Thursday, February 7, 2013

Green Sand

 Back to our adventures on the Big Island!  While there I had the bright idea to visit a green sand beach, which can only be accessed by foot or very serious 4 wheel drive.  No problems, Case walks over a mile to and from school every day.  We figured it would be worth it, as there are only two green sand beaches in the world.  The other one is in the Galapagos, and hence even harder to reach.
 The directions we received were a bit vague.  I read between 1 1/2 and 2 1/2 miles.  Having done it myself, I'm guessing it was closer to 2 1/2.  Case was not really happy with the distance, but marched along pretty well.
 When we reached the cliff overlooking the beach though it was stunning.  The ocean was ridiculously blue and clear. 
 We hiked down the cliff and dove in.  Case found a snail and parked himself in the glittering crystal sand.
See how green the sand is?  It was actually slightly more green in person. 
The visitor center at Hawaii Volcanoes National Park says that the lava there is unusually rich in olivine.  Olivine is present in most lava, and like most lava, the rocks on land there are black, but if you look closely you see very small flecks of green.  Olivine is green due to the presence of iron and magnesium, which makes it tougher and more dense than the rest of the rock.  When the lava here breaks down the less dense silicate materials are washed away more quickly, causing the olivine crystals to build up on the beach.

When olivine crystals are large enough they are known as peridot.  These crystals were pretty tiny, but quite striking when you have an entire beach made of them.

6 comments:

Rockwood said...

That is pretty cool. Case looks like he had fun once he was there. That olivine is pretty stuff for sand. See you soon!

deb said...

Case looks delighted digged in that green sand ---oh, I can't wait to see all of you.

Pat said...

Love the pictures... and it looks like you had the beach all to yourselves. Your recent posts have made me want to visit the Big Island again. Thanks!

Jill T said...

Thanks for the science behind it, Rob and I have been really into rocks lately so it was nice to learn a little bit more. That is so cool.

rachel said...

That is amazing! Thank you for the lesson and the awesome pictures. I'm trying to imagine a beach made of sand made up of my birthstone. That's just cool.

Lara said...

So pretty. I was bummed when you reminded me that this is on the Big Island and that we probably won't be going there this week. On a brighter note, we leave tomorrow!