two or possibly three ice-filled calderas, each of which is about wide. The calderas are apart and located at the Prahl Crags, Britt Peak and potentially Kohler Dome localities. Additionally the Prahl Crags – remnants of the former caldera rim – are found south, Gawne Nunatak west, Edwards Spur northeast and the Moulton Icefalls on the northern side of the mountain. The total volume of the complex is about , comparable to that of Mount Shasta in the Cascade Range, and is one of the largest volcanoes in the Flood Range and Ames Range. Only the western part of the Mount Moulton emerges from the ice. Volcanic rocks found at Mount Moulton include pantellerite, phonolite and trachyte; phenocryst phases found in the pantellerite include aenigmatite, anorthoclase, fayalite, hedenbergite, ilmenite and quartz. Blue ice field A blue ice field has formed within the caldera of Mount Moulton behind the Prahl Crags, and contains ice almost 500,000 years old. It is the oldest dated ice in West Antarctica and much older than ice found elsewhere in West Antarctic ice cores. Such blue ice fields like those found at Mount Moulton form when glaciers run into an obstacle – in this case the Prahl Crags – and part of the ice starts moving vertically as it undergoes ablation processes like sublimation. In the case of Mount Moulton, this outcrop of ice is about long. The ice has been used to reconstruct past climate states in West Antarctica, including the beginning and end of the last interglacial, and shows evidence that the West Antarctic Ice Sheet collapsed during that interglacial. In addition, recognizable tephra layers are found in this ice and appear to originate from explosive eruptions of volcanoes such as Mount Berlin, Mount Takahe and Mount Waesche, although some may come from parasitic vents of Mount Berlin and Mount Moulton. These tephra layers at Mount Moulton crop out in parallel layers and geochemical traits indicate an origin at Mount Berlin although some layers may have been erupted from mafic volcanoes at Mount Moulton and Mount Berlin. Furthermore, the appearance of the deposits indicates that the eruptions of Mount Berlin were highly explosive. Most likely they eventually fell onto the ice of Mount Moulton, were incorporated in it and then transported downward to the blue ice field. See also List of volcanoes in Antarctica References Sources Further reading Flood Range Polygenetic shield volcanoes Volcanoes