Archaeologists can use instruments that measure small variations in magnetic field to locate buried walls made of fired brick, . When fired, the magnetic moments in the clay become randomly aligned; as the clay cools, the magnetic moments line up with the earth’s field and retain this alignment even if the bricks are subsequently moved. Explain how this leads to a measurable magnetic field variation over a buried wall.

Archaeologists can use instruments that measure small variations in magnetic field to locate buried walls made of fired brick, . When fired, the magnetic moments in the clay become randomly aligned; as the clay cools, the magnetic moments line up with the earth’s field and retain this alignment even if the bricks are subsequently moved. Explain how this leads to a measurable magnetic field variation over a buried wall.