The "Three Sisters" at sunset, Tongaporutu, North Taranaki
The "Three Sisters", a collection of rock stacks immediately south of the Tongaporutu River mouth, are the last-standing remnants of older sea caves that have since been breached as the cliffs were eroded landwards by the sea. A fourth "Sister" previously stood alongside them, before finally surrendering to a powerful storm in the early part of the 20th century.
The process of creation and eventual erosion and elimination of these stacks is ongoing. The cliffs along this coast feature numerous arches and caves, each of which is a potential stack, or Sister in the making. With every tide, these arches and caves are eroded out just a little bit more, while those stacks that already stand separate from the cliffs are slowly but surely ground down and washed away. While these stacks seem strong and everlasting, they will be ultimately claimed by the relentless action of the sea, to be replaced by new ones as the cliffs continue to erode.
The temporary nature of these landforms is well illustrated here: the smallest "Sister" in this photograph was almost completely destroyed by a storm in October 2003 and is now little more than a rounded stump, barely a quarter of its former height.