Earth's Magnetic Field and Volcanic Rocks

What is the primary function of Earth's magnetic field?

• To generate heat within the Earth's core.

• To cause volcanic eruptions.

• To protect the planet from harmful solar radiation.

• To create ocean currents.

How do volcanic rocks preserve a record of Earth's magnetic field?

• They absorb cosmic rays, which then align.

• Iron particles within the molten lava align with the magnetic field as it cools.

• The heat from the lava permanently magnetizes the surrounding soil.

• They chemically react with the magnetic field, changing their composition.

What surprising discovery did Bernard Brunhes make about Earth's magnetic field by studying ancient volcanic rocks?

• The magnetic field is slowly increasing in strength.

• The magnetic field has remained constant throughout Earth's history.

• The magnetic field has reversed its direction multiple times in the past.

• The magnetic field is strongest at the equator.

Approximately how many times has Earth's magnetic field reversed in the last 20 million years?

• Once every million years.

• About 60 times.

• Only a few times.

• It has never reversed.

What was a major consequence for Mars after its magnetic field disappeared?

• It became a gas giant.

• Its atmosphere became thicker.

• Harmful cosmic and solar rays bombarded the planet.

• It developed a strong gravitational pull.