Structural Studies of Glaciers in the Khumbu Region

Abstract

Glaciers in the Nepal Himalaya are different from that in the other regions of the world, because it is composed of immense quantities of rock debris, sands and clays, and its shape and its mode of glacier flow are controlled by unique geological structures which have a great influence on the topography and climate of the Nepal Himalaya. A glacier ice body is thought to be a compound ice body with different structural units and with certain physical properties of glacier ice and of insoluble materials. Each structural unit has characteristics of textures and structures. There are relationships between textures and structures found in the glacier ice body. In the lower ice body, where the strong shear movements are working, ice crystals are granulated to be fine grains and insoluble materials of clays, sands and rocks (which are brought from the bed rock) form the foliation structure. In the middle ice body, the bubble foliation structures are developed and ice crystals have two elongated directions with multiple maxima of the fabric pattern. The strongly elongated direction coincides with that of the glacier flow. In the upper ice body, the ice crystals are polygonal and the bubbles are spherical. The ice body shows no preferred orientation of crystal c-axes without the bubble foliation. Though those textural as well as structural elements are formed under conditions of glacier flow, the glacier flow itself is deeply influenced by the textural and structural elements. Glaciers in the Khumbu region are classified according to structural characteristics of the glacier ice body and there is found a sequence of glacier types which is related to the glacier flow, to topography such as ice falls and to climate such as accumulation and ablation conditions.