1. Department of Geography, Seridó Higher Education Center, Federal University of Rio Grande do Norte, Natal 59078-970, Brazil
2. Centre for Humanities, Literature and Arts, Federal University of Rio Grande do Norte, Natal 59078-970, Brazil
3. Federal Institute of Education, Science and Tecnology of Rio Grande do Norte, Natal 59015-300, Brazil
4. Institute of Earth Sciences, University of Minho, 4710-057 Braga, Portugal