Alternating magnetic polarity of ocean crust either side of Mid-Atlantic Ridge and the crust gets older with distance from the ridge.
1 of 7
What is paleomagnetism?
Iron particle in lava erupted on the ocean floor are aligned with Earth's magnetic field. As the lavas solidify, these particles provide a permanent record of Earth's polarity at the time of eruption.
2 of 7
Approximately how often does Earth's polarity reverse?
Every 400,000 years.
3 of 7
What gave evidence of plates being destroyed to counteract sea-floor spreading?
Huge ocean trenches where large areas of ocean floor have been pulled down.
4 of 7
What forms hot spots in the mantle?
Radioactive decay of elements around the core.
5 of 7
What creates convection currents?
Lower parts of the asthenosphere heat up so become less dense and slowly rise. As they move up the diverge before cooling again, becoming more dense and sinking.
6 of 7
How do the convection currents move the plates?
They create drag along the base of the tectonic plates.
7 of 7
Other cards in this set
Card 2
Front
What is paleomagnetism?
Back
Iron particle in lava erupted on the ocean floor are aligned with Earth's magnetic field. As the lavas solidify, these particles provide a permanent record of Earth's polarity at the time of eruption.
Card 3
Front
Approximately how often does Earth's polarity reverse?
Back
Card 4
Front
What gave evidence of plates being destroyed to counteract sea-floor spreading?
Comments
No comments have yet been made