Analyzed lava flows over craters to determine relative age. ... As lava flows the surface cools and hardens leaving a hot core which continues flowing. ...
The Amu Darya, in the west, and the Syr Darya, in the east ... http://images.encarta.msn.com/xrefmedia/sharemed/targets/images/pho/t002/T0 02695A.jpg ...