Natural Disasters theme in two volumes is a component of Encyclopedia of Earth and Atmospheric Sciences in the global Encyclopedia of Life Support Systems (EOLSS), which is an integrated compendium of twenty one Encyclopedias. Natural hazards arise unexpectedly, without any discernible regularity, and leave an indelible trace in nature, sometimes for many decades to come. At present they are appreciably complicated by anthropogenic influence, lending them an adverse and often catastrophic character. The susceptibility of a society to the impact of natural disasters is conditioned by the natural environment, and the vulnerability of the society to such phenomena is historically associated with the type of the nature management. Natural disasters can be of geological and hydrometeorological origin; the specific group of such phenomena is presented by natural disasters in mountains. This volume deals with the natural disaster and covers several topics, with a myriad of issues of great relevance to our world such as: Geological Catastrophes; Climate-Related Hazards; Mountain Disasters and Snow Avalanches, which are then expanded into multiple subtopics, each as a chapter. These two volumes are aimed at the following five major target audiences: University and College Students Educators, Professional Practitioners, Research Personnel and Policy Analysts, Managers, and Decision Makers, NGOs and GOs.