The term used for the measurement of the Earth's magnetic field is "geomagnetism." This field is created by the movement of molten iron and other metals in the Earth's outer core, which generates electric currents that produce magnetic forces. Geomagnetism is critical for navigation since it impacts compasses and helps in mapping out locations. Scientists study geomagnetism to understand its variations over time, which can be influenced by cosmic events or human activities. Understanding the Earth's magnetic field is also important for studying the planet's geology and protecting satellites and power grids from geomagnetic disturbances.