Hawaii
Beaches
Mahaiula Beach and Kawili Point, Kona Coast
Black Sand at Makolea Beach near Ka Lae, Hawai'i
Hawaii is made of lava. As soon as volcanic rocks are formed, they begin the erosion process. Lava that flows to the sea is ground into sand by the ocean surf... but black sand is temporary! It will be eroded into very tiny particles which will be carried away by the surf.
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at Kalapana lava delta new black sand has formed only a few meters from the molten lava |
Makolea Beach on the 1801 Hualalai lava flow near Kona |
surf at Laupahoehoe shows why sand is rapidly carried away |
Black and White at Ka'elehuluhulu Beach near Kona, Hawai'i
As storms wash away the black lava sand, pieces of coral from the growing reef offshore are broken by storms and thrown onto the beach.
The coral rock is eroded into sand. It is more resistant to erosion than lava, so it it survives longer on the beach. After a few centuries it begins to predominate. As time goes on, the beach will be whiter and whiter.
a littoral cone forms green sand at Mahana Bay near Ka Lae
At Mahana Bay a volcano erupted at the very edge of the sea. The cone has been half-destroyed and is being slowly washed away. One layer of lava contains an unusually high content of olivine - a green mineral. The Olivine is harder and heavier than other components, so as other lava components are washed away, the olivine has become concentrated to about 60 - 80% of the sand.
So many visitors carry green sand away from this beach that it may actually be destroyed shovelful by shovelful!
More beaches...
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Beach litter - all the beaches show the impact of non-biodegradable rope and floats from fishing. There are massive piles of tons of twisted fiber |
Makelawena Beach, Kona |
Lovely, accessible and enjoyable. Kona Coast |
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Waikiki Beach and hotels looking back from Diamond Head |
Waikiki Beach at dawn when things are relatively quiet, but definitely not deserted. Diamond Head in the background
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The coast is not all beaches -- much is surf or dramatic cliffs as in this photo at Ka Lae |
Not exactly a beach.
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the lava "bench" is a temporary beach where lava sand recently formed from the nearby lava flow is piled loosely by the surf. It is very unstable and can collapse or landslide at any moment.
"Don't go on the bench" our geologist told us.
for more, see volcano