These craters are relatively recent additions to the moon's surface (within the last billion years :) Note the many small craters between Copernicus on the left and Eratosthenes on the right. These small craters are secondary craters caused by ejecta thrown out from the Copernicus impact.

Also note between these two craters is the ghostly remains of the crater Stadius which has been mostly submerged in lava that flowed into it eons after it was created.