Lower Tama Lake

BY JULIAN THOMSON (GEOLOGIST)
Accessibility: MODERATE
Lower Tama Lake, J.Thomson / GNS Science
One of several large explosion craters on Tama Saddle.
Lower Tama Lake, J.Thomson / GNS Science
There are at least six or seven large explosion craters clustered near to each other on Tama Saddle, between Ruapehu and Ngauruhoe, including craters now filled by the Upper and Lower Tama Lakes. These were active about 10,000 years ago (which is younger than the last ice age / glacial maximum) and are in the low topography away from the main mountains, which explains why they haven't been eroded by glaciers.
Lavas near this location, that form the southern rim of Lower Tama Lake, were sourced from Mt Ruapehu about 50,000 years ago. Those that make the cliffs further to the north and around Upper Tama Lake were erupted as far back as 180,000 to 250,000 years ago.
All these older lavas were already heavily eroded by the time the explosive eruptions occurred in the saddle area. The area surrounding the lakes up to about 3 km away is blanketed by volcanic (pyroclastic) material ranging in size from large blocks of andesite to ash, blasted out of the ground as the craters were formed. Taupo, Ngauruhoe, and (most recently) Ruapehu, have all erupted later on, adding a cover of younger ash deposits.
Tama Lakes and Tongariro, D.Townsend / GNS Science
Lower Tama Lake is accessible from different directions, but a short walk from the Northern Circuit track will take you to a good viewpoint over the lake, You can see that the lake is gradually being filled by sediment that is forming a delta on its northern side. This material is brought in via the adjacent crater by a stream flowing down to Tama Saddle from the south west. The Tama Saddle / Northern Circuit track crosses this stream valley not far to the west of the lake. How many other craters can you see from here in total? If you decide to explore the area more widely, keep a look out for circular depressions that may be old, less distinct craters. The high ground just south of the Northern Circuit track is lava that erupted from Saddle Cone, a crater on the slopes of Ruapehu about 3km to the south.
Directions/Advisory

Park in Whakapapa Village. The track starts near to the Skotel Alpine Resort.

This is a windswept and exposed alpine area. Be fully prepared for sudden changes in the weather.

All waterways including the lakes on Tongariro and his peaks Ngauruhoe and Ruapehu are sacred to local iwi, Ngāti Hikairo ki Tongariro. Kaumātua Te Ngaehe Wanikau asks visitors to the area to respect the sanctity of the maunga tapu (sacred mountains) by not touching or entering any of the waterways including the alpine lakes. Ngāti Hikairo ki Tongariro places extreme importance on their guardian role in protecting Tongariro and his peaks.

Accessibility: MODERATE

Follow the Tama Lakes / Northern Circuit track from the village towards Taranaki Falls to where it forks off to the right. Continue uphill until you reach the saddle.

Features
Volcanic
Geological Age
About 10.000 years
Zealandia Evolution Sequence
Pākihi Supergoup: 5 million years ago – present
Links
Updated weather and track information at the visitor centre in Whakapapa. http://www.doc.govt.nz/tongarirovisitorcentre