Geoscience Reference
In-Depth Information
Figure 5.12 Location of tropical seasonal forests within the African region.
(Map by
Bernd Kuennecke.)
Origins of the African Seasonal Forests
The origin of the African seasonal forests is similar to the African rainforest dis-
cussed in Chapters 2 and 3. Precambrian basement rock underlies a large part of
the area. Significant tectonic events and severe climatic episodes have influenced
the current distribution of these forests. When rainforests reached their fullest
extent between 35-10 mya, the seasonal forest was much smaller. During this time,
the African continent became permanently connected to Asia (about 20 mya). This
larger continental landmass created drier interior areas and a cooler, drier, and
more seasonal climate in which the seasonal forests expanded and the rainforests
became more restricted. Another cycle of global cooling with increased seasonality
occurred at the beginning of the Pleistocene Epoch about 2.5 mya with the onset
of alternating glacial and interglacial periods. This cycle of seasonal climate re-
stricted the rainforest and expanded seasonal forests again. Glacial cycles contin-
ued throughout the Pleistocene with the last major glacial expansion ending about
18,000 years ago.
