, the more vigorous the activity. What we saw lasted about 90 seconds or so and reached a height of around eight to ten meters. The boat operator said that the intervals were around seven minutes. Also along the shore were a number of other spouters, and some features drowned by the high lake levels.
Turns out we missed the Iodine Spring, which sometimes acts as a geyser. It's along the bus road, while we went by on the trail on the other side of the stream. From our vantage point, we did see what looked like another perpetual spouter over there.