My wife just noticed a dip in our backyard that wasn't there previously.
It's probably a foot long, 6 inches wide, and 6 inches deep at most.

Aside from monitoring it, is there anything proactive I can do to
prevent/reduce damage?

When we moved in a year ago an orange marker had been placed about 5
feet east of this dip so I was wondering if perhaps a pipe of some kind
may have burst creating a cavity that is collapsing. Who would I call
to find out if this happened? My parents had something similar on their
house and had half the front yard excavated, if I recall the amount they
paid was substantial.

My bigger worry is that it's actually a sinkhole. We're in an extreme
drought (Williamson County in Texas) and I know the area (Central Texas)
is known for aquifers/caves. How do I even begin in detecting this and
is there a remedy aside from moving out? Does insurance typically cover
this should a giant hole form in my backyard (and potentially suck up my
house)?

Maybe it's just dirty sinking in where someone had dug a trench
previously, but I only know that the ground was marked and that was over
a year ago with no sinking until recently.

Any other reasons the ground may have sunk?

Thanks!

--
gorf