satellite view from PMNM
E komo mai; welcome! Midway Atoll National Wildlife Refuge is surrounded by a lei of foam in the middle of the North Pacific; it's a beautiful, special place.

Not only are there albatross on Midway, but many other interesting kinds of wildlife, both on the land and in the sea. Please enjoy exploring FOAM, an educational blog actively done while on Midway from May through August 2010. Posts are added from off-Midway, as information becomes available. If you're interested in a particular topic, please use the search box or the alphabetical list of "labels" along the left side of the blog page.

Thursday, August 5, 2010

Midway Atoll Rock Challenge -- answers!

Don't look at this post until you've tried the Midway Atoll Rock Challenge in the previous post!

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Heeeeeere's the answer!

From the picture, you can probably see that #5 has pieces of different colors; it's the cement.

And #9 is the coral.  If you look closely, you can see the small spots or holes where coral animals lived when the rock was part of a living coral colony.

But if you can't tell which rock is pumice by looking at it, you can test to see if it floats.  Yes!  Pumice floats!

When I put all 10 rocks into this pitcher of water, the 8 pieces of pumice floated, while the cement and coral sank.  No wonder flying fish, which live at the ocean's surface, attach their eggs to pumice.

cement on the left; coral on the right


Susan said...

cool! i like the water test. i know that bone sinks, so that's an easy way to test that, at least in homemade chicken soup or something.

Barb said...

Yes, it IS cool to the water test!

As far as I know, pumice is the only rock that floats. Lava erupts out of a volcano, and some of the lava encloses air as it becomes solid. That's what pumice is: rock with lots of air spaces trapped inside. No wonder it floats!