New Zealand's landscape

New Zealand has over 15,000km of of coastline. The sand in the North Island is dark with it being comprised chiefly of iron. The North region of the South island has more beautiful sandy beaches but the coastlines around the rest of the South Island tend to be rugged and wilder.
Over millions of years, alluvial deposits (eroded from the mountains by rivers) formed the vast Canterbury Plain in the South Island and a number of smaller plains in the North. These alluvial plains contains some of New Zealand’s most fertile and productive farmland.
The North Volcanic Plateu has extensive ignibrite (pumice rich pyroclastic flow) it extends from Rotorua to Mt. Ruapehu. In the North, the land is very fertile, whereas in the South the land is forested. In the east the land is barrent and the alpine climate is harsh and bare.
The compression and collision of the palte edges in the North Island form the Biburingi Trench. 75% of New Zealand’s surface consists of mountains and hills. The subduction boundary causes the Pacific plate to subduct underneath the Australian plate which contains the North Island. To the South of the island, the situation is reversed. In the North Island, this causes the Rimultaku range across the north island. This process also causes intense volcanic activity that the North Island is famous for. In the South Island, the mountain building process (smashing of the two plates) form the Southern Alps.