fault line

noun
1
a place where there is a long break in the rock that forms the surface of the earth and where earthquakes are more likely to happen
گسل, خط گسل
2
an issue that people disagree about and may, as a result, lead to conflict
نقطه اختلاف, مسئله مناقشه‌برانگیز
The two men are from opposite sides of the nation's political fault line.