Here you can almost see Mt. Ngauruhoe, the youngest of the three volcanoes in the park which formed a mere 2500 y.a. If you could see it better you may recognize it as Mt Doom from the Lord of the Rings movie. Mt. Ngauruhoe last erupted in 1975.
Red Crater was in my opinion the most aesthetically interesting feature of the hike. It is a scoria cone replete with iron ore, hence the color, that was formed 3000 y.a. The most recent activity in this crater was between 1855 & 1890.
This feature is a dike that formed underground and was then exposed as the crater eroded away.
These are known as the Emerald Lakes.
This is a basaltic lava flow.
In this photo you can see just how much traffic this trail gets. Although not immediately obvious, the ground behind Kriss is vertical. This was a trench dug by many years of hikers using the same trail.