Cool air causes the rock to harden on the outside, and when all the lava has drained out, the tube becomes a cave. Sea Cave Sea caves are formed by waves crashing on rocky coastlines. Ice Cave Ice caves are formed by water flowing underneath glaciers of ice.
Light passing through the ice makes the caves blue.
This teacher packet was originally available in printed format. The online edition contains full text from the original publication. Some images have been modified or added to improve the scientific visualization of information. All poster text and images are available under the Poster section. The Master Sheets and Activity Sheets are in PDF format.