A youtube video came out 5 hours ago from someones journey in 2019. You can clearly see a LOT more barrels in it. There's also a helicopter
This is apparently a giant metal detector used for looking for possible mining locations!
https://geotech.ca/papers/helicopter-electromagnetic-vtem-ztem-applications-gold-exploration/
@xssfox People swing (smaller) metal detectors to search for submarines: https://en.wikipedia.org/wiki/Magnetic_anomaly_detector