 |
| Titel |
Distribution of volcanism, topographic and geoid highs on terrestrial bodies: A comparison |
| VerfasserIn |
Stephanie C. Werner, Kevin Burke |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250047471
|
|
|
|
|
|
| Zusammenfassung |
| Here, we compare the surface records of volcanic activity and its relationship to the
topographical and geoidal expressions of the terrestrial planets and the Moon. Mantle
convection distorts internal interfaces, and results in dynamically driven topography, revealed
in the gravity field and geoid. Hot upwelling material and decompression melting in areas of
extension cause volcanism. Correlation between volcanically formed topography and
the geoid links internal processes and the surface, but the elastic behavior of the
lithosphere and on Earth plate tectonics make correlation more difficult back in
time.
Earth: Plate tectonics dominates igneous activity on the Earth and probably has done since
the moon-forming event. Decompression melting in active intra-continental rifts is next in
importance today but plate rotation-reconstructed volcanic non-plate margin eruption centers
(LIPs, kimberlites) and active hotspots are related to plumes from the edges of
two high density large low shear velocity provinces (LLSVPs) at the core-mantle
boundary that appear to have been stable for at least 500 Ma. Both LLSVPs correlate
with positive equatorial almost antipodal geoid anomalies. Geoid anomalies can
be observed on other planets for which mantle density distribution information is
lacking.
Mars resembles the Earth in revealing two almost antipodal and equatorial areoid anomalies.
Volcanic activity is distributed at the edges of the Syrtis Major centered anomaly, volcanic
provinces for which the activity ceased at least 1.5 Ga ago. The Tharsis volcanic
province is spatially correlated with the Tharsis centered anomaly where minor
volcanic activity has continued episodically until recently. Density anomaly models
for Mars averaged over the whole mantle suggest low densities below Tharsis,
which could indicate upwelling flow, but those models do not take into account
the possible existence of high density structures comparable to the LLSVPs on
Earth.
Venus: Topographic highs and aphroditoid highs coincide with volcanic centers and rift
systems, suggesting that the topographic expression of the volcanic provinces is
supported by dynamic upwelling (plumes) and shallow decompression melting below
rifts. No large antipodal geoid anomalies are observed. The surface record of the
volcanic activity on Venus indicates that it has occurred episodically over the entire
geological history. Assuming a (debated) maximum surface age of about 1 Ga,
mantle convection patterns on Venus have been stable over at least this period of
time.
Moon and Mercury: Volcanism after the crustal formation is mostly limited to the lunar
near-side mare units, and influences the selenoid strongly. An elliptic equatorial shape is
observed for the Moon. Preliminary observations at Mercury also suggest an equatorial
gravitational ellipticity. The distribution of volcanic activity appears more widespread than
previously thought.
Mars and the Earth show intriguing similarities and differences in geoid/volcanism links but
Venus, Mercury and the Moon do not. |
|
|
|
|
|
|