An accessible EarthCache that will take you to four monuments in Sowerby and also give you a little geology lesson.
To claim this EarthCache, (first) please send your answers for tasks 1, 2, 3 and 4 to me using the Geocaching 'message this owner' link and then (second) log your find. You don't need any additional permission to log. Please upload photos if you have taken any.
Logs without an accompanying message containing correct answers will be deleted! Logs containing the answer will be deleted!
Types of Rocks
There are three types: Igneous, Metamorphic and Sedimentary.
Igneous rock is formed through the cooling and solidification of magma or lava. Examples of this are granite and basalt.
Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means "change in form". The original rock is subjected to heat and pressure, causing profound physical and/or chemical change. Examples of this are marble and slate.
Sedimentary rocks are formed by the deposition and subsequent cementation of that material within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle in place. The particles that form a sedimentary rock by accumulating are called sediment. Examples of this are sandstone and limestone.
A few common rocks and identifying features
Basalt is a dark igneous rock, and is made up of fine crystals, because it cooled rapidly after it came out of a volcano. Basalt does not contain any bedding planes. It is unsuitable for buildings since it is very hard and difficult to fashion into blocks for building, it can however be used more crudely for building simple walls.
Granite is an igneous rock made up of noticeably different crystals of different coloured minerals. Granite may contain crystal structures of different sizes. It cooled slowly below the surface. You won’t be able to identify fossils because it forms from the cooling down of molten material, therefore never contained organisms in it. It doesn't contain any bedding planes as it formed from cooling magma. This is very good building material since it has no linear weaknesses.
Marble is a metamorphic rock. It is formed from limestone that has been subjected to intense pressure underground due to tectonic movement or through being subject to extreme heat. This rock is generally white with different coloured veins running through it. It is a very tough rock and would feel very smooth even after years of exposure to the elements.
Slate is a metamorphic rock. It is a fine grained rock of sedimentary origin. It is waterproof and extremely durable, Slate occurs in a variety of colours from pale to dark. Due to its durability it has often been used for tombstones and memorial tablets.
Limestone is a sedimentary rock. A common building material, especially in ancient times due to the decorative look of the rock and its propensity to being easily carved. This is often a light coloured rock, but other limestones may be variously coloured including darker colours which suffers from chemical weathering, as a result of acid rain. It may contain bedding planes and many varieties of fossils including corals, shells and marine life.
Sandstone is a sedimentary rock; it can be any colour. You may be able to identify the bedding planes which are lines that run all the way through the rock, where different seasons or catastrophic events have altered the composition of the deposits for a short time. The rock will be quite durable but feel rough to the touch and small grains will come off when you rub it vigorously.
Physical weathering
Physical weathering is caused by physical processes such as changes in temperature, freezing and thawing, and the effects of wind, rain and waves.
Temperature changes: When a rock gets hot it expands a little, and when it gets cold the rock contracts a little. If a rock is heated and cooled many times, cracks form and pieces of rock fall away. This type of physical weathering happens a lot in deserts, because it is very hot during the day but very cold at night.
Wind, rain and waves: Wind, rain and waves can all cause weathering. The wind can blow tiny grains of sand against a rock. These wear the rock away and weather it. Rain and waves lashing against a rock can also wear it away over long periods of time.
Freeze-thaw: Water expands slightly when it freezes to form ice. This is why water pipes sometimes burst in the winter. The formation of ice can also break rocks. If water gets into a crack in a rock and then freezes, it expands and pushes the crack further apart. When the ice melts later, water can get further into the crack. When the water freezes, it expands and makes the crack even bigger.
Chemical Weathering
Chemical weathering occurs when the minerals within the rocks are chemically altered. In the process of carbonation, rainwater and carbon dioxide in the atmosphere combine to form carbonic acid. This carbonic acid dissolves minerals within the rock, weakening the structure and resulting in damage and wear. On monuments this can also result in the appearance of staining on the surface.
The monuments in Sowerby
At the posted coordinates you will find Sowerby War Memorial and (on the outside of the churchyard wall) three plaques that commemorate royal events.
The monuments are made from two different rocks and the EarthCache will compare and contrast them and their properties.
Questions
Look carefully at the colour, texture and general appearance of the monuments.
The three plaques were made from one type of rock and the war memorial from a different type of rock.
1. What rock do you think each monument is made from?
2. Explain how you identified the two rock types. Describe your observation in terms of colour, structure and any other identifying features.
3. Why do you think these materials were used?
4. Compare the conditions of the monuments, can you find any evidence of the effects of weathering? Do you think this is physical or chemical weathering? Explain your conclusions.
5. Using your knowledge of these rocks, what is your prediction of the condition of each monument in future years?
6. In your opinion have the designers chosen suitable materials and finish for the monuments? Explain your conclusions.
7. (Optional) Post a photograph in your log of yourself with GPS (or just your GPS) in front of the war memorial.