There's a fracture in time that starts in the future and leads one way to the cretaceous. A probe was sent through this fracture into the past and it was never found in the future, so they concluded that the fracture leads to an alternate time stream. Because of some kind of war, the atmosphere in the future becomes unbreathable without resperator masks. A select few are chosen -- some by lottery, some because they have extraordinary skills -- to travel back to the alternate cretaceous, (aka Terra Nova), to start civilization over and try to get it right. Our heroes are the family of a cop who broke the rules and was put in jail. His wife and family are chosen for Terra Nova because his wife is a doctor. She springs him outa the joint and he manages to get past security to Terra Nova, where his wife reveals that they'd brought their third child along. (There's a two child law.)
I won't reveal more because it would get into spoilers, but the plot from there revolves around three things. Immediately, the cop's eldest kid is a boy, (two girls), and while his wife and daughters welcome him back to the family, his son isn't letting bygones be bygones so easily; he's a teen rebel. Generally, the Terra Nova colonists rank themselves according to which "pilgrimage" they arrived in, but for reasons as yet unknown, the 6th pilgrimage, (sixers), were rebels; they broke away from the colony and started their own and the two colonies are at war. Long term, there are mysterious marks in the rocks by a natural pool; some kind of geometric formula, apparently of human origin and neither colony knows what they mean. Oh, and there are big, nasty dinosaurs that eat people.
This brings me to my first quibble with Terra Nova. The colonists are armed with what look to my inexperienced eyes like P90s left over from Star Gate. They're not very effective against big, hungry dinos, although they're pretty good against other colonists. If the purpose of the small arms is to repel dinosaurs, shouldn't they have small arms that are effective against dinosaurs? AA12s, for instance, or even elephant guns?
The acting is about what you'd expect from an American action series; overblown emotions, right up in your face, about as subtle as the dinos. There are the usual asortment of characters from the comedia del hollywood; the wise, old soldier; the young turk; the devoted wify; the rebelious, mouthy teenager; the dopey teenager; the bad girl; the good girl; the cute, innocent rugrat; the wiley enemy; the dopey enemy; etc, etc... And dinosaurs, lots of nifty dinosaurs! Honestly, sometimes the CGI dinos are more real than the actors!
I won't even bother with he science behind Terra Nova, it's clearly made-up from whole cloth with a dab of Stockholm Interpretation applied for the sake of verisimilitude.
So to sum up, Terra Nova is about average for American TV. There are no big surprises. The two-hour premiere episode hung together reasonably well. I probably won't bother about future episodes, though. Even nifty dinosaurs can't save it for this little otter.