If you swirl the fermenter that stuff will settle again. At this point it's unlikely you have much if any krausen on top of the beer. At the peak of fermentation, you can have 1-4" of krausen on top of the beer. It's held there by the bubbles of CO2 the yeast are producing. When fermentation slows, the krausen falls, as there no longer is enough CO2 to keep the "head" up to those levels. Sort of like head on a beer; when the beer goes flat, no head.
But if you still have a layer of krausen on the top of the beer, it's probably not done. What you may have on top of the beer are yeast rafts which will sink down over a few days. It doesn't seem likely you still have fermentation ongoing as your airlock has ceased bubbling. The only thing would be if there's a leak through which CO2 is escaping, instead of the airlock. Unlikely given the airlock has worked fine to this point.
What yeast rafts look like:
https://www.google.com/search?tbm=i...0KHbzGAHMQ4dUDCAY&uact=5#imgrc=a2Ry4WCznQflMM:
I personally would not swirl it, but there's nothing wrong with doing that. You had a temp which would promote good yeast activity, but not too high. Bubbling has stopped.
Agree with
@Bigdaddyale that you can let the temp rise a few degrees; this will help the yeast clean up after itself (yeah, they really do), but if you're already at 70 degrees, that won't do all that much more than just letting it sit. Most ales I ferment at about 64 degrees, then I let it rise to 71 degrees at the end. You're already there.
You didn't say what kind of fermenter you're using. If it's clear you can see what the krausen is doing (why I like clear fermenters over white plastic buckets). If it's a bucket you're using--and that's fine if you are--maybe you can see a little bit through the side with a flashlight. There will be krausen stuck to the side of the bucket, but the surface of the beer will be largely clear of krausen, just some minor flotsam and jetsam still on the surface.
Anyway, congrats--what you've seen is perfectly normal. A 4-day fermentation is typical. Depending on the temp of the wort, and the strain of yeast, your fermentation can be over in as short as 2 days (I just had one do that--lager yeast at ale ferm temps), and as long as...well, days and days, if you have a slow lager yeast fermenting at cool temps (48 degrees, say). Chemical and biological processes proceed faster at higher temps.
And BTW, your patience is exemplary. Of all the things we need to learn as brewers, including bizarre language including terms such as strike water, tun, sparge, hydrometer, krausen, yeast rafts, and many many more, the single hardest thing for new brewers to learn is....patience.
