|Piece of basalt from near Mauna Kea summit.|
I find this piece of rock fascinating for three reasons:
- It has a piece of another rock inside it. This piece is a flake off a larger rock, indicating that that rock cooled with this little bit of...something...inside it. The little embedded rock fascinates me as well, because I don't know what it is. My first guess would be 'basalt', since a) that's what everything on the island is anyway, and b) it comes from the top of a volcano. It has a sort of basalt-y look to it. It also has a kind of glassy look to it that makes me think it could be obsidian, volcanic glass. Apparently the lava that surrounds the little piece was below its melting point, else it would have melted away completely, but you can see that it shrank more than the surrounding lava as it cooled, forming the little air pockets around it. Altogether fascinating.
- It shows clear signs of layers, or strata, rather like sedimentary rock. It certainly makes sense that lava should have layers, since it erupts over previous deposits, but seeing so many layers in one rock is an experience I haven't had before. They were apparently laid down in different conditions -- note the different colors of the layers, and the differing amounts and sizes of the bubbles within them -- but what those conditions were I cannot say. It's possible the little embedded something fell onto a layer of lava and was then covered by another to form this rock (I think that's the most likely story). Another scintillating mystery.
- It's a piece of cooled lava! This thing has been through pressures and heats I can barely imagine, coming from deeper below the surface of the Earth than I've ever been above it, all to end up as a piece of rock you can hold in your hand. How cool is that?