This is a closer picture of that bundle of floor layers. Do you see what is under them?
That's right. Someone found a layer of broken pottery and, rather than clean it away, someone probably just piled dirt to level it out and then built their floor above it. And the next layer went over that, and so on.
So the diggers had to carefully remove a layer at a time, knowing that eventually they would get to a huge amount of broken pots.
By the way, why do you have to go down a layer at a time? Because you can't find out when a floor was made by what's on top of it, only by what's in it or under it. If the floor stands on top of a coin from 40 BCE, then the floor could not have been built in 41 BCE.
One of the bosses explained the fallacy of looking at what's above instead of what's below. "See that stone floor? What's on top of it? A picnic table! So the floor must be from the plastic era."