Lansberg D domes

Lansberg D  domes (termed La 1-3)

by Mike Wirths

Dome	Longitude	Latitude	Diameter [km]	Heigth [m]	Slope[°]
Lansberg 1 Lansberg 2 Lansberg 3	-29.79° -30.23° -30.09°	-03.54° -04.02° -04.49°	20x16 ± 0.5 25x19 ± 0.5 19x15 ± 0.5	120 ± 15  80 ± 10 120 ± 15	0.68 ± 0.1 0.4 ± 0.1 0.77 ± 0.1

The three domes near Lansberg D are of strongly elongated shape and La1 and La2 display straight rilles traversing their surfaces, which are likely of tensional origin, due to a possible intrusive origin. The heights of La1-La3 correspond to 120 m, 80 m and 120 m, respectively, resulting in average flank slopes of 0.68°, 0.40° and and 0.77°. It is unlikely that they are kipukas as no spectral contrast is apparent between them and the surrounding surface. Regarding the morphometric properties and modelling results, La2 and La3 are typical representative of class In1 and In2, respectively. The steeper dome La3 indicates that laccolith formation proceeded until the stage characterized by flexure of the overburden, while La2 and La1 are characterized by rilles likely due to tensional stresses, consistent with laccolith formation. Hence the magma accumulating beneath the surface produced not only an upbowing of the surface rock layers but also failures in the rock strata (fracturing).