Siltation is a process by which water becomes dirty as a result of fine mineral particles in the water. Explanation: When sediment, or silt, is suspended in water, this is an example of siltation.
The common geographic factor for Egypt and the fertile crescent were the big rivers, they made big alluvial deposits on their shores each year and allowed the people to have sufficient amount of food production. That opened the gates for civilizations to flourish in this places.
