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PHYS2403 Simulation Lab

Experiment 9: Isostasy and Crustal Thickness

Isostasy describes the state of gravitational equilibrium between the Earth's lithosphere and mantle, which determines why lighter continental crust floats high above denser mantle rocks. Use this simulation to explore mountain root mechanisms (Airy vs Pratt vs Flexural), examine corresponding gravity anomaly profiles, and trace active post-glacial rebound curves.

Isostatic Parameters

Compensation Model
Mountain Height (H)2000 m
Crust Density (ρ_crust)2750 kg/m³
Normal crust thickness (hc0)35 km
Post-Glacial Loading

Subsurface Crustal StructureModel: Airy

H = 2.0kmr = 10.0kmCrust (Compensated)Mantle (ρ = 3300 kg/m³)

Gravity Profile (mGal)

+100-100
FA: 152.0 mGalBoug: -159.3 mGal

Glacial Uplift Rebound

00.0km025k yrs
Airy Isostasy Model

Supports topography using a low-density crustal root. The root depth rr is proportional to mountain height HH:

r=Hρcρm−ρcr = H \frac{\rho_c}{\rho_m - \rho_c}
Pratt Isostasy Model

Supports topography by varying lateral density ρ(x)\rho(x) at constant Moho depth DD:

ρ(x)(D+H(x))=constant\rho(x)(D + H(x)) = \text{constant}
Isostatic Rebound Uplift

Uplift profile after removing a glacial ice load, decaying exponentially over relaxation time τ\tau:

w(t)=w0e−t/τw(t) = w_0 e^{-t/\tau}