It is, apparently, midterm season, and the site is currently being inundated by a large number of problem statement questions, duplicate questions, and other low-quality questions, which means that the review queues (particularly the "Close" review queue) is experiencing quite a backlog: there are currently over 500 questions in need of review.
This is a friendly reminder that anyone with sufficient reputation is able (and encouraged!) to wade into the review queues and help with the janitorial duties of site moderation. For those unfamiliar with the process, the review queues can be access from a drop-down at the top-right of nearly every page on the site.
Information on the process of reviewing can be found in the Help Pages. Further advice can be found in a FAQ.