First a small bit of history about where you are standing
"Construction of the Shongweni dam was started in 1923 and completed in 1927 with the wall being hailed as an engineering phenomenon. The Hydroplus fuse gate system was added later. The fuse gate ensures the dam’s stability and the discharge capacity. The project was awarded the South African Institution of Engineers Award for Technical Excellence in 1995. The original water works located below the wall has been proclaimed as a national monument."
But that is enough history lets get down to the science and why we are here EARTHCACHE!!!!!
This is another of our Earthcaches we aiming at the younger geocachers and even those that are trying to learn a bit more the easy way.
To start let answer a simple question that most people may assume or take for granted :
What is a Rock
Well according to my internet research "A rock is a solid collection of mineral grains that grow or become cemented together. Some rocks are large while others are small. Small rocks are called pebbles. Every rock is made up of one or more minerals. Geologists (people who study rocks and minerals) classify rocks according to the way they are formed. The three main types are igneous, sedimentary, and metamorphic rocks."
Interesting there are different types of Rocks and they clearly mention the 3 main types. Lets look at these types in a little more detail. (a bit more reasearch later trying to find the simplest explination of these types and I got these)
Igneous Rock
"Igneous rocks form when magma (molten rock) cools and becomes solid. If this happens underground, the magma solidifies slowly, giving large crystals time to form. The magma becomes a hard rock, such as granite. Igneous rocks can also form on the Earth’s surface when lava escapes from a volcano and solidifies quickly. Lava is molten rock that has reached the surface of the Earth. The lava forms rocks with tiny crystals, such as basalt."
Sedimentary Rock
"When rocks are weathered and eroded (worn down), they break up into smaller pieces called sediment. Over time, the sediment may be moved by wind, rain, and flows of ice to rivers, lakes, and oceans. Some sediments form by chemical processes such as the evaporation of seawater, which leaves salt behind. Other sediments form from the skeletons of animals, and from plants and other living things. Eventually, these sediments get buried and are squashed together to form sedimentary rocks. "
Metamorphic Rock
"Metamorphic rocks are rocks that have been changed by heat or pressure, or both. Originally, they were either igneous or sedimentary rocks. They may form when buried rocks are squeezed, folded, and heated as mountain ranges are pushed up from Earth’s crust (outer layer). Other metamorphic rocks form when the rocks surrounding super-hot igneous rocks are baked by the high temperatures."
Ok that is a simple enough to understand but what about the other little bit that we find in the rocks the ones refered to as Minerals well lets see what we can find out about those:
Minerals
"A mineral is a naturally occurring, solid, inorganic substance, which means it doesn’t come from the remains of plants or animals. Minerals are made of chemicals. Most minerals are made up of repeating structures called crystals. Minerals grow or cement together to form rocks. Minerals are everywhere you look. Some metals are even held inside rocks as minerals. The rock or mineral that holds the metal is called an ore. An ore is heated with chemicals until it melts and the pure metal separates out as a liquid. The liquid then cools and hardens. A few metals, such as gold, silver, and copper can be found in pure form as metal elements. Nuggets or flakes of these metals can be taken straight from rock, but this is uncommon. Metals are used to make many familiar things around us, such as copper in electrical wires, aluminum in soda cans, iron in saucepans, and solid gold in jewelry."
Ok this is very interesting information but what has that got to do with why I am standing below a dam wall by a little river. Well that is where the fun part come in:
Tasks
Task 1 : For History sake - What was the original name of the Dam (answer can be found on the plaque by the parking Co-ordinates)
Task 2 : Look at the river in front of you and look at the rocks and see if you can spot any minerals in them and even possibly try and guess which of the 3 types of rock they are made from.
Task 3 : (Optional) Take a photo of some of the interesting things you find in the rocks and include them in your log (try and include the dam wall in the photo as well seems it has a great place in history too)
Task 4 : Look at the cliffs that tower above you on the other side of the river. Now by looking at them can you tell which of the 3 types of rock mentioned above they are made from? Why do you think this (give reasons for you answer)
Task 5 : Time to estimate - How high would you say the cliffs are ?
Task 6 : If you look at the Filtration ponds a little lower down the river (Waypoint supplied) you will see they are madu up of 2 main substances that we come into contact with every day that come from Rocks - what are they?
Please email your answers to us or send them via the geocaching messageing center that can be found on our profile page.
Acknowledgments
https://www.dkfindout.com/us/
http://msinsi.co.za/shongweni/