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The various origins proposed for intercrater plains on Mercury and the Moon lead to divergent thermal, tectonic, and bombardment histories. Relative ages of geologic units and structures place tight constraints on their origin and on the planet's geologic history. Crater statistics, lunar geologic map analysis, and geologic mapping of a quarter of Mercury's surface based on plains units dated relative to crater degradation classes were used to determine relative ages. Such studies provided the basis for deducing the origin of intercrater plains and their role in terrestrial planet evolution. Mercury's extensive intercrater plains span a range of ages contemporaneous with the period of heavy bombardment. Most intercrater plains predate scarp formation and the formation of the hilly and lineated terrain. The age of the latter is identical to that of its probable progenitor, the Caloris basin impact. Post-Caloris plains--smoother in texture, less extensive, and confined to crater depressions--formed as cratering waned and scarp formation progressed. This research indicates that mercurian intercrater plains are volcanic deposits interbedded with ballistically emplaced ejecta and reworked by basin secondaries and smaller impacts. A greater proportion of ejecta may comprise lunar intercrater plains. Neither the lunar nor mercurian intercrater surface is primordial because each preserves pre-plains crateriforms. Ancient volcanism on Mercury is evidenced by widespread plains distribution, structurally controlled deposition, embayment of craters and basins, associated (but tentative) volcanic landforms, losses of small craters, and uncorrelated plains and crater coverage. The limited range of mercurian ejecta reduces the resurfacing potential relative to that of lunar craters. Crater densities are affected by intercrater plains emplacement, additions of secondaries, ancient basin impacts, and target physical properties. "One-plate" thermo-tectonic models best explain the geologic characteristics recognized in this study. Thermal expansion during core formation causes global extension and widespread volcanic extrusions; subsequent cooling and radial contraction form compressional scarps. Younger plains-forming materials issue from magma reservoirs in subsurface tensional zones tapped by impact fractures. The age and stress environment of these volcanic plains suggest a source greater than 40 km depth and a composition different from that of the intercrater plains.

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Despite its ubiquity in planetary science, analogue-based reasoning largely has remained unbounded by guidelines of use. Establishing analogical guidelines and putting them to the test is the main aim of the thesis. Towards this end, I discuss the philosophical foundations of analogical reasoning in planetary geomorphology and posit rules of use that facilitate the evaluation of analogical hypotheses. Subsequently, I present four hypotheses concerning aeolian, fluvial and periglacial processes on Mars. Each of these hypotheses is evaluated in terms of the analogical rules presented. The fourth hypothesis is original to this thesis and suggests that a periglacial landscape comprising pingos and small-scale polygonal ground exists in an impact crater located in northwest Utopia Planitia.

A research report submitted In partial fulfilment for the degree Master of Science (Geographical Information Systems & Remote Sensing). to the School of Geography, Archaeology & Environmental Studies, University of the Witwatersrand, Johannesburg , July 2017 / The nature of urban development experienced by mining towns across the world has been a subject of concern among urban planners because of its transitory nature. Most times mining towns develop gloriously into booming urban centres that create employment, generate wealth and satisfaction. All these fades into oblivion as soon as the mines get depleted. Mining towns often go through a number of urban processes which have been considered an expression of ‘infrastructural violence’ especially in the earlier stage of urban growth, and continually persists throughout the town’s life span. This research sought to reconstruct the history of urban development in the mining town of Virginia, Free State, and to quantify the manifestations of infrastructural violence throughout its timeline using GIS and remote sensing. Hence, land use and land cover maps were produced from aerial photographs, topographical maps and Landsat images through manual on-screen digitizing and classification using supervised support vector machine algorithms. Land use change detection analysis was conducted on the produced images using the cross classification and tabulation tool of QGIS 2.18.4 and the post classification tool of ENVI 5.3. Landscape metrics were employed to calculate the dimensions of growth and change experienced by all the land use classes during the timeline under study. Results obtained from this study confirmed the thoughts and findings of several theories vis a vis the nature of mining towns. Results reveal a rapid growth in the urban formal land use class up until 1995 with urban expansion and sprawl happening in the years between 1986 and 1995 with metrics of CA, NP and ED multiplying to twice their initial values ten years earlier. The urban informal land use class also experienced its subtle growth throughout the timeline of the study with its own urban expansion also happening between 1986 and 1995 with double increase in CA, NP and ED metric values. However, unlike the formal class that experienced decline after this period of urban expansion, the informal class continued to experience growth up until the end of the study period. Infrastructural violence was measured using the fractal dimension index (AWMPFD) of the landscape metrics for the formal and informal LU class. The results reveal continuous fragmentation throughout the period of study but with higher values in the years in which urban development started. / LG2018

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