Compare pictures of different volcanoes. Then visit NASA's Space Place to learn about volcanoes and answer questions about volcanic eruptions.

Students examine satellite images of a recently formed island to identify areas of erosion and deposition.

This learning activity uses data acquired by the TOPEX/Poseidon altimeter, a joint project of NASA and the French Space Agency, to investigate the relationship between the topography of a sea-floor feature and the topography of the overlying sea surface.