Londolozi has recently gone through a great change. The new rains arrived, creating the perfect setting for brand new bushwillow buds to bloom, watering holes have filled up, and migratory birds followed their path back home. There are, however, certain elements that we cannot witness the changes to, elements that take millions of years to change. Today’s blog is an ode to one of those elements – our landscape geomorphology.
Geomorphology | ˌdʒiːə(ʊ)mɔːˈfɒlədʒi
The study of the physical features of the surface of the earth and their relation to its geological structures.
We owe a lot to our geomorphology and how it has resulted in a diverse, dynamic, and desirable landscape, attracting thousands of grasses, trees, birds, and animals.
A brief of Londolozi’s landscape
Londolozi is an incredible piece of land: unending undulating crests tower over the path of riverbeds weaving their way into the Sand River, followed by gaping grasslands that extend for as far as the eye can see. All the different elements in our landscape are here because of the basic geology of the land. In other words, everything we see here is the result of underlying rocks. Over millions of years, these rocks have gone through various climatic changes and volcanic activity to produce the landscape that we see today.
Londolozi falls within the Lowveld of South Africa: a region lying at a low altitude of about 350 metres above sea level. This area is underlain with granite rock. This rock formed 3 500 million years ago when magma rose underneath the ground and cooled. The granite was eventually exposed to the atmosphere as the earth above it eroded away. As granite is much harder than the earth’s soil, it doesn’t weather as quickly and so it forms the crests in our landscape.
Granite rock and the catena
To understand the impact of granite on the landscape, we must look at the basic mineral composition of granitic rock, and the types of soils these minerals produce. Granite is composed of quartz, feldspar, and mica. After weathering, the quartz in granite forms coarse sandy soils and the feldspar forms fine-grained clay soils. The arrangement of these soils along a slope and the resultant vegetation is known as a catena. The Lowveld’s topography gently undulates with the catena repeating itself across the landscape, which is seen in Londolozi with our congregation of crests.
How does the catena system influence our landscape?
Well, starting off at the top of the crests and working our way down:
Large coarse-grained sand particles are found at the top of the crests. Being heavy, they aren’t moved easily by wind or water down to the lower part of the hills. The large grain sizes allows for aeration and water infiltration. Marula trees, bushwillows and other large-leafed trees have a large root system and favour these aerated and well-drained soils. On the downside, sandy soils are not very nutrient-rich. They produce grasses that are less favourable for animals, such as common finger grass and cat’s tail. This doesn’t stop animals from grazing in these areas, though. Wildebeest and impala are attracted to the stems of golden finger grass sprouting from the sandy soils, while large herds of elephants pass through the towering trees, trunks stretching high into the canopy to collect the crisp marula fruit.
The finer clay particles are much lighter and are easily pushed to the bottom of the crests by wind and rain. Because of their smaller particle size, clay soils are not as aerated or well-drained as sand. However, they have a lot more nutrients and are therefore more fertile. As a result, this soil produces highly nutritious grasses, for example, guinea grass and spear grass, which are favoured by most grazers. These areas are also ideal for the growth of woodland trees (acacias, jackalberrys, leadwoods and sausage trees), attracting a variety of browsing animals. A memory etched in my mind has been watching giraffes gather at the foot of a crest, and gently strip the acacia leaves and thorns from the budding branches. At their feet, the nyala picked at the blazing red flowers of the sausage tree that had drifted to the dust after a windy day.
The knock-on effects of the catena
As somebody who absolutely loves seeing the connections of different elements in the landscape, it blows my mind how one element can produce a succession of knock-on effects. The giraffe and nyala I saw that day would not have been there if not for the acacia and sausage tree. These trees wouldn’t have been able to grow without the conditions of the clay soil. And this clay soil wouldn’t have been in the area if it weren’t for the underlying granite rock weathering away over millions of years. Everything we see here today on Londolozi we owe to our geomorphology: the granite rock and the catena system it has produced.