What causes magnetic stripes on the seafloor, such as those shown here?
A)Volcanic rocks in oceanic crust are covered by a variable thickness of sediment.
B)Some oceanic crust consists of volcanic rocks and some is composed of sediment.
C)Sometimes Earth's magnetic field points north and sometimes it points south.
D)Some volcanic rocks are formed in normal ways and others have pillows.

Question

What causes magnetic stripes on the seafloor, such as those shown here? 
A)Volcanic rocks in oceanic crust are covered by a variable thickness of sediment. 
B)Some oceanic crust consists of volcanic rocks and some is composed of sediment. 
C)Sometimes Earth's magnetic field points north and sometimes it points south. 
D)Some volcanic rocks are formed in normal ways and others have pillows.

Quizplus · Accepted Answer

The magnetic stripes on the seafloor are caused by variations in Earth's magnetic field. As molten magma rises and cools to form new oceanic crust, the minerals in the magma align themselves with Earth's magnetic field. At times when the magnetic field points north, the minerals align in a certain way, creating a "normal" polarity. At times when the field points south, the minerals align in the opposite way, creating a "reversed" polarity. As new crust is formed and the magnetic field changes direction, these polarity changes are recorded in the rocks, creating the magnetic stripes.

What Causes Magnetic Stripes on the Seafloor, Such as Those