Exploring the Role of Intrusive Magmatism on Topographic Form

Interpretations of long-lived volcanic systems require an understanding of both current and historic states of the underlying magma plumbing system. These are typically completed through geologic and geophysical surveys, which are not available for most volcanoes on Earth. However, topographic form of volcanic regions is a globally-available resource that could provide complementary quantitative information on time-integrated volcanic phenomenology. Despite magmatically derived landforms encompassing ~10% of the Earth's terrestrial surface, topography and volcanic processes are generally studied independently. Topographic signatures of regional-scale magmatism over long timescales remain unexplored.

Here, we study the relationship between magmatic intrusive bodies and topography with a numerical model that combines standard models for surface uplift from pressurized magma chambers. We subdivide intrusions into two classes based on intrusion radius (R) and depth (D) - using the so-called Mogi model (inflation point source within an elastic half-space) for deep (R < D) intrusions and a thin-plate flexure model for shallow (R > D). We randomly determine intrusion XY locations using a Poisson distribution, and explore the effects of various intrusions on surface topography by randomly-sampling R and D from distributions constrained by global observations and linear elastic models. Our model tracks the crustal thickening associated with many generations of intrusions, as well as the evolving surface topography.

Topographic signatures of intrusions can be classified according to magmatic flux and the distribution of intrusion depths. The amplitude of topography from individual intrusions decreases as intrusion depth increases, while the lateral wavelength increases. By combining the spatiotemporal variation in crustal thickening with the surface topographic power spectra, we can map the amount of mantle-derived magma and depth distribution of intrusions to surface form.