This mountainous area forms the barrier between Cameroon's forested south and savanna north. At almost 64,000 kmÂ² in land area, the Adamawa is the third largest of Cameroon's ten regions. The land is rugged and sparsely populated, however, as most is devoted to the rearing of cattle. The Muslim Fulbe (Fulani) form the major ethnic group, though Tikar, Gbaya, and other peoples are present in lesser numbers. In 2008, the President of the Republic of Cameroon, President Paul Biya signed decrees abolishing "Provinces" and replacing them with "Regions". Hence, all of the country's ten provinces are now known as Regions. The Adamawa is one of Cameroon's more geologically diverse areas. The Gotel and Mambila Mountains at the border with Nigeria are largely composed of granite, which gives way to crystalline and metamorphic rock such as mica, schists, and gneiss. These are often covered in volcanic basalt, a combination that dominates until the Faro River. East of this, granites once again prevail, though sedimentary rock forms the valley of the MbÃ©rÃ© River, and a zone of metamorphic rock surrounds this. The Lom River also rises in a region of metamorphic rock. Volcanic rock occurs in the northwest just east of the Gotel Mountains and northeast of NgaoundÃ©rÃ©, the provincial capital, along the border with the North Province.