If you're an amateur geologist, the chance to watch a mountain range growing is not to be missed. North from Ashhurst, and clearly visible from the road, the Pohangina Anticline runs alongside the Tararua and Ruahine Ranges, which both began life as anticlines about half a million years ago. Rising at a rate of at least one millimetre a year, Pohangina is growing rapidly in geological terms.An anticline is essentially a convex fold of rock - blocks of deep, old, hard rock are slowly bending softer overlying rocks upwards. Anticlines aren't common, and not usually visible from public roads. Another interesting natural phenomenon is the nearby Manawatu Gorge, a textbook example of what happens when a mountain range rises across a river. The Manawatu River is one of the few in the world flowing east to west through a main divide.