<Table> <Tr> <Td> </Td> <Td> This section does not cite any sources . Please help improve this section by adding citations to reliable sources . Unsourced material may be challenged and removed . (August 2011) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This section does not cite any sources . Please help improve this section by adding citations to reliable sources . Unsourced material may be challenged and removed . (August 2011) (Learn how and when to remove this template message) </Td> </Tr> <P> On the top of the lunar stratigraphical sequence rayed impact craters can be found . Such youngest craters belong to the Copernican unit . Below it can be found craters without the ray system, but with rather well developed impact crater morphology . This is the Eratosthenian unit . The two younger stratigraphical units can be found in crater sized spots on the Moon . Below them two extending strata can be found: mare units (earlier defined as Procellarian unit) and the Imbrium basin related ejecta and tectonic units (Imbrian units). Another impact basin related unit is the Nectarian unit, defined around the Nectarian Basin . At the bottom of the lunar stratigraphical sequence the pre-Nectarian unit of old crater plains can be found . The stratigraphy of Mercury is very similar to the lunar case . </P> <P> The lunar landscape is characterized by impact craters, their ejecta, a few volcanoes, hills, lava flows and depressions filled by magma . </P>

An area on the moon that is abundant with craters are generally referred to as