A區和C區均以特大尺度冰川線理(MSGLs)為主要冰下地貌。如圖2.2和圖2.4所示，在高分辨率hillshade柵格上可以清楚地看到“平行形成的脊溝特征”(Jakobson et al.， 2012)。MSGLs可以定義為“長度在10,000到100,000米之間的線性形式，這是最容易從航空照片或衛星圖像中觀察到的”(Clark, 1993)。這些小冰柱據說是由德拉姆斯冰柱形成的，因為它們更大更長，而且它們為曾經有快速冰流的地區提供了證據。關于MSGLs的形成提出了幾種理論，但由于冰動力學的復雜性，沒有一種理論被廣泛接受。Shaw等人提出了MSGLs是由湍流融水侵蝕形成的觀點，然而，現代觀測表明，冰原的河床是在沒有融水泛濫的情況下形成的。另一種理論是“床層變形模型”，該模型認為，由于上覆冰對沉積物施加剪應力，使軟弱的沉積物發生變形，從而形成了MSGLs。但這一理論不能解釋drumlins和MSGLs形成的模式現象。不穩定性理論是最廣泛接受的，雖然它不能解釋所有的形成方面，是由印度德馬什在1998年提出的。它指出，冰和冰下沉積物的耦合流動可能具有內在的不穩定性，因此冰磧表面可能會自發地形成波浪，并以特定的波長生長。這意味著，具有不同物理性質的材料層容易發生不穩定性(不穩定性被稱為在一個系統中，當小的不規則自發地生長，產生規則的模式，在這種情況下，MSGLs)。這一理論還沒有得到足夠的研究來得出是否這就是MSGLs形成的結論。這些理論，加上其他的，是激烈的爭論，所以MSGL的形成仍然是非常未知的。由于MSGLs與快速流動的冰流相聯系的重要性，對它們如何形成的認識的提高將導致影響冰的速度和流量的基本過程的重大進展。這需要在南極周圍發現的MSGLs上進行進一步的研究，而不僅僅是在坑里，以促進知識的進步。
In both Area A and Area C, Mega Scale Glacial Lineation’s (MSGLs) were identified as the main subglacial landform. As shown in Fig 2.2 and Fig 2.4, they can be seen clearly on the high-resolution hillshade raster as ‘ridge-groove features formed in parallel patterns’ (Jakobson et al., 2012). MSGLs can be defined as “linear forms 10,000 to 100,000 m in length, which are most easily observed from aerial photographs or satellite images” (Clark, 1993). These MSGLs are said to have been formed from drumlins, as they are much larger and more elongated, and they provide evidence for areas in which there was a fast ice streamflow. Several theories as to how MSGLs form have been put forward but not one solution has been widely accepted due to the complexity of ice dynamics. Shaw et al. present the idea that MSGLs have been formed through erosion by turbulent meltwater flow however modern observations show that ice-sheet bedforms were created without meltwater floods. Another theory is the “bed deformation model” by that shows that MSGLs were formed through weak sediments being deformed by shear stress imparted on the sediment by the overlying ice. But this theory cannot explain the pattern phenomena through which drumlins and MSGLs form. The instability theory which is the most widely accepted, even though it cannot explain all formation aspects, was presented by Hindmarsh in 1998. It states that the coupled flow of ice and subglacial sediment may be inherently unstable, such that the ice-till surface could become spontaneously wavy with growth at a preferred wavelength. It implies that layers of materials with varying physical properties are prone to the development of instabilities (instabilities being said to occur in a system when small irregularities spontaneously grow to produce regular patterns, in this case, MSGLs). This theory has not been researched enough to conclude whether this is how MSGLs are formed. These theories, plus others, are heavily contested and so MSGL formation is still very much unknown. Due to the importance of the presence of MSGLs linking to fast-flowing ice streams, improved knowledge of how they are formed would result in major advancement of the basal processes that impact on ice velocity and flow. This entails further research being carried out on MSGLs identified around the Antarctic, not just in the PIT, to facilitate this advancement in knowledge.