Applications to Lunar Remote Sensing - 3D Computer Vision: Efficient Methods and Applications - page 348

8.4.4 Discussion
Topographic mapping of planetary bodies is no end in itself but—especially
for the Moon—a precondition for a deeper understanding of the geophysical
processes that occurred in their early geologic history and formed their sur-
faces.
A novel classification scheme for 'monogenetic' lunar mare domes, which were
formed during a single eruption event, is introduced by Wöhler et al. ( 2006b ,
2007b ). It refines the classes 1-3 by Head and Gifford ( 1980 ) based on the morpho-
metric properties, i.e. the diameter, height, average flank slope, and volume of the
volcanic edifice measured by shape from shading analysis, as well as on the spectral
properties of the dome surface inferred from multispectral images of the Clemen-
tine spacecraft. This classification scheme suggests a division into four classes, three
of which are further subdivided into two subclasses, respectively (cf. Fig. 8.36 for
an overview). The morphologically more complex mare domes in the Marius Hills
region and near the crater Arago are assigned to two separate classes, while they
comprise one class in the scheme by Head and Gifford ( 1980 ). The morphomet-
ric properties inferred for the examined set of mare domes are used to estimate the
viscosity of the dome-forming magma, its effusion rate, and the duration of the ef-
fusion process, using a model originally developed by Wilson and Head ( 2003 )for
lunar highland domes. It is mentioned qualitatively by Weitz and Head ( 1999 ) that
the flank slopes of lunar domes increase with increasing lava viscosity and decreas-
ing lava effusion rate. These relations are confirmed quantitatively by the modelling
analyses of Wilson and Head ( 2003 ) and Wöhler et al. ( 2006b ). Similar analyses
are performed by Lena et al. ( 2009 ) for the volcanic edifices in the Marius Hills
region.
According to Wilson and Head ( 1996 , 2002 ), the magma was under pressure
and formed narrow, elongated crustal fractures, called dikes, during its ascent to
the surface. Based on a dike model introduced by Rubin ( 1993 ) and applied to lunar
highland domes by Wilson and Head ( 2003 ), the dimensions of the dikes that formed
lunar mare domes are estimated by Wöhler et al. ( 2007b ) along with the velocity at
which the magma ascended through them. By comparing the time scales of magma
ascent through a dike with the time scales on which heat was conducted from the
magma into the surrounding rock, evidence is found that the importance of 'magma
evolution' processes during ascent such as cooling and crystallisation increases with
increasing lava viscosity.
The study by Wöhler and Lena ( 2009 ) regards elongated lunar mare domes
with very low flank slopes of typically only some tenths of a degree. These domes
were not formed by lava effusion but possibly by an uplift of small parts of the
lunar crust by pressurised magma which had intruded between rock layers be-
low the surface. Such magmatic intrusions are termed 'laccoliths'. These 'candi-
date intrusive domes' (cf. the Valentine dome shown in Fig. 8.24 fasanexam-
ple) are examined in terms of the classical laccolith model introduced by Kerr
and Pollard ( 1998 ) in order to estimate the intrusion depth and the magma pres-
sure based on the morphometric properties inferred from shape from shading anal-