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Terrestrial analogues for investigating suspected monogenetic volcanic fields on Mars

Friday, June 22, 2012
Mark
Bishop

Volcanic shield fields are ubiquitous across planetary surfaces and have recently received significant attention in the geographic and geological mapping of Moon, Mars and Venus. In comparison, the spatial recognition and description of terrestrial shield fields and their association with cinder (scoria) cones and hydrovolcanic features  (e.g. maars) has been limited. Fields of low, diminutive shield shaped structures can occur as parasitic forms on larger composite edifices, for example, Kilauea in Hawaii, but can be commonplace also in many monogenetic volcanic landscapes such as the central Snake River Plain, USA, and the Newer Volcanic Province of southeastern Australia. For monogenetic provinces such as that in Australia, low shields may demonstrate the most significant output of magma and areal coverage relative to any other volcanic construct of Quaternary-to-late Neogene age. They also represent a landform in which the transport of lava can occur over many tens of kilometers through a complex array of tubes and channels.   Seminal studies on the shields of the Faroe Islands, Mauna Iki of Kilauea and Snake River Plain realized the necessity for a sub-category of shield volcano that was neither classic Hawaiian- or Icelandic-type. Terms of definition include lava cones, shield volcano of scutulum type and low shield. The term, low shield, is that which best describes the structures of the Newer Volcanic Province.                                                                          

In this paper, it is reported how the morphology of low shields for the Newer Volcanic Province has significant variation across the field, and that their organization is indicative of a shield field. Using Shuttle Radar Topography Mission (SRTM) DEM data and landscape analysis within a GIS, the metric of circularity was determined for successive natural breaks in slope to demonstrate the morphological variation of low shields and the manner in which volcanic landscapes may develop from discrete lava flows to expansive regional features. In this instance, morphometry demonstrates the role it has to play at identifying a spectrum of shield-like landforms. Although less obvious than either cinder (scoria) cones or maars, low shields have notable geomorphic involvement in the long-term evolution of planetary surfaces.

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