The Sahara is the world's second largest desert after Antarctica. At over 9,000,000 square kilometres, it covers most parts of northern Africa. Its name derives from an Arabic word meaning "desert".
The Sahara covers huge parts of Algeria, Burkina Faso, Chad, Egypt, Libya, Mali, Mauritania, Morocco, Niger, Western Sahara, Senegal, Sudan and Tunisia.
The climate of the Sahara has undergone enormous variation between wet and dry over the last few hundred thousand years. During the last ice age, the Sahara was bigger than it is today. The end of the ice age brought better times to the Sahara. Once the ice sheets were gone, the northern part of the Sahara dried out. However, not long after the end of the ice sheets, the monsoon which currently brings rain to the Sahara came further north and counteracted the drying trend in the southern Sahara. By around 2500 BC, the monsoon retreated south to approximately where it is today. The Sahara is currently as dry as it was about 13,000 years ago.