T4W4 9SCI Magnetic Striping and Seafloor Spreading

What is magnetic striping on the seafloor?

• Stripes made of different types of rocks

• Patterns of rock that show magnetic polarity reversals over time

• Stripes caused by waves moving sand on the ocean floor

• Patterns formed by earthquakes

How does magnetic striping provide evidence for seafloor spreading?

• It shows that rocks at the seafloor are older than land rocks

• It shows that the seafloor is made entirely of magnetic minerals

• It shows symmetrical patterns of magnetic polarity on either side of mid-ocean ridges

• It shows that rocks are constantly eroded at mid-ocean ridges leaving behind the magnetic rock material

What causes the magnetic stripes on the seafloor?

• Earth’s magnetic field reversals recorded in cooling magma

• The movement of underwater animals that are attracted to magnetic rocks

• Erosion from ocean currents

• Seafloor earthquakes

Where are magnetic stripes on the seafloor found?

• At the edges of tectonic plates

• Along the coastlines

• On either side of mid-ocean ridges

• In deep-sea trenches

What happens during a magnetic reversal?

• The Earth’s magnetic field disappears and reappears millions of years later

• The magnetic north and south poles switch places

• The Earth’s magnetic field strengthens

• Ocean currents change direction

How do magnetic stripes support the theory of plate tectonics?

• They show that the Earth’s magnetic field is constant

• They indicate that new seafloor forms at mid-ocean ridges and moves outward

• They prove that earthquakes are common in the ocean

• They show that plates move only at mid-ocean ridges

Why are the magnetic stripes on the seafloor symmetrical?

• Rocks are deposited evenly by ocean currents

• Magma at mid-ocean ridges cools in patterns that reflect magnetic reversals equally on both sides

• The magnetic field is stronger on one side of the ridge which leaves a striping pattern compared to the other side

• Seafloor spreading occurs only on one side of the ridge

What does seafloor spreading explain about the movement of tectonic plates?

• Plates are static and do not move

• Plates move apart as new crust forms at mid-ocean ridges

• Plates move together at mid-ocean ridges

• Plates only move in one direction

Why do older rocks on the seafloor show different magnetic orientations?

• They were shifted by earthquakes

• They record past changes in Earth's magnetic field orientation

• They were formed at different mid-ocean ridges

• They were eroded by ocean currents

What is the relationship between magnetic striping and the age of oceanic crust?

• The closer to the mid-ocean ridge, the older the crust

• The further from the mid-ocean ridge, the younger the crust

• Crust is older as you move away from the mid-ocean ridge

• All oceanic crust is the same age