Archaeology is the study of human activity in the past, primarily through the recovery and analysis of the material culture and environmental data that has been left behind by past human populations, which includes artifactss, architecture, biofacts and cultural landscapes . Because archaeology employs a wide range of different procedures, it can be considered to be both a social science and a humanity and in the U.S, it is thought of as a branch of anthropology although in Europe it is viewed as a separate discipline. A historian<span> is a person who studies and writes about the past and is regarded as an authority on it.</span><span> Historians are concerned with the continuous, methodical narrative and research of past events as relating to the human race; as well as the study of all history in time. If the individual is concerned with events preceding written history, the individual is a historian of prehistory</span><span>. Although "historian" can be used to describe amateur and professional historians alike, it is reserved more recently for those who have acquired graduate degrees</span><span> in the discipline. Some historians, though, are recognized by publications or training and experience.</span><span> "Historian" became a professional occupation in the late nineteenth century as research universities were emerging in Germany and elsewhere. </span> Geographers study the earth and its land, features, and inhabitants. They also examine phenomena such as political or cultural structures as they relate to geography. They study the physical and human geographic characteristics of a region, ranging in scale from local to global.
Mudflows of volcanic eruptions are the most dangerous, and are called lahars. A lahar is a type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water.
