Why is my pumpkin pie filling separating from my cake mix? I decided to mix pumpkin pie filling into a mixture of spice cake mix. I mixed the filling in well and in every try, the filling stays in the middle, with the cake moving to the outside.

I am wondering why this happens and if there is a way to control this separation, since I am seeing more cake moving to the top and just a thin layer on the bottom.

Update:
I did not alter the cake recipe and i just pored the pie filling directly from the can into the completely mixed cake mix. Mixed them together and pored into the pan. I did not change the baking time or temperature.
I wonder if this has something to do with the density of the cake vs the pie filling. This may be a similar phenomenon as when chocolate chips or nuts sink to the bottom of a brownie during cooking. 

I am not entirely sure how to solve this but one thing to try would be to mix the pie filling with the wet ingredients for the spice cake mix and then mix it all together. My hypothesis is that the pie filling isn't incorporated into the cake mix well enough (even though it may look well incorporated) and mixing it with the wet ingredients thoroughly may allow the eggs (i'm assuming eggs were involved) to set the mixture as a whole more evenly.