krausen falls but still vigorously fermenting ???

just wondering if anyone has observed this and/or knows anything about it...
i did a 10 gallon batch yesterday (22 lbs. belgian pils, 2 lbs. malted wheat - decoction mash) and split it into two carboys. i pitched a fairly active starter of whitelabs 565 on one and a well inflated smack pack (mfg date + april 26th!) of wyeast 3787 on the other, the later essentially being a "starter" for a tripel that i'm going to brew next weekend.
so when i went to bed last night (6 hours after pitching), they both were starting to bubble about once every two seconds and were forming a thin, creamy krausen. this morning (12 hours) they were both looking like they were heading into high krausen, bubbling pretty furiously, and the 3787 batch was rapidly circulating from convection currents.
the weird thing is that when i came home from work (24 hours after pitching) and was expecting them to still be getting into high krausen, they had both fallen completely. the 3787 is still has a lot of convection going on and is bubbling more than once a second.
so anyone have an idea why the krausen fell to the bottom? is this characteristic of the yeast? it's my understanding (and experience, if memory serves correctly) that the krausen doesn't fall until the rhu beer (is that the correct term?) is getting close to being finished.
i guess i should take a gravity reading to see, but i don't really wanna mess with it.

i should have given these specs.
o.g. 1.063
temp. 76 deg. f

I would say that it will finish soon but the only real way is to take a gravity reading. I would just let it go and not worry. As long as it is churning away you are good.

weird, i went in to check it a couple of hours ago. it is still bubbling away and has again formed about a one inch krausen. ! go figure, there are way less chunky masses circulating in suspension.
i guess this can turn into a yeast geek thread ... or forget it; all systems go.
thanks for the encouragement anyway.

How's your beer turn out when the krausen fell and reformed? Just happened to me for the 1st time and I'm not concerned (since it's still bubbling away) but am curious as to why. It happened to me with an English Brown Ale using S-04 on an OG 1.040 beer at 68-70F. Krausen fell after 48 hrs, yet still bubbling away just as much.

He hasn't been on the board since May 13, 2008... Krausen falling really doesn't determine a finished fermentation. A consistent final OG does. Probably just fell due to the fermentation being at a different stage.