This may not be 'our Earth'. What have they done to let us believe this is the Earth we know. The have not shown the moon or any other solar objects that we could reconize, also no reconizable land masses or anthing Earth specific. We know from Tyrol's flashback that they had cars of some sort, but they never showed them, we only heard them.
I believe that this is RDM's way of pulling the OldBsg's Terra element on us.
I'm not fully convinced this is earth, either. It would have been nice to see something giving us more solid confirmation that this is 'our' earth, like (as you said) recognizable land masses or even signage in the flashbacks indicating an earth city (a sign with 'City of New York' or a piece of garbage with a Microsoft logo--something along those lines would have sufficed).
I realize that the nuclear holocaust that destroyed this earth may have occurred hundreds or thousands of years after 'our' era, and things like New York city and Microsoft may have been renamed or simply don't exist by that point in the planet's history but if it indeed is our earth, I'd like to see something definite confirming that.
Until we get that, I'm not completely convinced that the planet we're seeing on BSG is the same planet we're all living on.