The Taupo Volcano erupts rhyolite, a viscous magma, with a high silica content.
Taupo began erupting about 300,000 years ago, but the main eruptions that still affect the surrounding landscape are the Oruanui eruption, about 26,500 years ago, which is responsible for the shape of the modern caldera, and the Hatepe eruption, about 1,800 years ago.
However, there have been many more eruptions, with major ones every thousand years or so (see timeline of last 10,000 years of eruptions).
Valleys were filled with ignimbrite, evening out the shape of the land. Loose pumice and ash deposits formed lahars down all the main rivers.
The eruption further expanded the lake, which had formed after the much larger Oruanui eruption.
While Taupo has been active for 300,000 years, explosive eruptions became more common 65,000 years ago.