What is paleomagnetism?

Paleomagnetism refers to the remnant magnetism that is preserved in rock bodies as they cool and solidify from molten material. When igneous rocks form, magnetic minerals within them align with the Earth's magnetic field at that time. This alignment can be locked in as the rock solidifies, effectively capturing the direction and intensity of the magnetic field during that period.

Studying this remnant magnetism allows geologists to reconstruct the historical magnetic field of the Earth, providing insights into plate tectonics, continental drift, and the geological history of the planet. This makes paleomagnetism an essential tool for understanding the past movements of the Earth’s continents and the geological processes that have shaped them over millions of years.

The other options describe different geological phenomena that do not relate to the remnants of magnetic fields in rocks. For instance, ancient seismic activities focus on past earthquakes, oceanic crust formation pertains to the processes that create new ocean floor, and the formation of mountain ranges involves tectonic forces and uplift rather than magnetic properties of rocks.