Abstract
One of the facts that can be seen in the archaeological contexts of the late Bronze Age in the abandonment or excessive reduction of the enclosures. At the end of the Bronze Age, many sites and settlements in the Iranian Plateau and outside the Iranian Plateau collapsed suddenly and unexpectedly, or the growing process of these societies has stopped. Researchers have considered several factor such as floods, earthquakes, immigration of newly arrived ethnic groups, etc. for this event, to these factors we can also add the effect of factors such as over urbanization, which has not been addressed much. As a result of over urbanization, challenges such as; Regional thermal changes, destruction of habitat and biodiversity and ecosystem as accelerating factors in the crises of this period could further worsen the situation. The result of this research show that after the increase in population in urban centers due to the lack of administrative planning to control the conditions caused by dense urbanization and as a result the disruption on environmental order and natural balance, the society has tried to restore the natural conditions as a stable system this attempt to return to the balance has been manifested in various ways, such as the decision to leave large settlements and move to peripheral and peripheral areas with sufficient food and water resources. The evidence of this event can be seen in areas such as Merv, Northern and Southern Balkh, and Doab areas in eastern Sind; in some cases, the crisis in the societies has increased and it has appeared in the form of newer problems such as famine and epidemics, inter regional conflicts and such things, which have led to the collapse of societies.
Keywords: Bronze Age crisis, Late Bronze, Over Urbanization, Eastern Iran, The Decline of Settlements and Civilization. 

Introduction
Over urbanization or excessive urbanization is generally used in cases where the urban population has grown unplanned and beyond the capacity of the environment and city administration, which causes the transformation and sometimes degeneration of urban communities (see Sovani, 1964). Therefore, the increase in the number of the population and the lack of environmental resources in the administration and organization of the urban population could act as a factor to disrupt the path of the Bronze Age societies. The decline of settlements and civilizations at the end of the Bronze Age is very important, and the first major collapses of the prehistoric era took place at this time, which occurred widely and in large areas of the old land. The Bronze Age in the archaeological literature refers to a period when societies gradually more from rural to more complex or urban and create trans-regional connections. Obviously, what is expected is the continuation of the development and progress of societies towards the emergence of larger and more complex civilization and states, which reached their peak of prosperity during the middle Bronze Age (see Tosi, 1976: 168). But what happened in the late Bronze Age is the abandonment of sites and depopulation of a large number of them, which can be seen as a chronological break in many Ancient sites? The evidence indicates an event during which large settlements such as Shahr-I Sokhta (Tosi, 1968). Mohenjodaro (Wheeler, 1968), Harappa (Wheeler, 1968), Altin Tepe (Masson, 1981), collapsed, although some small settlements such as Tekem Tepe (Kohl, 1984) continued to exist without any interruption. The concentration of population in urban areas and the impossibility of providing in frastructure needs in urban life due to the occurrence of over urbanization had led to disorder in social structures and population decline in Mohenjodaro and Harappa settlements. If the elites of the society do not manage or solve the problems caused by excessive urbanization, difficult conditions will arise and the society will probably solve the problem or become a problem in the form of a self-organizing system. The evidence shows that in some settlements such as Mohenjodaro, Harappa and Altin Tepe, people decided to leave the large settlements and settled in peripheral areas, and this caused the settlements to become uninhabited in the late Bronze Age. 

Identified Traces
Urbanization, which was actually a cultural and social revolution, appeared sometime between the end of the fourth millennium and the beginning of the third millennium bc in western Asia, Egypt and Mesopotamia (Childe, 2019:1). But at the end of the Bronze Age in a wide area of the east, especially the southeast region of Iran and even beyond the current borders of Iran, such as; Central Asia and the Indus valley, many large settlements such as Shahr-I Sokhta (Tosi, 1968), Tepe Hesar (Schmidt, 1937; Dyson, 1989), Namazga (Kohl, 1981) area have declined and shrunk excessively. There are several theories about the crisis of the late Bronze Age, such as the invasion of the Aryan tribes (Girshman, 1954), disease (Robbins Schug et al., 2013), famine and earthquakes (Nur, 2009), etc., but since this discussion is about societies with an advanced level of technology and in constant relations with are their peripheral areas. The factor of excessive urbanization can be added to the above. Rapid urban growth will have consequences for the urban society. Such as the lack and absence of drinking water, urban heat island effects, unpredictable rainfalls, and increasing demand due to population growth cause environ mental destruction and air pollution. For example, in the Indus valley in period IIIC, due to extra-regional trade and large inward migrations, the previous organized settlement pattern was disrupted. The houses in the main areas of the city were thrown into the streets and then at the end of the Harappan phase, the population density decreased and some of them were concentrated in the main areas of the city and the other part moved to the east. In Turkmenistan, even though the archaeological data indicates a decrease in the Kopedagh area, no settlements are abandoned in Atak and other areas, especially Merv and Balkh.

Conclusion
In general, based on archaeological findings, the cities were formed from the old Bronze Age and reached their peak of prosperity during the middle Bronze Age. But at the end of the third millennium and the beginning of the second millennium B.C. the evidence indicates that the sites were excessively shrunk and empty of inhabitants, or the collapse of large settlements. This could have been caused by over urbanization on the basis that whenever the society’s population grows beyond the environmental resources and facilities necessary to organize people, it can create crises for urban societies. Crises such as; the increase in urban rainfall and temperature, the increase in urban waste, the lack of drinking water sources and the destruction of the environment for human well-being in large societies with high population. With the increase of urban population and the lack of resources to organize people it leads to an increase in crime, marginalization and disorder in urban organization, and when the political rulers cannot solve or manage the created problems, the people of the society left the cities and went to the marginal and peripheral areas with stable food and water resources, such as Merv, Northern and Southern Balkh, to continue their lives.