A "crack" doesn't happen all at once when you're roasting. It takes a few minutes after the crack starts before enough beans have gone through the process to say the crack is done.
A "City" roast makes itself known by the first few beans hitting the second crack. Once you're well into the second crack, it's called City+, then City++. After the second crack is done, you've got a very dark roast indeed.
There are only two cracks. As I recall, coffee burns and disintegrates before it can third crack -- but I'm not a roaster.
People associate espresso with a very dark roast, but the dark, complex flavor is more a product of the brewing method than the roast. When you use a true espresso machine, the best roasts are usually medium or not much darker -- in other words, "City."
Starbucks uses an almost unique roasting method -- actually a slightly extreme variation of Peet's. Starbucks roasts very hot, very fast and very dark. Many people, me among them, think their beans are way too done on the outside, and still a bit uncooked in the center. It's not a very pleasant straight espresso.
On the other hand, Peet's, which is close to Starbucks but not quite as tweaked, makes for a very pleasant cup from a "French Press" aka cafetiere.
New question: What's the difference between marinating and brining?