What does magnetic striping on the sea floor indicate?

What does magnetic striping on the sea floor indicate?

• A. Alternating stripes of different directions of magnetic polarity in rock on the sea floor
• B. A uniform polarity of rocks on the sea floor
• C. No relation to Earth's magnetism
• D. Random magnetism due to current flows

Answer: (A)

Magnetic striping on the sea floor records Earth's magnetic field reversals as new rock forms at mid-ocean ridges. When magma erupts and cools into basalt, the iron minerals inside align with the current direction of Earth’s magnetic field and lock in that polarity as the rock solidifies. Over geological time, the field has flipped many times, so successive layers record alternating normal and reversed polarity. As the seafloor spreads, new rock forms at the ridge and pushes older rock outward, creating mirrored stripes on both sides of the ridge. This clear, patterned record of alternating polarity is the evidence that the sea floor is spreading and that Earth’s magnetic field has varied in polarity.

Magnetic striping on the sea floor records Earth's magnetic field reversals as new rock forms at mid-ocean ridges. When magma erupts and cools into basalt, the iron minerals inside align with the current direction of Earth’s magnetic field and lock in that polarity as the rock solidifies. Over geological time, the field has flipped many times, so successive layers record alternating normal and reversed polarity. As the seafloor spreads, new rock forms at the ridge and pushes older rock outward, creating mirrored stripes on both sides of the ridge. This clear, patterned record of alternating polarity is the evidence that the sea floor is spreading and that Earth’s magnetic field has varied in polarity.