Definition of "sérac"

Perhaps the finest part of it [the Lysjoch] is the grand sérac scenery of the Zwillinge Glacier. In August, 1876, a party of four, having missed the right track in crossing this pass when the snow was in very bad condition, were carried down in an avalanche of loose snow probably started by their own weight.

1838, A Hand-book for Travellers in Switzerland and the Alps of Savoy and Piedmont: Including the Protestant Valleys of the Waldenses (Murray’s Handbooks for Travellers), London: John Murray; Leipzig: Black and Armstrong; Paris: Galignani, page 368, column 2

As you mount the Aletschhorn from the sleeping place, towards the lowest col from which you first overlook the Lotsch Glacier there descends, from a higher plateau, and on your right hand, a large mass of sérac.

1863 March, W. Wigram, “[Notes and Queries.] Intersection of the Lines of Bedding of the Névé by Blue Veins of Pure Ice”, in H. B. George, editor, The Alpine Journal: A Record of Mountain Adventure and Scientific Observation. By Members of the Alpine Club, volume I, number I, London: Longman, Green, Longman, Roberts, & Green, published 1864, page 46

Here and elsewhere the sérac, which is something between curd and cheese, may be advantageously taken instead of butter, which is almost always bad.

1891, The Alpine Journal: A Record of Mountain Adventure and Scientific Observation. By Members of the Alpine Club, volume XV, London: Longman, Green, Longman, Roberts, & Green, page 214