There is a minefield.

Your "minefield" refers to that minefield, a minefield with weather reasons, a mine buried underground! Don't say you have seen the TV series War Thunder. If it is a mine, then many areas along the Sino-Vietnamese border are indeed "dead zone" minefields, because the underground magnetic field is strong, especially there are natural ore beds such as minerals, thus forming a magnetic field for guiding ore. Followed by coal seams, and some are caused by surface reasons. China is rich in coal resources and mine resources, so there are many minefields.