Once the quest " Eyes of Magnus " is done; speak to Tolfdir and he'll give you this quest. He tells you that ruptures have appeared throughout Skyrim thanks to Ancano's meddling with the Eye. You now need the Staff of Magnus to close them.
Bring your Staff along and fast travel to the closest location to where the marker is and go to it. Some Anomalies pop out, so take them out and shut the rupture. That's it. Return to the College to receive your payment. 1500 Gold! Wow! Note that this quest can be taken again and again (for as long as you want).