Mount Tarawera

This location is at the heart of the extremely violent eruption that occurred on June 10th 1886. It killed about 120 people and covered the surrounding areas with metres thick of volcanic debris. The eruption occurred along a 17km line of craters resulting in the excavation of a spectacular rift across the mountain.
Mount Tarawera has lavas and explosive deposits from five eruptions. The first four are silicic (silica rich rhyolite magma) and were erupted between about 21,800 and 700 years ago, whereas the most recent is basaltic - a very different type of volcanic rock. The silicic eruptions are named Okareka, Rerewhakaaitu, Waiohau and Kaharoa from oldest to youngest.
The basalt erupted in the 1886 Tarawera eruption was very unusual for a rhyolite caldera complex. Basalt is derived from great depths and is the sort of rock more typical of Auckland's Volcanic Field It rarely makes it to the surface in the Taupo-Tarawera area.
The 1886 eruption was unusually explosive for basalt and the fissure you are peering into was excavated in an eruption that lasted only about 6 hours.
The summit is made of four lava domes of the Kaharoa eruption, Wahanga, Ruawahia, Crater and Tarawera Domes from east to west. The largest fissure that the access road brings you to at first is cut through Ruawahia Dome. The fissure is mostly filled with fragments of pumice and scoria from the explosive phases of eruptions. You can see bits of the dome sticking through the talus as low bluffs. The vertical darker band at the southwest end of that fissure is the remnant of the basalt dike that fed the 1886 fissure eruption.

Can you tell the difference between rhyolite and basalt in Ruawahia Crater? Basalt has a lot more iron and magnesium in it so it's a different colour. Some of the rhyolite had a lot of gas in it, but the rest did not - especially the material forming the dome rock bluffs that the fissure cuts into. Looking at the crater wall which of the two rock types are youngest? Have a look around you on the ground. Can you tell which chunks of rhyolite were gas rich?
How is Lake Rotomahana related to the mountain? The 1886 eruption also went through there as far as the Waimangu Valley. What would have been different there in terms of the eruption process compared to on the mountain?