雅思暑假考試培訓(xùn)

【雅思暑假考試培訓(xùn)】 　　The fertile land of the Nile delta is being eroded along Egypt’s Mediterranean coast at an astounding rate，in some parts estimated at 100 metres per year.In the past，land scoured away from the coastline by the currents of the Mediterranean Sea used to be replaced by sediment brought down to the delta by the River Nile，but this is no longer happening. 　　B 　　Up to now, people have blamed this loss of delta land on the two large dams aI Aswan in the south of Egypt，which hold back virtually all of the sediment that used to flow down the river. Before the dams were built，the Nile flowed freely carrying huge quantities of sediment north from Africa's interior to be deposited on the Nile delta.This continued for 7,000 years，eventually covering a region of over 22000 square kilometres with layers of fertile silt.Annual flooding brought in new, nutrient-rich soil to the delta region，replacing what had been washed away by the sea.