Hey, I'll openly admit that we certainly don't understand everything about how evolution occurred over the last 3.5 billion years (though we can say for sure that it has happened and continues to do so). It is good to question the assumptions about what we know in science, but if one expects an existing model to be replaced, one must offer up something better than the existing model that is capable of explaining more. That's what burns me about ID - it doesn't offer any explanations of how change occurs, and hasn't contributed anything other than pointing out we don't know everything yet (something we already knew!)
You make a good analogy to tectonics. Tectonics works in "spurts" - small "jolts" that over time add up to colossal changes - but it still, on average, is a gradual process. Evolution may work more in this manner than we think, but we're still talking about a gradual process when considered in the grand scheme of time. There certainly are many examples of documented gradualism known in evolution, but we don't know for certain yet that this type of change explains every instance of evolution, I would agree. This, though, is merely the meting out one of the finer details of the theory, not changing its basic precepts all together.
Doesn't mean there aren't some "gradual changes", but it's the big stuff that counts most ~
As far as evolution goes, it does seem to be "gradual" if you look over the continuum from 4 billion years ago to the present time. However, for the first 3.6+/- billion years NOTHING HAPPENED.
There seems to have been bacterial mats.
Finally, something happened and genetic change started happening ~
That, by itself, is a great mystery. No one has any good idea about why evolution, if it works, didn't bother working for such a long period of time ~ actually, most of the time!