Khumbu Himal — Ergebnisse des Forschungsunternehmens Nepal Himalaya Band 1 / 3. Lieferung

Free and covered ablation. The ablation of ice that is either free and open to the air or covered with other materials (with sand, rubble or boulders; on glaciers with moraines) comes to pass by physical processes, that can be described by equations. The amount of the ablation can be calcu­ lated, but depends on so many parameters, that it is not possible to show all connections of the ablation processes in one single diagram. Therefore in chapter 2 and in the appendix many dia­ grams are shown, that represent the dependence of the ablation on the different meteorological factors and-in case of covered ablation-on the heat transmission coefficient ofthe covering mate­ rial. The differences between free and covered ablation become especially clear. From these dia­ grams, too, one can take the amounts of selective ablation that is caused by other processes than by the difference in the covering. By using the equation of energy balance it is possible to inter­ prete these processes. The third chapter shows many illustrations about the glaciers and the small glacial forms of ablation in the environs of the Mt. Everest. The phenomenons shown on these photographs be­ come intelligible by the physical considerations ofthe first and the second chapter. EINLEITUNG Die Abtragung von Schnee und Eis nennt man Ablation; sie erfolgt vor allem durch Schmelzen und Verdunsten.