What is Blue Rock?

[Super8]

Hi,

Could someone explain what they mean when you're digging and you hit blue rock?
Is this it?

[url]http://en.wikipedia.org/wiki/File:Scoria_AmsterdamIsland_5.jpg
[/url]

Or could someone point me to some pictures or a diagram of the layers of the different kinds of earth on the Big Island?

Does anybody have a real close up picture of cracked earth from some of the more recent flows?

I found these pictures in a surf. If Allan is on here, thanks for the amazing stills.

http://www.laughtermedicine.us/hawaii/ka...index.html 4th, 5th, and 6th ones.

Looks like Scoria to me. Is blue rock underneath this stuff?

Thanks[8]