I made a strong Blonde this past Saturday (1.060) and pitched White Labs American Ale from a 600ml starter that night.
The next morning it was bubbling away with about two inches of krausen on top. Monday it was still pretty active but slowing down. Tuesday it was bubbling about half the rate from it's peak.
This morning I wake up and glance at the bubble lock, and it has a yeasty looking krausen in it. The 6 gallon carboy is filled with large, bubbly krausen but it still seems like the CO2 activity is about the same as it was on Tuesday.
What would cause the krausen to bubble up like that all of a sudden? It has been holding steady at about 2 inches or less until this morning. The temps haven't changed and I didn't agitate the carboy or open the top at all since I pitched.