There is more to geology than just rocks, as a visit to the Geology Museum will show. You can discover how Earth was formed, and where we came from too.
QUESTIONS about our origins and how the world was formed have teased the minds of men since time immemorial.
Sedimentary rocks make up three quarters of the erath's surface Sedimentary rocks make up three quarters of the erath's surface Some answers can be gleaned from a leisurely visit to the fascinating Geology Museum at Museum Africa, in the heart of Newtown, Joburg’s inner city arts and cultural precinct.
Katherine James, the curator of geology at the museum, is a fount of knowledge, but points out that all the exhibitions in the Geology Museum are self-explanatory, meaning visitors don’t need a guide for an informative walkabout.
At the entrance, you are greeted by what looks like the surface of the moon, with a picture of Earth in the background. It’s a great photo opportunity, where you can do your best Neil Armstrong impersonation.
Back down on Earth, you can join rock detective Showrock Holmes, a raccoon that takes visitors on a tour of the museum, explaining the techniques used to study the causes of earthquakes, landslides and volcanic eruptions, the formation and composition of Earth and the origins and evolution of life.
Exhibitions are divided into categories, with some focusing on managing natural resources, evaluating how natural processes affect life and how humans interact with the planet.
A significant aspect of geology is the study of how Earth’s materials, structures, processes and organisms have changed over time. Geology has a major influence on most other features, such as land form, soil, topography and vegetation.
South Africa has complex geological history, dating back millions of years, and some of the oldest rocks on Earth have been found here. It is a country rich in mineral deposits, including Witwatersrand quartzite, bushveld igneous and coal deposits found in formations of the Karoo sediments.
Fossil wood turned into rock through permineralisationFossil wood turned into rock through permineralisation“South Africa is, geologically speaking, a very diverse and in many ways unique place, without equal on the globe,” reads an exhibition text, adapted from The Story of Earth and Life: a Southern African Perspective on a 4,6 billion-year Journey, by Terence MacCarthy and Bruce Rubidge.
“There are several factors that contribute to this uniqueness. South Africa has a very long geological history, its oldest rocks dating back some 3 600 million years … the preservation of these ancient rocks is quite remarkable and many look little different today from the equivalent formed in very recent times.”
The geological profile of Earth was formed through millions of years of tectonic shifts, the formation of crevasses, an outbreak of volcanoes and the deposition of gravel and water erosion, according to the one of the exhibits.
There are exhibitions exploring the tectonic plates, rock types and a rock cycle chart that shows each type of rock, and how they are connected. Arrows point from one rock form to a new form that it can become over time, describing the process Earth uses to recycle rocks.
Igneous, metamorphic and sedimentary are the three basic types of rock, all of which can be changed into one of the other types through geological processes. Their names refer to the way the rocks are formed: igneous rocks are formed from fiery molten magma; metamorphic rocks form under intense heat and pressure; and sedimentary rocks are formed through weathering.
The oldest rock materials found so far are tiny crystals, embedded in younger sediments, from Australia. They are about 4,4 billion years old. The oldest continental crust, which includes sedimentary rocks, is from Greenland and was formed between 3,9 and 3,8 billion years ago.
A molten rock turned into an igneous rock after coolingA molten rock turned into an igneous rock after coolingHowever, the best place to study evidence of the ancient oceanic and continental crust is the Barberton Mountain in Mpumalanga, to the east of Gauteng.
Johannesburg has its own fascinating history. Since the main gold reef was discovered in Johannesburg in 1886, more than 50 000 tons of gold have been mined from under us –about 31 percent of all the gold ever mined.
There is no agreement among scientists as to how so much gold became concentrated in such a small area, or where it came from. In the last stages of the Witwatersrand sedimentation, the crust fractured and broke apart, forming rifts. The outpouring of lava from these rifts covered the sedimentary basin, ending the depositing of the gold-rich Witwatersrand sediment.
From rock, to living creatures: the museum also covers early complex life forms. Its exhibitions show that the diversification of life started 543 million years ago, and contrast this with stories about the discovery of gold.
It says that about 1,3 billion years ago, fungi may have formed and about 575 million years ago, the first example of complex life happened.
But how did it all begin? Scientists believe that Earth was once in the form of a fiery gas and that all the planets and satellites that exist were once a part of that mass of gas. After a geological process of heating, cooling, shrinking and whirling, the parts of that mass of gas began to separate and the globe that we now stand on was formed.
Soon, water was reduced from a gas to a liquid and began filling the surface; and so the ocean began to be formed. The water grew in depth until nearly all the steam was condensed, except the gases that cannot easily be condensed. They formed the air that we breathe.
A torshion, used to scout for goldA torsion, used to scout for goldBut this is just a theory, and many scientists disagree with it, saying much of the evidence presented cannot be substantiated.
According to some of the exhibits, Earth was formed about 4,6 billion years ago from the accretion of smaller planetesimals orbiting in the same orbit. Frictional heat caused by the accretionary process, as well as nuclear heat caused the early Earth to become entirely molten. It was constantly bombarded with asteroid-type material attracted to it by its gravitational force.
The Nebular theory, the most widely accepted model explaining the formation of the solar system, also estimated to have begun some 4,6 billion years ago, is also explained in detail.
Moving on: Africa is Earth’s second largest continent, covering about 30 065 000 square kilometres – 20,2 percent of Earth’s land surface.
Visitors can also read about Alex du Toit, a South African geologist who was one of the earliest to accept the theory of continental drift as proposed by Alfred Wegener. Wegener’s ideas were condemned because his suggestion that continents could float like a boat seemed impossible.
Du Toit suggested that there were two ancient continents – the southern continent of Gondwanaland, which includes Antarctica, Australia, the Indian peninsula, Africa, Madagascar and South America; and a northern continent called Laurasia, comprising North America, Greenland, Europe and Asia.
New evidence that came to light in the 1960s in the field of palaeomagnetism supported his idea of continents moving.
Plants and dinosaurs
Approximately 350 million years ago, plants first developed seeds and the earliest dinosaurs first started to appear some 255 million years ago. An asteroid wiped out dinosaurs some 65 million years ago, it is believed, and an animal resembling the modern dog lived about 35 million years ago. The divergence of the orang-utan and human lineage happened some 16 million years ago, and at about 1,2 million years ago Homo erectus began the global trek to Asia and Europe.
The treasure room features an array of minerals from around the worldThe treasure room features an array of minerals from around the worldThe oldest known human existed about 600 000 years ago.
The most spellbinding subject the geology museum touches on is the Big Bang theory and the age of the universe.
Scientists believe that the universe was infinite, with no beginning or end; however, this was before the inception of the Big Bang theory, estimated to have taken place about 15 billion years ago. The Big Bang theory is attributed to Edwin Hubble, who observed that the universe was continuously expanding in every direction. He discovered that a galaxy’s velocity is proportional to its distance.
Since the Big Bang, the universe has been continuously expanding and, thus, there has been more and more distance between clusters of galaxies, scientists believe.
Back to the rocks
Visitors to the museum can also learn about the oldest rocks in the world, different minerals found in rocks, and pumice, a kind of lava that has air pockets formed by gas bubbles, enabling it to float, to mention a few of other widely covered subjects. And there is an Earth quiz.
The treasure room has a collection of fabulous minerals and gorgeous gem stones from all over the world and replicas of famous diamonds, says James.
“All the displays that are kept open are meant for people to touch and feel the texture of the exhibits,” she says.
The Geological Museum at Museum Africa has a fascinating collection of geological artefacts. Watch video.
The Geology Museum took about 18 months to set it up and was opened in April 2010. Museum Africa is at 121 Bree Street, Newtown. To book a tour, telephone 011 833 5624 or fax 011 833 5636; alternatively send an email to firstname.lastname@example.org.
Entrance is free and the museum is open from Tuesdays to Sundays, from 9am to 5pm. It is closed on Mondays, Good Friday, Christmas Day and Day of Goodwill.
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