Part I – Tectonics, Glaciers and Time
Introduction
The terrestrial forces of tectonic plate movement, ice ages and volcanic activity, together have changed the earth like no other forces except collision with extraterrestrial bodies. Southeast Africa has strategically benefited from these earth changing forces. This can be seen in the generation of a widely varied collection of mega and micro fauna and flora like no other place.
The introduction picture shows a 7 zebras and 5 wildebeest in the Ngorongoro Crater. We went there using safari vehicles in 8/2025. The only road was made of irregular stones, ruts and dirt. Driving was difficult. Visibility was obscured for hours by dust as we drove across the crater. It is the caldera of the worlds largest above water volcano that was active 2.5 million years ago. It was famous for its wildlife. The image shows the greatest concentration of animals which we encountered along the way. To say that it was disappointing is an understatement. Fig. 10 comes from a posting on the internet.
Changing forces
Today we can see that the forces are changing. Tectonic plate is the slowest acting force acting in the level of hundreds of millions of years. And yet its rate and direction of movement can change dramatically in regions. This may be caused because glaciers and ice shelves are reduced. Glacialization operates at more rapid rate than plate movement with an effective speed measured in thousands of years. As the ice melts the weight of the water is more evenly distributed to the oceans thus altering the plate movement location and location of volcanic activity. Notably, the rate of vulcanism is unchanged. Volcanic ash, carbon dioxide and sulphur and gases are insignificant when compared to human activity. Anthropogenic CO2 emission for 2010 is estimated to be about 80 to 270 times larger than the respective maximum and minimum annual global volcanic CO2 emission. The results of action and reaction of human intervention parallel a cause and effect interference with historic geologic cyclical behavior. This may be the root cause of two possible effects of biological changes which are currently occurring. Survival of existing species is in decline. Generation of new species has slowed. This series of postings uses a contrast of two cat species, lions and cheetahs in Southeast Africa. Study of these species is intended to form a foundation for understanding how the change in the forces drive the current ecological conditions.
These four blogs are the result of thoughts and interpretations based on our latest safari to Africa that included Kenya and Tanzania. This was not a high-end trip. Instead it was a road trip to some of the lesser visited sights and it was during a period that was unexpectedly dry. I was particularly interested in the survivability of two well recognized cat species. The lions and cheetahs are two very different genus of predatory cat species at the apex of the food chain.
VOCABULARY
The vocabulary in these post also include several technical terms that apply to our discussion. For definitions, follow their links. Genetic drift, founder effect, gradualism, saltation, adaptive introgression and hybridization.
Let’s look at the driving forces and their results. The following charts show the approximate location of the Great Rift Valley region in Southeast Africa. This is a massive geologic event which is actively happening as we watch. The continent is splitting the eastern quarter of the continent off the main body. This gigantic split has created a huge valley that will someday be filled with ocean. It is accompanied by volcanoes, earthquakes, lava flows and uplifting plateaus.
GLACIAL REBOUND
From the last two glacial periods, 21,000 and 13,000 years ago, the continents are still recovering. The ice pack at the poles still hold the last remnants of that ice age. One result of this diminishing ice can be seen in the African desertification. The Sahara and Kalahari deserts are the result of the last ice age. When the poles melt and the Rift Valley floods the main portion of the African continent will recover. The deserts will bloom and the chronic drought in Africa will be concluded. The new continent will be created east of the Rift Valley. Migration may reverse. It just takes time. Never-the-less, the adaptable survivors will prevail.
ECOLOGIC BARRIERS
As a result of the climatic changes, geographic barriers emerged. These are called Walls and they divide Africa into three eco regions.
These include the Saharan desert, the sub Sahil West-Africa separated from the Sahara by the line called the wall called the Sahil and East-Africa with Great Rift Valley, Fig.4, separated from wast Africa by the Great Wall of mountains.
The Great Walls of Africa limit the direction of animal migration and isolate the wildlife. This isolation has a double effect on all life forms by promoting speciation but also risking the compromises of genetic drift. In Fig. 5 the Sahil, shown as a green line, is the wall created by the Sahara. The Great Wall of mountains shown as blue line of Fig.5 parallels the Great Rift valley. Note that the regions of Kenya and Tanzania, Fig. 6 outlined in blue, are in high arid, desert risk locales.
MIGRATION
Through the two Great Walls there are narrow gaps called “bottle necks” . These geographic locations limit commingling and migration of species. These are the few areas through which animals can migrate. Except for the Nile river flowing through the Great Rift valley none of these areas follow the seasonal north-south wet weather patterns nor a river flow to another land mass. The access to Eurasia from the generative basis of Africa is through the three bottle necks of the Straights of Gibraltar, the Nile river delta and the Straight of Bab Al Mandeb. During the last 12,000 years the shallow Nile river delta crossing has been the least treacherous.
The illustration Fig. 7 is a conceptualization of the most direct routes for migration. Interestingly the Great Migration for animals from Africa also follows the projected route for hominoid migration. Mov.1.
The illustrated route could be followed in both directions as driven by climate change and the paths of migration of predated species sought after by the apex predators. As the glaciation advanced or retreated these routes would have water which would support grasses, insects, herbivores and carnivores. The Nile is the only north /south river. It flows to the Mediterranean through the Great Rift valley. Following the Valley waterway this leads to the choke points to the Eurasian continents. Following the east west routes of the Congo River, the Niger River or the Zambezi River leads to migration potential but dead ends at the two vast oceans.
We will follow two cat species which are the result of adaptations after the last Glaciation period. Panthera contains the largest number and variety of living members of the cat family. There are five living species: the jaguar, leopard, lion, snow leopard and tiger. It contains the five living species of “big cats” capable of roaring. Cheetahs belong to a completely different biological genus (Acinonyx). They cannot roar, have distinctly different anatomy, including semi-retractable claws for high-speed traction and a unique, lightweight skeleton
Continue to follow this amazing story of Earth changing forces. See the combination of struggle, adaptation and survival of life that sweeps across the planet through hundreds of thousands of years. Learn about the unique capabilities and risks to the Cheetah and the Lions. Because we are part of this great drama, you may use this knowledge to anticipate our future.
All photographs created by John Knapp
References:
Mitogenomic analysis of the genus Panthera
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