The axial morphology of the Southeast Indian Ridge (SEIR) between Australia and Antarctica changes dramatically along 120 o E to 127 o E (Fig. 1). At approximately 127 o E the ridge changes character along with a difference in water depth of about 1 km. Eastward it changes from a Mid-Atlantic Ridge (MAR) type cross-section to an East-Pacific Rise (EPR) type cross-section (Fig. 2). The MAR profiles a bathymetric low (5- to 20-km wide, 500- to 1500-m-deep rift valley), while the EPR profiles a bathymetric high (10-km-wide, 500-m-high ridge). The MAR type extends westward to approximately 100 o E and is called the Australian-Antarctic Discordance (AAD). This geomorphology is unique globally. The MAR is considered a slow-spreading center and like the AAD has similar segmentation characteristics of non-transform (small, 10 km) and transform discontinuous partitions of the ridge at 40 to 60 km. In contrast, the SEIR east of the AAD has segmentation characteristics of a fast-spreading center like the EPR. There are no transforms until 138 o E, and westward propagating rifts are the only non-transform discontinuities.
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机译：澳大利亚和南极之间的东南印度山脊（SEIR）的轴向形态沿120℃变化到127 o E（图1）。在大约127 o e柱上，脊改变性格以及水深的差异约为1公里。向东时，从中大西洋山脊（MAR）类型的横截面到东太平洋上升（EPR）类型横截面（图2）。 MAR型材是一个碱度的低（5到20公里，500至1500平方米的裂谷），而EPR曲线概况高（10公里宽，500米的山脊）。 MAR类型向西延伸到大约100℃，被称为澳大利亚南极义务（AAD）。这种地貌在全球之外是独特的。 MAR被认为是一个缓慢扩散的中心，就像AAD一样的非变换（小，<10km）的分割特性，并在40到60公里处改变山脊的不连续隔板。相比之下，AAD东部的SEIR具有像EPR这样的快速扩展中心的分割特征。直到138 o E的转变，向西传播裂缝是唯一的非变换不连续性。
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