EDUCATIONAL LOGGING REQUIREMENTS
In order to substantiate your visit and comply with the educational requirement for Earth Caches you have to submit your answers to the following questions to the cache developers via their profile:
For purposes of logging this cache you must answer the following three questions.
1) Describe the rock formation with regard to size, colour and texture.
2) Is the formation natural or was the rock placed?
3) Do you think the rock is igneous or sedimentary?
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The Tropic of Capricorn
The Tropic of Capricorn (or the Southern Tropic) is the circle of latitude that contains the subsolar point on the December (or southern) solstice. It is thus the southernmost latitude where the Sun can be directly overhead. Its northern equivalent is the Tropic of Cancer.
The Tropic of Capricorn is one of the five major circles of latitude that mark maps of the Earth. As of 3 August 2016 (the date of placement of this cache), its latitude is 23°26′13.7″ (or 23.43713°) south of the equator, but it is moving northward, currently at the rate of 0.47 arcseconds, or 15 metres, per year. The actual circle is now approximately 200m north of the line in the tar road meaning that it was laid in approximately 2003.
Geology of the area
The geological map of the Kruger National Park is dominated by igneous rock with granite, gabbro and basalt covering the largest park of the surface area. To the north there are small areas of conglomerates, shale and sand deposits. There is also a small belt of ryolite on the western border.
There is a rock formation at the published coordinates with a plaque. You must examine the formation to answer the questions above.
Igneous Rocks vs Sedimentary Rocks
Rocks in the earth’s crust can be broadly categorized in to three types. Those major rocks types are igneous rocks, sedimentary rocks, and metamorphic rocks. Geologist made this classification based on the geological process, which formed the given rocks. Igneous rocks are formed when melted rocks cool and solidify. Sedimentary rocks are formed when sediments get solidified. Metamorphic rocks are rocks that have changed from igneous rocks or metamorphic rocks. Like water cycle, there exist rock cycle (geological cycle) in geology. Rock cycle means the process by which rocks are formed, degraded, and reformed by the internal geological processes like plutonism, volcanism, uplift etc and/or by external geological process like erosion, weathering, deposition, etc. According to rock cycle one rock type can be changed into another (either of other two types). Out of the volume of the outer 16kms of the earth’s crust, 95% is igneous rocks and 5% is made up of sedimentary rocks. Note that here the metamorphic rocks are included either of the category based on their original rock type, that is, if it is from igneous origin then that is considered under igneous rocks
Igneous Rocks
Igneous rocks are the oldest type of rocks in the earth. All the other types of rocks are formed from igneous rocks. Igneous Rock is formed when a magma cools underground and crystallizes or when it erupts unto the surface of the ground, cools and crystallizes. Magma that erupts onto the surface is called lava. Igneous rocks can be sub classified further according to their depth of formation. The rocks that form below the earth surface are called as intrusive igneous rocks. And rocks that form on the earth surface are called extrusive igneous rocks (volcanic rocks). Granite, pegmatite, gabbro, dolerite, basalt are some examples for igneous rocks. When magma cools slowly underground the crystals are large enough to see. When it cools quickly on the surface, the crystals are very small and you would need a magnifier or a microscope to see them.
Sedimentary Rocks
Rocks are broken up in to small pieces due to weathering agents like wind, water, etc. Those small particles are known as sediments. These sediments get deposited by various mechanisms. These sediments form very thin layers. Then these layers become harder over a long period of time. Those hardened layers of sediments are called sedimentary rocks. Texture of sedimentary rocks reflects the mode of sediment deposition and subsequent weathering. Sedimentary rocks are easy to identify as layers are visible. Most sedimentary rocks are formed under the water (sea). Sedimentary rocks normally have pores as they formed from sediments. Shale, sandstone, limestone, conglomerate, coal are some of the examples for sedimentary rocks. These rocks are usually rich in fossils. Fossils are the remains of the animals and plants, being preserved in rocks. Sedimentary rocks are found in a variety of colours.
Notes
Remember that it is illegal (and dangerous) to get out of your vehicle at any place in the Park except at places especially designated and clearly marked to do so. This is a designated site but you still need to be careful!!!
There is an entrance fee to enter the Kruger National Park. Wild Card holders can get in for free.