A 1950 eruption covered some 100 square kilometers. Another volcano, Kiluea, is usually active, but lava actually flows from it about once in every seven years. A 1960 flow from Kiluea covered 10 square kilometers, adding some 260 hectares to the island's size. Hawaii is a state of rugged slopes and abrupt changes in elevation. This is the result of the erosion of the volcanic surfaces by moving water.
Sea cliffs cut by waves form a spectacular edge to parts of the islands.
Some small streams on the northeast side of the Big Island drop over such cliffs directly into the sea. Stream erosion has heavily dissected many of the lava surfaces. Canyons lace many of the domes. The floor of Waimea Canyon, on Kauai, is more than 800 meters below the surface of the surrounding land. Waterfalls several hundred meters high are common on the islands.