During the ice age, large parts of New Zealand were covered in glaciers and ice caps. As the glaciers retreated, they cut through the rocks, forming the valleys, deep lakes, and fjords we see today. The high valleys and incessant rainfall have also made the region abundant in waterfalls. Fiordland also has some of the oldest rocks in New Zealand, especially the hard crystalline metamorphic rocks. As the area is close to the alpine fault where two of Earth’s plates meet, Fiordland has large deposits of sandstone, mudstone, and limestone.