The state of equilibrium between the Earth's lithosphere and the underlying asthenosphere, maintained by the buoyancy of the lithosphere.
Isostasy
First discovered isostasy and observed reduced deflection of plumb lines in the Andes.
George Everest
The depth at which the weight of the crust is balanced by the buoyancy of the mantle.
Compensation depth
The part of the crust directly beneath a mountain that extends deep into the mantle and has lower density, preventing sinking.
Root zone
A model of isostasy that assumes the crust of constant density floats on a denser mantle, with higher elevation corresponding to deeper roots.
Airy-Heiskanen Model
A model of isostasy that assumes topography varies inversely to density, with higher elevation corresponding to lower density of rocks.
Pratty-Hayford Model
A model of isostasy that explains isostatic compensation as a regional phenomenon, with the crust behaving as an elastic material that bends downward due to topographic load.
Vening Meinesz Elastic Plate Model
The process by which the lithosphere floats back to its original position after being pushed down by mountains or other features.
Isostatic rebound
Uplift caused by a lowering of elevation after erosion of a mountain, resulting in a deeper root zone.
Overcompensation
Subsidence caused by an increase in elevation due to additional load, resulting in a shallower root zone.
Undercompensation
The angle formed between the magnetic north of a compass and the true geographical north.
Magnetic Declination
Points on the Earth's surface with a common magnetic declination value.
Isogonic lines
The angle formed between the Earth's surface and the planet's magnetic lines.
Magnetic Inclination
The location with zero magnetic dip, present at the equator.
Aclinic line
Property of materials that are repelled by a magnetic field, with all electron spins paired.
Diamagnetism
Property of materials that are weakly attracted by a magnetic field, due to the presence of unpaired electrons.
Paramagnetism
Property of materials that become magnetized and remain magnetized, with atomic magnetic moments parallel to the external magnetic field.
Ferromagnetism
Property of materials with spins pointing in opposite directions, which may exist at low temperatures but vanishes at and above the Néel temperature.
Antiferromagnetism
Property of materials where the magnetic moments are unequal in magnitude, resulting in a spontaneous magnetization.
Ferrimagnetism
The difference between the measured magnetic field of the Earth and that which would be expected from the International Geomagnetic Reference Field (IGRF).
Magnetic anomaly
The alignment of minerals in the current magnetic field.
Induced magnetization
The magnetization left behind in a ferromagnetic material after an external magnetic field is removed.
Remanence
The ratio of the intensity of induced magnetization to that of remanent magnetization.
Königsberger ratio (Qn)
A magnetometer composed of nickel-iron alloys that measures the strength of the magnetic field along its axis.
Flux-gate magnetometer
A magnetometer that measures the frequency of precession of protons in a proton-rich liquid, proportional to the Earth's magnetic field.
Proton-precession magnetometer (PPM)
A magnetometer that utilizes the Zeeman effect in vapors of alkali elements to measure the strength of the magnetic field.
Absorption-cell magnetometer