11
$\begingroup$

It's quite surprising to me that there's only one beach with black sand on Hawaii (maybe not exactly one beach, but it's only a very small fraction). The concern is, if the whole Hawaii is volcanic, therefore made of frozen lava, the sand should be black everywhere.

I suppose the true reason is that the sand on the beaches is not "made of Hawaii" or "made in Hawaii". However, I wonder how did the white sand make it there?

$\endgroup$
  • $\begingroup$ Are those white beaches natural at all, or is the sand simply shipped from the mainland for tourist purposes in modern times? I don't know how many white beaches there are there. $\endgroup$ – gerrit Aug 6 '14 at 20:16
  • $\begingroup$ @gerrit It doesn't quite look so (or they're very good at hiding it) :D en.wikipedia.org/wiki/List_of_beaches_in_Hawaii#mediaviewer/… And there's quite a handful of them. $\endgroup$ – yo' Aug 6 '14 at 20:19
  • $\begingroup$ black sand beaches are common on the south and east shores of the big island, where black basalt is prevalent/new and constantly being eroded by the ocean. Older islands don't really have much black sand and is dominated by white sands (e.g. calcified remains). Really black sand is usually like pebbles in comparison to the size of white sand. $\endgroup$ – farrenthorpe Aug 11 '14 at 22:57
10
$\begingroup$

I think the easy answer comes from the Hawaii Department of Land and Natural Resources:

Beaches in Hawaii may be made of 'black sand' derived from the erosion of volcanic rocks, of 'white sand' made by marine organisms, or a mixture of both. On the windward side of the Big Island, for example, black sand beaches are very common. The beach at South Point is almost entirely green sand composed of olivine, a common mineral found in the volcanic rocks here in Hawaii. On the Kona coast of the Big Island and on the other islands, the beaches have a range of mixed compositions, some with a high volcanic (detrital) component, some dominated by calcareous (reef-derived) sediment. Beach and submarine sands in Kailua Bay on windward Oahu (my research area) are almost entirely composed of calcarous, reef-derived material. On average, only about 5% of the sand grains are volcanic minerals or rock fragments. Every beach is unique and has its own source and type of sediments.

They even address some of the questions regarding "foreign import" here.

$\endgroup$
  • $\begingroup$ Out of curiosity, are there any yellow sand beaches in Hawaii? With quartz sand, so common elsewhere? $\endgroup$ – Gimelist Aug 7 '14 at 4:17
  • $\begingroup$ @Michael the green sands beaches have multiple colors ranging from gold to green. No mineral I know of is pure yellow (sulfur is not a mineral), but golden hue minerals are certainly in there. $\endgroup$ – farrenthorpe Aug 11 '14 at 22:55
  • 1
    $\begingroup$ @farrenthorpe quartz sand looks yellow. $\endgroup$ – Gimelist Dec 11 '14 at 7:47
  • $\begingroup$ Yes in Hawaii we call them white sand beaches but you are right they are more yellow than white in actuality. The further north you go up the Hawaiian chain (away from the hot spot, older geology), the more white sands beaches there are. In fact, Maui, and Big Island are the only two that have a lot of black sand beaches. $\endgroup$ – farrenthorpe Dec 11 '14 at 11:09

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.