What's going on underneath my trunk liner?
 

I noticed a heavy layer of dirt underneath the side "flap" covers in the trunk.

Pic 1: Left side: exactly as it appeared when first removing flap
https://cimg1.ibsrv.net/gimg/www.clu...775be76dc5.jpg

Pic 2: Right side: Already vacuumed before I took pic. The flat surfaces are cleaner, but you can see the original dirt level (same as left) on the white molex connector.

https://cimg3.ibsrv.net/gimg/www.clu...714bd2caa0.jpg

Question 1: Why is this dust here? Is this normal?

Question 2: Why does the right side have this textured-looking material on the horizontal surface, whereas the left side is smooth?

Pic 3, Question 3: This messy yellow/gold-ish application of some kind of plastic adhesive/sealant is all over the place. What is it? Is this standard?
https://cimg9.ibsrv.net/gimg/www.clu...35a59fb685.jpg


I am worried this all points to something bad happening to the car, although I'm not sure what... the rest of the trunk is clean, including the spare tire well. Any ideas? Thanks!

3- The yellow stuff is mastic or seam sealer. It's a sealer that sets pretty solid. It gets applied at the factory to seal spots where water could get trapped and cause rust. It's white when applied but goes yellow over the years.
2- As to the dirt, there is a vent just there into the fender so I would imagine either you or a former owner regularly drove somewhere that there was lots of dust like a gravel road.
1- The textured stuff is sound-deadener that kills off panel vibration. No idea why it's on the right side and not the left.

So long as it's not wet in there, just clean it up and forget about it.

Thank you! Feeling relieved. Although I am confused why there's a vent to the fender to let in dust straight to the stereo amplifier, etc.

https://jalopnik.com/heres-what-thos...-re-1828016409

Good article on what those vents are for.

Good point. Maybe the rubber flaps on your exhauster vents are damaged/missing and that is letting the dirt in.
Also if you or a previous owner was a heavy smoker, the amount of tar that builds up in places like that is surprising.