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D. H. Matthews and F. J. Vine proposed an explanation of marine magnetic anomalies that combines seafloor spreading with reversals of the geomagnetic field. Newly formed magnetized material moves away from a ridge, preserving a sequence of polarities.^[ref]

The proposal turned magnetic profiles into a test of ocean-floor motion. The measured field also depends on source geometry and observation height, so it is not simply a local polarity reading.

Kalle Kiik coauthored a magnetic survey and subsurface model of the Lonar impact crater. The study compares measured magnetic anomalies with rock magnetic properties and the geometry of the surrounding Deccan Traps.^[ref]

A magnetic profile is the field of a three-dimensional source, not a direct section through it. Accounting for background magnetization and surface topography helps separate the crater-related signal from its surroundings.

An iron oxide exhibiting ferrimagnetism, $\gamma \text{-}\mathrm{F}{\mathrm{e}}_2{\mathrm{O}}_3$, that can contribute to geological magnetic anomalies.

Measurement of a magnetic field over a region to locate contrasts in subsurface magnetization. Temporal background changes and cultural interference must be distinguished from spatial magnetic anomalies.

Oceanic magnetic anomalies. Newly formed oceanic crust contains magnetic minerals. As it cools through their magnetic blocking temperatures, it acquires thermoremanent magnetization recording the ambient field polarity. Continuing seafloor spreading carries that record away from the ridge. Geomagnetic reversals therefore generate approximately paired marine magnetic stripes parallel to the ridge, with older crust farther from its axis. A magnetometer measures the superposed field above this magnetized material; subtracting a reference field reveals magnetic anomalies. The anomaly sign and shape depend on magnetization direction, latitude, source depth and geometry, so a positive measured anomaly is not universally identical to normal rock polarity.^[ref]

Matching a sequence of stripes to an independently dated reversal chronology gives plate ages and spreading histories. A stripe of width $w$ formed over interval $\Delta t$ implies half-spreading rate $v=w/\Delta t$ under steady symmetric spreading; full separation speed is $2v$. Unequal widths on opposite flanks can reflect asymmetric spreading or later deformation. Alteration, remagnetization and overlapping magnetic sources complicate inversion. The sequence correlation is stronger evidence than an isolated stripe or a field-strength peak.

Rayleigh-Bénard convection. Consider a horizontal fluid layer of thickness $d$, hotter below by $\Delta T>0$. The conductive state is motionless with a linear temperature gradient. A rising warm parcel is buoyant, but viscosity resists its motion and thermal diffusion erases its temperature anomaly. In the Boussinesq approximation, density variations are retained in buoyancy while the flow is otherwise incompressible. The competing effects are measured by the Rayleigh number and Prandtl number,For stress-free impermeable, fixed-temperature boundaries, linear stationary disturbances with horizontal wavenumber $q/d$ giveMinimizing gives $q_c=\pi /\sqrt{2}$ and the critical Rayleigh number for an isothermal layer, ${\mathrm{Ra}}_c=27{\pi }^4/4\simeq 657.5$. Two rigid no-slip, fixed-temperature boundaries instead give approximately $1708$; the critical value is not independent of boundary conditions.^[ref]

Above onset, buoyancy can sustain overturning rolls and heat transfer exceeds pure conduction, with Nusselt number $\mathrm{Nu}>1$. Nonlinear advection eventually limits the disturbance; larger driving can produce time-dependent or turbulent states. The ideal Boussinesq problem does not require hexagonal cells: planform selection depends on boundaries and non-Boussinesq effects. Convection driven by surface tension at a free surface is a distinct mechanism. An adverse temperature gradient supplies driving, but overcoming diffusion and viscosity requires a finite threshold.

Lay out a surveyed grid extending beyond the possible burial area into unaffected ground. Use closely spaced parallel traverses with measurements along each line; spacing should resolve a car-scale magnetic anomaly, with a finer grid over any candidate. For a shallow car, a pilot survey with roughly metre-scale spacing is a sensible starting point, refined according to anomaly width rather than treated as a universal prescription. Record position, time, sensor height, repeat readings and any nearby interference. Cross-lines and repeat stations check reproducibility. Maintain a constant sensor height on a nonmagnetic staff and remove magnetic items from the operator; map fences, gates, pipes, buildings and vehicles before interpreting an anomaly.

Operate a synchronized stationary base-station magnetometer in quiet ground while the rover surveys, or make frequent base returns if a second instrument is unavailable. A total-field magnetic anomaly is the corrected field magnitude minus a specified background:For a field-sized target, a local background estimated away from the car is often sufficient. A larger regional survey may subtract the International Geomagnetic Reference Field and an independently justified regional trend. Do not remove the car's broad anomaly by overfitting that trend.

Correct rover observations for time-varying geomagnetic field using the base record, for example $F_c(\mathbf{x},t)=F_r(\mathbf{x},t)-[F_b(t)-F_b(t_0)]$. Check instrument offsets and tie-line differences, reject disturbed or poor-quality readings, and allow for differing sensor heights. Preserve localized target signals when interpolating a contour map or comparing with a magnetic dipole model. There are no compulsory gravity-style free-air or Bouguer gravity anomaly reductions for this magnetic search.

Postpone surveying during a geomagnetic storm or rapid irregular magnetic variation, when base correction may be inadequate. Avoid periods of moving farm machinery or electrical interference, and recognize that strong permanent cultural interference or highly magnetic host rock may make this particular method unsuitable. Ordinary cloud cover or darkness does not prevent a magnetic survey.^[ref]

Strong geological magnetic anomalies generally occur in rocks containing abundant strongly magnetic iron oxides, especially magnetite and titanomagnetite. Many mafic rocks, including basalt and gabbro, and some ultramafic rocks have large signatures; magnetite-rich iron formations can be exceptionally strong, while serpentinization can create additional magnetite. Actual magnetic susceptibility and remanent magnetization, rather than the rock name alone, determine the response. Sedimentary and felsic rocks are often weaker but have important exceptions.

Magnetite, titanomagnetite and maghemite exhibit strong ferrimagnetism; some pyrrhotite is also strongly magnetic. Hematite is generally much weaker in induced magnetic susceptibility, although it can carry stable remanent magnetization. Quartz and calcite have very small, usually negative, susceptibilities, and many ordinary silicates have only weak paramagnetism. A steel car exhibits strong ferromagnetism and can therefore stand out against a weakly magnetic host, but its shape and pre-existing remanent magnetization complicate the signal.^[ref]