The existence of Ancient Egypt as ancient culture depended on the annual flooding of the Nile river. Rich in trace elements and organic substances, water is periodically poured a vast valley, maintaining the fertility of local soils. This led to the development of agriculture in the region. For this reason, almost all the major Egyptian cities were built in the river valley.
Flooding of the Nile, in turn, depends on monsoon rains in the Ethiopian highlands. The rainy season begins in June and continues through December, with peak precipitation occurs in the summer season. The ancient Egyptians started planting in October, when the river water receded, revealing the muddy understand. However, in some years almost no Nile flooded the valley, which led to crop failures and hence abrupt changes in the economy and politics.
Scientists have found that volcanic eruptions, during which the Earth's atmosphere is subjected to large amounts of airborne particles can be the cause of the fall of the water level in the Nile. Because the particles contribute to the fact that more sunlight is reflected from the gas envelope of a planet back to space, it affects the distribution of heat and precipitation around the globe.
According to historical records, one of the bad periods of flooding of the Nile occurred during the reign of the Ptolemaic dynasty. Around the year 44 BC, when Egypt rules the Cleopatra, in different parts of the globe there is a powerful volcanic eruption. Ash and hot gases breached the monsoon cycle, has reduced the water level in the Nile and caused a serious famine.