<P> Trans - Saharan trade requires travel across the Sahara (north and south) to reach sub-Saharan Africa from the North African coast, Europe, to the Levant . While existing from prehistoric times, the peak of trade extended from the 8th century until the early 17th century . </P> <P> The Sahara once had a very different environment . In Libya and Algeria, from at least 7000 BC, there was pastoralism, herding of sheep and goats, large settlements and pottery . Cattle were introduced to the Central Sahara (Ahaggar) from 4000 to 3500 BC . Remarkable rock paintings (dated 3500 to 2500 BC), in places which are currently very dry, portray vegetation and animal presence rather different from modern expectations . </P> <P> As a desert, Sahara is now a hostile expanse that separates the Mediterranean economy from the economy of the Niger basin . As Fernand Braudel points out that crossing such a zone (especially without mechanized transport) is worthwhile only when exceptional circumstances cause the expected gain to outweigh the cost and danger . </P> <P> Trade, beginning around 300 CE, was conducted by caravans of camels . These camels would be fattened for a number of months on the plains of either the Maghreb or the Sahel before being assembled into a caravan . According to Ibn Battuta, the explorer who accompanied one of the caravans, the average size per caravan was 1,000 camels; some caravans were as large as 12,000 . The caravans would be guided by highly paid Berbers who knew the desert and could ensure safe passage from their fellow desert nomads . The survival of a caravan was precarious and would rely on careful coordination . Runners would be sent ahead to oases so that water could be shipped out to the caravan when it was still several days away, as the caravans could not easily carry enough with them to make the full journey . In the middle of the 14th century Ibn Battuta crossed the desert from Sijilmasa via the salt mines at Taghaza to the oasis of Oualata . A guide was sent ahead and water was brought on a journey of four days from Oualata to meet the caravan . </P>

Why was the gold/salt trade significant and what was the role of islam in that trade