Along the sea cliffs that surround the Island of Hawai’i, arches and sea stacks are formed where wild waves and tides exploit minute differences in the hardness of various layers of lava flow and airfall material, making strange, gravity-defying natural sculptures. Although common, there are few places where these arches and stacks are easily viewable–one such place is the Holei Sea Arch, which is currently directly seaward of the end of the Chain of Craters Road.

At Holei Sea Arch the cliffs are 80 to 90 feet high, but many waves still spray and wash over them, so use caution when approaching and photographing the arch. Notice along the lower cliffs in the area toward the eruption viewing platform, the several large boulders which have been dropped by giant, angry waves crashing over the sea cliffs. Imagine the power of a wave that would have enough force to deposit a several-ton boulder on a cliff 30-60 feet about the surface of the ocean.
http://lovingthebigisland.wordpress.com/2010/03/11/exploring-hawaii-volcanoes-national-park-holei-sea-arch/

--- http://lovingthebigisland.wordpress.com/2010/03/11/exploring-hawaii-volcanoes-national-park-holei-sea-arch/