Björn Holger Heyn

Researcher - Centre for planetary habitability

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Email b.h.heyn@geo.uio.no

Room 2.329

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Visiting address Sem Sælands vei 2A ZEB-bygget 0371 Oslo

Postal address Postboks 1028 Blindern 0316 Oslo

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Academic Interests:

I am a geodynamicist with background in seismology and a solid understanding of geochemistry. I use the finite element code ASPECT to develop numerical models of mantle convection, with a special focus on the lower mantle and mantle upwellings (plumes) from their source at the core-mantle boundary (CMB) to their surface expressions. have done research on the dynamics of Large Low Shear Velocity Provinces (LLSVPs), plume formation, plume-lithosphere interaction and core-mantle boundary topography.

LLSVP dynamics: what is the origin and evolution of thermochemical heterogeneities in the lower mantle? How do they interact with and impact mantle flow?
Plume formation: what triggers the formation of mantle plumes? What is the role of subduction and the LLSVPs? Is there a periodicity of the process?
Plume-lithosphere interaction: How do plumes interact with surface plates? What is the effect of plumes on surface heat flux, lithosphere thickness, and melting?
Core-mantle boundary topography: How do internal processes like plume formation deflect the core-mantle boundary? Can we measure this and infer details about the state and dynamics of the lower mantle? How to model this topography accurately?

Teaching:

Guest lecturer AGx51 - UNIS Arctic Tectonics and Volcanism
Guest lecturer GEO-DEEP 9100 Planetary Physics and Global Tectonics

Outreach and in media:

NOR-R-AM blog Data Aquisition in the Arctic September 30, 2018
Research Highlight in Nature Reviews Earth and Environment on Heyn et al. (2020, JGR): The Rise and Fall of mantle plumes by Matthew Gleeson
Interview with forskning.no Forskere har undersøkt to enorme, mystiske strukturer i jordens indre March 28, 2022
CEED's Research blog Revealing “invisible” plume tracks beneath continents April 6, 2022

Former projects involved:

MAGPIE - Magnetotelluric Analysis for Greenland and Postglacial Isostatic Evolution
3D Earth - Greenland, funded by the European Space Agency (ESA)

Tags: Geodynamics, Mantle Convection, Geophysics, Seismology, Numerical Modeling, Numerical simulations

Heyn, Björn Holger & Conrad, Clinton Phillips (2022). On the Relation Between Basal Erosion of the Lithosphere and Surface Heat Flux for Continental Plume Tracks . Geophysical Research Letters. ISSN 0094-8276. 49(7). doi: 10.1029/2022GL098003. Full text in Research Archive Show summary
While hotspot tracks beneath thin oceanic lithosphere are visible as volcanic island chains, the plume-lithosphere interaction for thick continental or cratonic lithosphere often remains hidden due to the lack of volcanism. To identify plume tracks with missing volcanism, we characterize the amplitude and timing of surface heat flux anomalies following a plume-lithosphere interaction using mantle convection models. Our numerical results confirm an analytical relationship in which surface heat flux increases with the extent of lithosphere thinning, which is primarily controlled by the viscosity structure of the lower lithosphere and the asthenosphere. We find that lithosphere thinning is greatest when the plate is above the plume conduit, while the maximum heat flux anomaly occurs about 40-140 Myr later. Therefore, younger continental and cratonic plume tracks can be identified by observed lithosphere thinning, and older tracks by an increased surface heat flux, even if they lack extrusive magmatism.
Heyn, Björn Holger; Conrad, Clinton Phillips & Trønnes, Reidar G (2020). Core-mantle boundary topography and its relation to the viscosity structure of the lowermost mantle . Earth and Planetary Science Letters. ISSN 0012-821X. 543. doi: 10.1016/j.epsl.2020.116358. Full text in Research Archive Show summary
Two large areas of anomalously low seismic velocities are visible in all tomographic models of the lowermost mantle. Depending on the density structure of these Large Low Shear Velocity Provinces (LLSVPs), the core-mantle boundary (CMB) will deform upwards or downwards due to isostatic and dynamic topography, the latter being sensitive to the viscosity structure of the lowermost mantle. Heterogeneities in the viscosity structure, although difficult to constrain, might be especially important if the LLSVPs are thermochemical piles with elevated intrinsic viscosity as suggested by mineral physics. Based on numerical models, we identify a short-wavelength (about 80-120 km wide, up to a few km deep) topographic depression that forms around the pile edges if the pile is more viscous than the surrounding mantle. The depression forms when a wedge of thermal boundary layer material becomes compressed against the viscous pile, and is enhanced by relative uplift of the CMB beneath the pile by plumes rising above it. The depth and asymmetry of the depression constrain the magnitude of the viscosity contrast between pile and the surrounding mantle. Furthermore, (periodic) plume initiation and pile collapse at the pile margin systematically modify the characteristic depression, with a maximum in asymmetry and depth at the time of plume initiation. Core-reflected waves or scattered energy may be used to detect this topographic signature of stiff thermochemical piles at the base of the mantle.
Heyn, Björn Holger; Conrad, Clinton Phillips & Trønnes, Reidar G (2020). How Thermochemical Piles Can (Periodically) Generate Plumes at Their Edges . Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 125(6). doi: 10.1029/2019JB018726. Full text in Research Archive Show summary
Deep-rooted mantle plumes are thought to originate from the margins of the Large Low Shear Velocity Provinces (LLSVPs) at the base of the mantle. Visible in seismic tomography, the LLSVPs are usually interpreted to be intrinsically dense thermochemical piles in numerical models. Although piles deflect lateral mantle flow upward at their edges, the mechanism for localized plume formation is still not well understood. In this study, we develop numerical models that show plumes rising from the margin of a dense thermochemical pile, temporarily increasing its local thickness until material at the pile top cools and the pile starts to collapse back toward the core-mantle boundary (CMB). This causes dense pile material to spread laterally along the CMB, locally thickening the lower thermal boundary layer on the CMB next to the pile, and initiating a new plume. The resulting plume cycle is reflected in both the thickness and lateral motion of the local pile margin within a few hundred km of the pile edge, while the overall thickness of the pile is not affected. The period of plume generation is mainly controlled by the rate at which slab material is transported to the CMB, and thus depends on the plate velocity and the sinking rate of slabs in the lower mantle. A pile collapse, with plumes forming along the edges of the pile's radially extending corner, may, for example, explain the observed clustering of Large Igneous Provinces (LIPs) in the southeastern corner of the African LLSVP around 95–155 Ma.
Trønnes, Reidar G; Baron, Marzena Anna; Eigenmann, Katarina R.; Guren, Marthe Grønlie; Heyn, Björn Holger & Løken, Andreas [Show all 7 contributors for this article] (2019). Core formation, mantle differentiation and core-mantle interaction within Earth and the terrestrial planets. . Tectonophysics. ISSN 0040-1951. doi: 10.1016/j.tecto.2018.10.021. Full text in Research Archive
Heyn, Björn Holger; Conrad, Clinton Phillips & Trønnes, Reidar G (2018). Stabilizing effect of compositional viscosity contrasts on thermochemical piles. Geophysical Research Letters. ISSN 0094-8276. 45(15), p. 7523–7532. doi: 10.1029/2018GL078799. Full text in Research Archive Show summary
The large low shear velocity provinces (LLSVPs) observed in the lowermost mantle are widely accepted as chemically distinct thermochemical 'piles', but their origin and long-term evolution remain poorly understood. The survival time and shape of the LLSVPs are thought to be mainly controlled by their compositional density, while their viscosity has beeen considered less important. Based on recent constraints on chemical reactions between mantle and core, a more complex viscosity structure of the lowermost mantle, possibly including high viscosity thermochemical pile material, seems reasonable. In this study, we use numerical models to identify a trade-off between compositional viscosity and density contrasts required for long-term stability of thermochemical piles, which permits lower-density and higher-viscosity piles. Moreover, our results indicate more restrictive stability conditions during periods of strong deformation-induced entrainment, e.g. during initial pile formation, which suggests long-term pile survival.
Reiss, Anne-Sophie; Thomas, Christine; van Driel, Jac & Heyn, Björn Holger (2017). A hot midmantle anomaly in the area of the Indian Ocean Geoid Low. Geophysical Research Letters. ISSN 0094-8276. 44(13), p. 6702–6711. doi: 10.1002/2017GL073440.

View all works in Cristin

Thomas, Christine & Heyn, Björn Holger (2024). Imaging deep subducted lithosphere beneath the Indian Ocean with seismic source array recordings.
Heyn, Björn Holger; Shephard, Grace & Conrad, Clinton Phillips (2024). Prolonged multi-phase volcanism in the Arctic induced by plume-lithosphere interaction.
Heyn, Björn Holger & Conrad, Clinton Phillips (2023). Development and implications of a free base for numerical models.
Heyn, Björn Holger; Conrad, Clinton Phillips & Shephard, Grace (2023). Plume-lithosphere interaction and continental plume tracks.
Shephard, Grace; Heyn, Björn Holger & Conrad, Clinton Phillips (2023). Prolonged multi-phase magmatism due to plume-lithosphere interaction as applied to the High Arctic Large Igneous Province.
Heyn, Björn Holger; Shephard, Grace & Conrad, Clinton Phillips (2023). Locally amplified plume-lithosphere interaction and multiple melting events for 2-phase flow models.
Heyn, Björn Holger; Shephard, Grace & Conrad, Clinton Phillips (2023). Amplification of sub-lithospheric dynamics by melt migration during plume-lithosphere interaction.
Shephard, Grace; Heyn, Björn Holger & Conrad, Clinton Phillips (2023). Large-scale volcanism at the top of the world; plume and melt modelling of the High Arctic Large Igneous Province (HALIP).
Heyn, Björn Holger (2022). Forskere har undersøkt to enorme, mystiske strukturer i jordens indre. [Newspaper]. https://www.forskning.no/geologi/forskere-har-undersokt-to-e.
Heyn, Björn Holger & Shephard, Grace (2022). Revealing “invisible” plume tracks beneath continents.
Heyn, Björn Holger & Conrad, Clinton Phillips (2022). Basal erosion and surface heat flux anomalies associated with plume-lithosphere interaction beneath continents.
Rolf, Tobias; Crameri, Fabio; Heyn, Björn Holger & Thielmann, Marcel (2022). Testing a (quasi-)free base for modelling core-mantle boundary topography.
Shephard, Grace; Gaina, Carmen; Heyn, Björn Holger; Conrad, Clinton Phillips; Anfinson, Owen & Schaeffer, Andrew [Show all 7 contributors for this article] (2022). Exploring potential lower mantle structures and interactions for the origins of HALIP.
Heyn, Björn Holger & Conrad, Clinton Phillips (2021). Plume-induced heat flux anomalies and the associated thinning of the continental lithosphere.
Heyn, Björn Holger; Conrad, Clinton Phillips & Trønnes, Reidar G (2020). How thermochemical piles initiate plumes at their edges. European Geosci. Union, Gen. Assembly, Geophys. Res. Abstr..
Heyn, Björn Holger; Conrad, Clinton Phillips & Selway, Kate (2020). Numerical constraints on heat flux variations and lithospheric thinning associated with passage of the Iceland plume beneath Greenland.
Selway, Kate; Conrad, Clinton Phillips; Ramirez, Florence; Karlsson, Nanna B; Weerdesteijn, Maaike Francine Maria & Heyn, Björn Holger (2020). How magnetotellurics can aid cryosphere studies: mantle rheology, GIA, surface heat flow, and basal melting.
Heyn, Björn Holger; Conrad, Clinton Phillips & Trønnes, Reidar G (2020). How thermochemical piles initiate plumes at their edges.
Conrad, Clinton Phillips; Domeier, Mathew; Selway, Kate & Heyn, Björn Holger (2020). A link between seamount volcanism and thermochemical piles in the deepest mantle.
Heyn, Björn Holger; Conrad, Clinton Phillips & Trønnes, Reidar G (2020). How thermochemical piles initiate plumes at their edges .
Heyn, Björn Holger; Conrad, Clinton Phillips & Trønnes, Reidar G (2019). What core-mantle boundary topography can tell us about plume locations and the viscosity and density structure of thermochemical piles. European Geosci. Union, Gen. Assembly, Geophys. Res. Abstr..
Heyn, Björn Holger; Conrad, Clinton Phillips & Trønnes, Reidar G (2019). Core-mantle boundary topography and its relation to lowermost mantle viscosity structure. Ada Lovelace Workshop on Modelling Mantle and Lithosphere Dynamics. Abstr..
Heyn, Björn Holger; Conrad, Clinton Phillips & Trønnes, Reidar G (2019). Periodic plume generation at the edges of thermochemical piles. European Geosci. Union, Gen. Assembly, Geophys. Res. Abstr..
Conrad, Clinton Phillips; Domeier, Mathew; Selway, Kate & Heyn, Björn Holger (2019). A link between seamount volcanism and thermochemical piles in the deepest mantle.
Heyn, Björn Holger; Conrad, Clinton Phillips & Trønnes, Reidar G (2019). Periodic plume generation at the edges of thermochemical piles.
Heyn, Björn Holger; Conrad, Clinton Phillips & Trønnes, Reidar G (2019). Core-mantle boundary topography and its relation to lowermost mantle viscosity structure.
Heyn, Björn Holger; Conrad, Clinton Phillips & Trønnes, Reidar G (2019). What core-mantle boundary topography can tell us about plume locations and the viscosity and density structure of thermochemical piles.
Heyn, Björn Holger; Conrad, Clinton Phillips & Trønnes, Reidar G (2019). Linking surface volcanism and deep Earth: Piles, plumes, and dynamic topography.
Heyn, Björn Holger; Conrad, Clinton Phillips & Trønnes, Reidar G (2018). Stabilization of thermochemical piles by compositional viscosity contrasts.
Heyn, Björn Holger; Conrad, Clinton Phillips & Trønnes, Reidar G (2018). Stabilization of thermochemical piles by compositional viscosity contrasts. EGU Gen. Assembly, EGU2018-12950.
Heyn, Björn Holger; Conrad, Clinton Phillips & Trønnes, Reidar G (2017). Stabilizing effect of a chemical viscosity contrast on LLSVP structures Abstr., Gordon Res. Conf. on Chemical and dynamical evolution of Earth's deep interior, from formation to today. Mount Holyoke College, South Hadley, MA.
Heyn, Björn Holger & Conrad, Clinton Phillips (2020). Geodynamics of Earth’s Large Low Shear Velocity Provinces Interaction with mantle flow, plume initiation, and core-mantle boundary deformation. Universitetet i Oslo. ISSN 1501-7710. Show summary
Our planet’s interior is actively convecting like boiling water in a pot, although on significantly larger length and time scales. In some locations, such as Hawaii and Iceland, one consequence of this convection is strong, long-lived volcanism that eventually creates island chains. But where does the erupted material come from, why is the volcano located at this specific spot, and what are the mechanisms to trigger this volcanism? To understand the origins of this Hawaiian-type volcanism, we have to dive deep into the interior of Earth, where the driving forces of convection are located. This doctoral study uses numerical simulations to unravel how continent-sized piles of dense and potentially stiff material, residing about 2900 km beneath our feet, affect the formation of strong upwelling “plumes” that are thought to be associated with Hawaiian-type volcanism. Due to internal deformation, such piles periodically perturb a layer of hot material surrounding them, causing some material to rise and eventually erupt into volcanism. Moreover, this triggering mechanism causes a characteristic depression on the core-mantle boundary that may be used to constrain the properties of the deep Earth, and also locate newly emerging plumes before they erupt to the surface to produce Hawaiian-type volcanoes.
Heyn, Björn Holger (2020). Geodynamics of Earth's Large Low Shear Velocity Provinces Interaction with mantle flow, plume formation, and core-mantle boundary deformation. Unipub forlag. ISSN 1501-7710. Full text in Research Archive Show summary
Based on evidence from the geochemistry of ocean island volcanism, we know that the Earth’s mantle must be heterogeneous on various scales, despite active convection for billions of years. Seismic tomography has shown that there are two continent-sized regions of anomalously low seismic velocities at the base of the mantle, the so-called Large Low Shear Velocity Provinces (LLSVPs), which likely represent piles of chemical heterogeneities resulting from magma ocean crystallisation at the beginning of Earth’s history. Large-scale upwellings, so-called mantle plumes, and the associated hotspot volcanism seem to cluster around these piles, which are presumably dense and potentially viscous due to their composition. This thesis explores the importance of viscosity contrasts on the interaction between mantle flow, mantle plumes and dense thermochemical piles. It demonstrates the importance of viscosity for entrainment of pile material by plumes, and shows how piles interact with mantle flow to periodically generate plumes around their margins. This interaction produces short-scale core-mantle boundary topography, which, if detected, should constrain the nature and properties of LLSVPs.