Why are areas of the lawns "spongy" ?

[MowerMark]

There are green areas of seemingly normal grass, but when walking on these areas it feels like there's foam underneath. . . an extra thickness. Is this thatch?

 

[bertsmobile1]

Grass growing consumes the soil that is underneath so the spongy regions get top dressed

 

[MowerMark]

Grass growing consumes the soil that is underneath so the spongy regions get top dressed

There's an alternate explanation https://www.lawnmowerforum.com/show...ialists-state-this-lawn-is-normal-and-healthy

 

[kentatas]

Grass growing consumes the soil that is underneath so the spongy regions get top dressed

This can be one case. I think there is another situation wich can happen for this condition.

 

[MowerMark]

This can be one case. I think there is another situation wich can happen for this condition.

That condition being what ? Excess thatch? Grass deciding to grown about ground and rarely rooting into soil?