Violent storms flood the rivers by March. Copper accounts for more than 80 percent of Zambia's export earnings. Valuable amounts of cobalt are obtained as by-products of copper mining. Zambia has a lead and zinc mine at Kabwe, and large coal deposits near Kariba Lake. The production of copper products is the country's most important manufacturing activity.
Corn is the most important farm product.
Other leading crops include cassava, coffee, millet, sorghum, sugar cane, and tobacco. Zambia has no outlet to the sea. Railroads connect the country with seaports in Angola, Mozambique, and Tanzania. The railroad to Tanzania was built in the early 1970's with millions of dollars of aid from China. In 1851, the Scottish missionary David Livingstone crossed the Zambezi from the south.