Sediment and airlock activity one hour after pitching yeast?

About one hour after pitching the yeast, there is already some activity in the airlock! Infrequent bubbling, but I didn't know it could happen so quickly. There is also sedimentation in the bottom of the carboy...about 1 1/2 inches!

This is my first time using a carboy, and not a bucket, so maybe the sediment happens with each brew and I never saw it? This is also the first time I used a starter, as well as an aeration system (it's only my 3rd brew).

I used a brown ale kit that I bought online about 2 months ago, and the WLP005 yeast was one week from its "best by" date. Yeast calculators said its only about 16% viable. So I made a starter, and then found out the cell count was still way too low. Since I didn't have time to step up the starter I bought another vial of WLP005 at my LHBS. This one was about 3 weeks old, so I figured combining the starter and new vial I should have enough yeast.
I poured the cooled wort (74 degrees) into a bucket using a strainer, then topped it off to just over 5 gallons,
I then poured it into the carboy. Lots of foam! I then aerated it for about 17 minutes, and a lot of foam came out the top. I then pitched the yeast along with some yeast nutrient.
In about an hour there was infrequent bubbling in the airlock, and a LOT of sediment visible. It was two tone...about an inch or so of light grey-ish and some darker sediment on top of that.

Is this normal?

Yes.

Fermenting in a carboy is much cooler then a bucket. You'll start seeing exactly what happens. Looks like someone is churning the beer with a stick! Keep an eye on it! Our 3 year old loves to watch it.

That much sediment that quickly has to be break material. However, good work on the starter & extra vial correction. You'll find your fermentations much more healthy with starters, I think!

WOW! I checked it this am (9 1/2 hrs after pitching) and the airlock was bubbling pretty good. I checked again at about 10:30 (about 15 hrs after pitching) and its bubbling through the airlock! Good thing I caught it when I did, and put a blow off hose in. I can't believe how much its bubbling through the blow off hose!

It's incredible the difference proper amounts of yeast and aeration make!

The only "problem" I have now is that the blow off tube doesn't fit perfectly snug into the carboy. There was some (very slight) bubbling escaping through the top of the carboy. I pulled out the hose and wrapped it in some sanitized aluminum foil. Not a perfect fit, but much better.

Anyone have any suggestions to solve this "issue"?

I would ASSUME that with the pressure of the CO2 that there isn't much risk of infection at this point. Once the bubbling slows I will put the airlock back on.