Geology weekend 21 May – 23 May 2021

Report by Lebo Augistin, edited by Jane le Roux. Photographs by Jane le Roux

A TRIBUTE

We give tribute to Maria Cazzavillan and Bob Scholes, two great people that we as a group were privileged to meet during our Bushveld Mosaic course. May they both be remembered for their remarkable contributions to Bushveld Mosaic and the preservation and enjoyment of our natural environment.  We are forever grateful. May they rest in peace.

Thank you, Peter, for your tribute around our “campfire” lecture area. It was a special moment, and I am sure they were listening. Especially Maria, who held a special place in the lives of many students past and present.

THE WEEKEND

Despite the cold, it was an amazing weekend. We really appreciated the change of venue to the warmer learning centre, especially when we were writing the Veld Management test.

SATURDAY, 22nd MAY 2021

It was a pleasure to meet our lecturer, Patrick Richards, who shared his knowledge and great passion about the wonders of nature beneath our feet and who, during the course of the weekend helped us to understand (mostly!), a multitude of new terms such as igneous, asthenosphere, mafic, felsic, hyperbyssal, plagioclase, feldspar, and metamorphic, just to name a few.

We learned that all known life on earth is found on the narrow outer surface of the earth’s crust. We also learned that the earth consists of three main layers, namely the crust (outer layer), the mantle (comprised of partly a layer with plasticity and a rigid upper layer), and the core (consisting of two parts – a solid inner core and a molten outer core).

Elements form minerals, and minerals in turn form rocks. We learned that the earth’s crust is dominated by 8 elements and has three different rock types which are igneous, sedimentary and metamorphic rocks.

Igneous rocks are formed by the crystallization of the liquid material either beneath, or on the earth’s surface. We learned that this rock forming-material is also referred to as magma before it erupts on the earth’s surface, or lava when it spills out onto the earth’s surface and is thought to originate from batholiths in either sills or dykes. Igneous rocks are further divided into intrusive and extrusive igneous rocks. Intrusive igneous rocks crystallize below earth’s surface and the slow cooling allows large crystals to form. Extrusive igneous rocks erupt onto the surface, where they cool quickly and are therefore fine grained.

Sedimentary rocks are formed by the accumulation of sediment in a basin which is later lithified into a rock. These sediments are subjected to a process of weathering by physical, biological and chemical forces. Sedimentary rocks are the most abundant rock type in South Africa and occupy large sections of the earth’s surface. Sedimentary rocks are predominantly made up of layered material often containing structures such as ripple marks.

After each section of the lectures, we went through various rock samples on the trays to illustrate what we had just learnt. We then went out to a quarry near our campsite and received new insights into what caused the various structures and patterns that we have passed so often without understanding its components.

The day ended well and I now have a different view and appreciation for previously unnoticed things.

SUNDAY, 23 MAY 2021

Sunday morning lectures started with learning about metamorphic rocks. Metamorphic rocks were originally igneous rocks, sedimentary rocks or other metamorphic rocks, and have been altered, by high temperatures and/or pressure to form different rock types, for example, sandstone originally a sedimentary rock becomes quartzite.

Patrick then moved to structural geology with concepts such as transform, normal and reverse/thrust faults and the effects they have on the shape of the earth’s surface. We also dealt with the major tectonic plates and the continual movement of the crustal material, looking at features such as mid-oceanic trenches and ridges found on the bottom of the oceans. We were then introduced to how mountains are built from the collision of plates and the distribution of volcanos and earthquakes on the earth’s surface. 

To end our morning of learning we went to Pitjane Hill where Patrick encouraged and assisted all of us to observe aspects such as cleavage in the beautiful pink granite found in that area.

As we called it for the weekend, I personally have started seeing the earth and its organisms differently and it is amazing that some of the simplest things can have such a wealthy history.

Who would ever think that the earth has been in existence for many billions of years, and that the earth has such a variety of rocks which I believe plays a very important role in how nutritious the soil is, which in turn determines the trees and grasses growing in an area, which then  determines the animals, insects and birds in an area.

ED’S NOTE: Many thanks to students Lebo for this insightful write up and Jane for the pictures. No mention of the temp so Bora in May was certainly warmer than Bora in June.

Bushveld Mosaic a course for the curious, fun loving, serious, passionate or career-minded nature enthusiast!

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