14
Superposition
(way to get relative ages)
(way to get relative ages)
•Newer
features are superposed
on top of older ones
on top of older ones
•Large
impact forms basin
•Basin
floods with lava
•Additional
impacts occur in mare lava
•Over
time both crater rate and volcanic activity are declining
–Craters
less because debris swept up
–Volcanism
less because moon cooling
From our text: Horizons by Seeds