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The view over the plains from Tirohanga

Why are there hills and plains to see here?

Think for a moment about why some places are flat and some are hilly. What creates the hills and why are some hills higher than others.

The form of landscape here is created by faults in the earths crust where one part moves relative to another in an earthquake. The far hills are being pushed up by movement on the Henley fault which runs along the bottom of the hill. The  hill you are standing on was thrust up by earthquakes on the Titiri fault which runs more or less along the bottom of the hill. Movement is very slow with an major earthquake only every 3-6000 years. Rainfall slows weathers and washes away the rock that is thrust up but not all rocks are created equal. Some are much harder than other. Looking over to Saddle Hill (named by Captain Cook), we see rocks that are the remains of a volcano. Saddle hill was once a conduit for molten lava spilling out of volcano 13 million years ago. The Dunedin volcano is now heavily eroded away but lava tubes like Mt Cargill, Harbour Cone and Saddle Hill stand out because they are much harder. The rock they are made of is called Phonolite (a type of basalt) by geologists and is the "Bluestone" used in making the old university building and the railway station.