Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

What statement describes the outer core?

1. It is solid and dense

2. It is more viscous than the mantle

3. It is primarily made of silicon

4. It is the hottest layer of the Earth

The correct answer is: It is more viscous than the mantle

The outer core is best characterized as being liquid and composed largely of iron and nickel. Its viscosity is significant, but it is described as less viscous than the mantle, which is semi-solid and behaves like a viscous fluid over long periods. The outer core transitions from solid materials found in the mantle to the liquid state due to higher temperatures and pressure conditions. This transition leads to the generation of the Earth's magnetic field through the movement of the molten metal within. While the outer core is extremely hot, particularly compared to layers above it, the statement about its viscosity provides a clearer distinction about its state compared to the mantle. The outer core's characteristics align with its role in the Earth's geodynamo and magnetic properties, setting it apart from the solid nature of the inner core or the elements found in the upper layers of the Earth.