domenica 15 giugno 2014

Rümker volcanic complex

Rümker domes (termed Rümker 1-8)

by Mike Wirths

by Mike Wirths

by Jim Phillips

Dome
Longitude
Latitude
Diameter [km]
Heigth [m]
Slope[°]
Rümker 1
Rümker 2
Rümker 3
Rümker 4
Rümker 5
-58.80
-58.00
-58.30
-58.00
-57.30
41.50
41.30
40.30
40.10
41.00
8.4 ± 0.5
9.1 ± 0.5
9.1 ± 0.5
7.3 ± 0.5
5.5 ± 0.5
200 ± 20
130 ± 15
240 ± 25
170 ± 20
70 ± 10
2.7 ± 0.2
1.6 ± 0.2
3.0 ± 0.2
2.7 ± 0.2
1.5 ± 0.2
Rümker 6
-58.70
40.60
6.9 ± 0.5
100 ± 10
1.7 ± 0.2


Rümker domes (LRO WAC imagey).
Rümker plateau is composed of a series of overlapping domes, lava flows and to a ring surrounding the central portion. The examined domes on the Rümker plateau are typical mare domes morphometrically similar to the class B1 domes, in the Hortensius/Milichius/T. Mayer region, denoting steep flank slopes >2° (Rümker 1, 3 and 4), and B2, representing domes with lower slopes.
Rheologic modelling results confirm that the domes were produced by low effusion rates, possibly during the terminal phases of the eruptions emplacing the plateau. The significant differences among the lava viscosities inferred for the domes (from 104 to 106 Pa s) is not attributed to compositional effects due to the observed spectral homogeneity but are more likely caused by different lava eruption temperatures and degrees of crystallization.
The magma reservoirs feeding the domes-forming eruption were located just below the lunar crust (inferred dike lengths between 25 km for Rümker 5 to 89 km for Rümker 4) when a crustal thickness of ~50 km is assumed for the Rümker region. Further two domes have been identified in WAC imagery (R7-R8). The lower domes termed R2, R6 and R8 (with corresponding flank slopes of 1.7°-1.8°) belong to subclass B2. The very small domes R5 and R7 (diameters < 6km and corresponding flank slopes of 1.5°-1.9°) are similar to M7, encountered in Mare Insularum near Tobias Mayer and belong to subclass E2, while the steeper domes R1, R3, and R4 (with flank slopes of 2.7°-3.0°) are of subclass B1. If the effusion process continues over a long period of time, steep flank slopes and high volumes may occur (class B1), while short periods of effusion result in shallower edifices of lower volume (class B2). The heights of the domes R7 and R8, previously not measured, are determined to 97 m and 135 m.