Where limestones are born

Carbonate Lab

This is a tropical carbonate platform, cut open: a reef at the edge of the deep sea, a lagoon behind it, and tidal flats and salt flats on the shore. Almost every grain in these rocks was made right here, by living things or by the warm sea itself.

1. Where does it form? Each numbered pin marks a place where a different limestone is forming today.
2. How does it form, and what does it look like? Open a pin to watch it form in 3D, turn a hand specimen, and look at its thin section under the microscope, alongside real photographs.
3. What is it called? Each rock is named with the two classic schemes, Dunham and Folk, worked out from the thin section itself.

Open Sea level to drop the sea to a lowstand and flood it back: watch the reef step down the slope and the platform top turn to karst. Try Classify to build a rock of your own.