Explore crustal structure with practical field and classroom data. Compare methods and validate key assumptions. Save clear result sheets for research, revision, and reports.
| Method | Example Inputs | Example Output |
|---|---|---|
| Airy Isostasy | h = 2.5 km, T0 = 35 km, ρc = 2800, ρm = 3300, C = 1 | Estimated crustal thickness = 49.000 km |
| Seismic Travel Time | t = 10 s, Vp = 6.5 km/s, θ = 0°, e = 0.8 km | Estimated crustal thickness = 33.300 km |
| Gravity Slab Approximation | Δg = -120 mGal, Δρ = 400 kg/m³, T0 = 35 km | Estimated crustal thickness = 42.156 km |
T = T0 + C × [h × ρc / (ρm - ρc)]
This method estimates crustal thickening from topography and density contrast. It is useful for mountain belts and compensated terrains.
T = [(Vp × t × cos θ) / 2] + e
This method uses two-way travel time to the Moho. It assumes an average crustal P-wave velocity and a simple ray path.
ΔT = |Δg| / (2πGΔρ)
T = T0 ± ΔT
This method converts Bouguer anomaly into an equivalent thickness change. It is a simplified first-pass model for thickening or thinning.
Crustal thickness is the vertical distance from the land or seafloor surface to the Mohorovičić discontinuity. Geophysicists often call this boundary the Moho. It marks the transition from crustal rocks to mantle rocks. Continental crust is usually thicker than oceanic crust. Mountain belts often show the largest values. Rift zones and ocean basins often show smaller values.
Crustal thickness changes because plates collide, stretch, cool, erode, and load sediment. Compression can build deep crustal roots. Extension can thin the crust. Volcanic addition can also modify thickness. Sedimentary basins may hide major lateral changes. These changes matter for tectonic models, basin studies, heat flow estimates, and lithospheric strength.
No single method is perfect. Airy isostasy is fast and useful when topography and density assumptions are available. Seismic travel time links thickness directly to wave propagation and Moho reflections. Gravity methods convert Bouguer anomaly into an equivalent thickness signal. Each method responds to different assumptions. Comparing them helps you test plausibility.
Always treat the output as model-based. Density values, velocity averages, compensation state, and anomaly filtering strongly affect the estimate. A good workflow is to compare map patterns, geology, topography, and seismic constraints together. If two methods agree, confidence often improves. If they disagree, the mismatch may reveal real structure, poor assumptions, or data quality issues.
This calculator is useful for tectonics assignments, geophysics labs, field preparation, and quick screening studies. It supports crustal thickness estimation, Moho depth discussions, mountain root analysis, and gravity-based comparison. It also helps students understand how crust density, mantle density, seismic velocity, and Bouguer anomaly control geophysical interpretation.
The Moho is the boundary between Earth’s crust and mantle. Crustal thickness is commonly measured from the surface down to this boundary.
Airy isostasy is often useful for mountain belts because elevation can reflect deep crustal roots. Still, seismic data usually gives stronger direct constraints.
Yes. Negative elevation can represent low topography or below-sea-level surfaces. In the Airy model, that can reduce the estimated crustal thickness.
Density contrast controls how much mass difference is needed to balance topography or gravity anomaly. Small contrast can produce larger thickness changes.
No. It is a simplified average-velocity estimate. Real crust contains velocity layering, anisotropy, dipping interfaces, and complex ray paths.
In this simple slab model, a negative Bouguer anomaly often suggests thicker or less dense crust relative to the reference model.
Yes, but assumptions must fit oceanic settings. Use realistic densities, velocities, and reference thickness values for marine crust.
It is better to compare results with seismic profiles, mapped geology, topography, and regional gravity interpretation before drawing conclusions.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.