The coastlines are rocky and predominantly barren with fjords. The Norwegian mountains plunge into the sea creating deep fjords and archipelagos. Hanging valleys are common along glaciated fjords and U-shaped valleys. They inhabit fjords, bays, estuaries and harbours, hence their name. These appeared in central locations along Scandinavia's coasts near natural harbors or fjords. The people extended their culture along the fjords and coastlines in the area. The rugged coastline is broken by huge fjords and thousands of islands. Nordland has a rugged coastline, with many fjords. The plant communities at Kenai Fjords are shaped by glacial retreat. Small waterfalls within these fjords are also used as freshwater resources. Along the coast are deep, narrow fjords. In 2000, some coral reefs were discovered along the bottoms of the Norwegian fjords. There are several large fjords that stretch quite far inland. Viking settlements were established in the sheltered fjords of the southern and western coast. The Norse established settlements along Greenland's fjords.