Is this a run-on sentence?
Archaeologists are unable to explain the mysterious structures in Jordan, Syria, and Turkey called "Big Circles," made of stones piled several feet high, the two-thousand-year-old circles are more than 1,300 feet in diameter.

Yes, technically.

Explanation:

A trick to try is saying the entire sentence out loud at a moderate pace in one breath.  If you find yourself running out of breath or it's difficult to finish then it is more than likely a run on sentence.

in "people in peace, not profit and war" chrisholm uses inductive reasoning for her argument against defense spending by stating that the new administration, like most americans, wanted to invest in social objectives, so they must not want to prioritize defense spending. mr. nixon said "we can delay no longer in launching new approaches to the problem that beset them", but chrisholm points out that the programs were delayed anyways.

well people will have to mark your answer as the best answer. and from that u receive crowns.

~batmans wife dun dun