PTE Core Reading Test 6

The Sahara Desert, the largest hot desert in the world, has not always been the arid expanse it is today. Geological and archaeological evidence reveals that, between roughly 11,000 and 5,000 years ago, much of the region was remarkably green. During this period, often called the African Humid Period, the Sahara was dotted with lakes, rivers, and grasslands that supported a rich variety of plant and animal life. Ancient rock paintings discovered across the region depict creatures such as giraffes, hippopotamuses, and crocodiles, animals that could never survive in the desert as it exists now.

The cause of this dramatic transformation lies in subtle changes to the Earth's orbit and the tilt of its axis. These shifts altered the amount of sunlight reaching the Northern Hemisphere, which in turn strengthened the seasonal monsoon rains that fed the region. As the orbital conditions gradually changed again, the monsoons weakened, rainfall declined, and the landscape slowly dried out. Vegetation disappeared, lakes evaporated, and human populations were forced to migrate towards the Nile Valley and other areas where water remained available.

Scientists study this episode not merely out of historical curiosity but because it offers insight into how sensitive climate systems can be to relatively small changes. Understanding why the Sahara shifted from green to gold may help researchers anticipate how modern climate change could reshape other regions of the world in the centuries to come.

According to the passage, what was the primary cause of the Sahara's transformation from a green landscape to a desert?

1. A.Changes in the Earth's orbit and axial tilt that weakened the monsoon rains.
2. B.The migration of human populations away from the region.
3. C.The disappearance of large animals such as giraffes and hippopotamuses.
4. D.A sudden increase in volcanic activity across North Africa.

The correct answer is shown in your review when you finish the test.