Sci Chapter 2 # 10: Sea Floor Spreading and Polar Reversal

Which of the following best defines the Mid-Ocean Ridge?

• An underwater mountain range created by sea floor spreading.

• A large underwater cave system created by erosion
• A type of underwater volcano caused by seismic activity
• A deep-sea trench formed by converging tectonic plates

What magnetic readings are detected in stripes of the ocean floor closest to the crest of ocean ridges?

• Random magnetic patterns
• No magnetic readings
• Stable magnetic field
• Normal polarity

Which term is best described as the creation of new oceanic crust due to the upwelling of magma?

• Crustal expansion
• Oceanic eruption
• Seafloor spreading
• Magma upsurge

Which best describes reversed polarity in relation to the rock stripes in the mid-Atlantic ridge?

• A magnetic field aligned in the opposite direction as the earth's present-day magnetic field.

• Uniform magnetic orientations
• No magnetic orientations
• Random magnetic orientations

How do the normal and reversed polarity of stripes of ocean floor prove that the earth's magnetic field has changed multiple times since its formation?

• The normal and reversed polarity of stripes on the ocean floor are a result of volcanic activity
• The normal and reversed polarity of stripes on the ocean floor are due to changes in ocean currents
• The normal and reversed polarity of stripes on the ocean floor are caused by Aqua Man and his pet octopus

• 1. It shows that the oceanic crust created by the upwelling of magma reflects the current magnetic field at that time, thus different polarities testify to a change.