The home was built in 1930. Floor was covered with carpet at the finished portion. The unfinished area was in serviceable condition.
The house has moisture/mold/drainage issues.
What do you think caused the concrete displacement at the floor between the unfinished & finished areas?
The main girder & beams run parallel to the cracking. 90% of the beams & girders were covered with wall paper & drywall.
I don’t see a crack David, was it poured/formed like that?
Are the windows and doors square?
Possibly a cold joint with differential settling. Possibly they ran out of concrete.
From what I can see on the photo, the two floors were poured at different times and poured the way we see it.
It could be possible that one floor was poured while the door was not there and a guess was made on the floor elevation.
One of the two floors is also out of level.
It appears that the high floor was chipped away from another portion of a wall or floor at one point.
This area of the slab could lead to future water intrusion if there should be a drainage problem with the property and hydrostatic pressures of any kind.
JMO
Marcel 
Thanks for your responses to my question.
How would you report to your client pertaining to the cold joint between the floors?
Would you note as a safety concern as a possible tripping hazard.
Would you note as a repair? How would you explain repairing?
Thanks
This link explained a cold joint just as Mcyr & KS noted.
http://www.toolbase.org/ToolbaseResources/level4FAQ.aspx?ContentDetailID=1087&BucketID=3&CategoryID=33
David,
I would call out a trip hazard. I’d recommend repairs to smooth the transition from one floor level to the other, using approved material such as floor leveling compound installed by a qualified contractor.
I wouldn’t report or comment on what may be present in areas that are not visible, as that would be guesswork. The presence of a cold joint isn’t necessarily a bad thing, it’ s just a thing. Do your best on the moisture/mold/drainage issues and move on.
Stu
I agree with that.
Marcel