 |
| Titel |
Prediction of Dyke Propagation using the Minimum Potential Energy Principle |
| VerfasserIn |
Elías Heimisson, Andrew Hooper, Freysteinn Sigmundsson |
| Konferenz |
EGU General Assembly 2015
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250111070
|
| Publikation (Nr.) |
 EGU/EGU2015-11135.pdf |
|
|
|
|
|
| Zusammenfassung |
| An important aspect of eruption forecasting is the prediction and monitoring of dyke
propagation. Eruptions occur where dykes propagate to the surface, with lava flows causing a
major threat. When such eruption occur under ice, as is common in Iceland, they become
explosive and often cause hazardous and destructive floods. Dykes have also been known to
trigger explosive eruption when hot basaltic magma comes in contact with more developed
volatile saturated magma. Such explosive eruptions pose a danger to both lives and
property.
At divergent plate boundaries new crust is formed primarily by dyke injections. These
injections usually grow laterally away from a central volcano. Lateral growth of a dyke is
expected to follow the minimum potential energy principle. Assuming a closed system, a
dyke will tend to be emplaced such that it minimizes the total potential energy, ÎT, given
by:
ÎT = Îs + Îg
(1)
where Îs is the strain potential and Îg the gravitational energy potential. Assuming that
the elastic medium behaves linearly the strain potential can be calculated by numerically
integrating the strain energy density over a large volume. If the dyke is assumed to be
propagating at a constant depth with respect to sea level the gravitational potential energy can
be turned into a two dimensional integral. We do this by integrating the predicted vertical
displacements multiplied by the local topographic load above a reference surface and the
acceleration of gravity.
We approximate strain and stress due to plate movements and then consider strain
changes induced by the dyke formation. Opening of a dyke is energetically favourable when
it releases strain energy built up at a divergent plate boundary, but once deviatoric stress in the
crust adjacent to a segment is released it becomes favourable to propagate laterally. Dyke
formation is associated with uplift on their flanks; the lower the topographic load over the
flanks, the less energy it costs. For any given location on a volcano, the strike of a new dyke
segment will influence the strain and gravitational potential energy change in a different
way.
This type of model was applied to the more than 45 km long dyke formed in the
Bárðarbunga volcanic system in Iceland in a rifting event in August 2014. Large
observed changes in strike can be explained mostly by interplay of gravitational
effects of topography and plate boundary strain. The model minimizing the total
potential energy explains this propagation path. Our results suggest that by applying
the total minimum potential energy principle we can forecast dyke propagation. |
|
|
|
|
|
|