When in London I notice the hustle and bustle of people rushing about their daily business. This earthcache is designed to make you stop and look closely at your surroundings.
Here at 55 King William Street the facade of the building has been clad in an amazingly beautiful material.
The scientific study of the Earth's structure, composition and processes of formation and evolution is called Geology. Of particular interest to Geologists are rocks - where they came from, how they were formed, etc.
The three main types of rock are:
a) Sedimentary
When small pieces of material are carried along by flowing water and/or the wind, they can become deposited at points where the flow slows down. For example at the entry point into a lake from a river or at the crest of a sand dune. Over time the deposited material accumulates in layers (sediments). The upper layers gradually compact the lower layers and the water is squeezed out in a process called compaction. The squeezed out water contains dissolved minerals and acts as a glue binding the small pieces of rock together. Over millions of years the sedimentary rocks are formed.
Sedimentary rocks have layers and contain grains of material. Fossils may be found where plants and animals have become trapped as the layers settle.
Two common examples of sedimentary rocks are:
- Limestone (which is formed from sediments laid down in warm and shallow waters. The deposits include muds, sands and the skeletons of organisms including corals and molluscs. Limestones come in many colours from dark reds, dark browns and dark greys through to the purest white. Any fossils present are surrounded by grains of other materials such as sand, mud, other fossils and mineral infill.)
- Shale (which is formed from muds and clays. Shales are often grey in colour. They are crumbly because the layers are weakly bonded together and so fall apart easily.)
b) Igneous
The formation of igneous rock can take place in two places: Either inside the Earth where the temperatures are high enough for the rock to remain liquid (This liquid rock is called magma), Or at the surface of the Earth where the magma emerges from volcanoes as lava. When the magma cools down it becomes solid and depending on a number of factors including the speed of cooling it will take different forms and have different visible characteristics.
Igneous rocks have crystals of different sizes but never contain fossils.
Two common examples of igneous rocks are:
- Granite (which forms underground and has larger crystals as it has cooled slowly. Crystals in granite are generally lighter in colour and can include grey-coloured quartz, pink or white feldspars, and black smaller crystals of biotite and other minerals rich in silicates)
- Basalt (which forms during volanic eruptions and has smaller crystals as it cooled quickly in the air or in water. Basalts are dark in colour, sometimes with smaller areas of lighter coloured materials. It is possible that these lighter coloured materials filled ancient gas bubbles that are now preserved in the rock.)
c) Metamorphic
A metamorphic rock is created when an existing rock (igneous or sedimentary) is chemically changed by extreme heat or extreme pressure. It does not simply melt but rather the minerals within it are altered. If the metamorphic rock is formed from a sedimentary rock, any fossils present will not persist as they will be destroyed. Note that metamorphic rocks can also be metamorphosed.
Two common examples of metamorphic rocks are:
- Marble (which is formed from limestone and has a sugary texture. The marble can be of a single colour or have "veins" of a variety of colours)
- Slate (which is formed from shale. Slate can be split into thin hard sheets making it particularly suitable as roof tiles)
Earthcaches have no physical cache to find but there are the following tasks to perform in order that you can log your find
Tasks:
1) Describe the material the facade is made from in terms of colour, texture, the shapes of the distinctive objects within it
2) What 3D shape would the distinctive objects have been? (Note that answers such as "a circle", "a triangle" or "a square" are wrong as these are not 3D shapes).
3) From your observations, which of the rock types Sedimentary, Igneous or Metamorphic do you believe the facade is made from?
4) Optional, take a photo of yourself and/or your GPS in the general area of the EarthCache
Please email or message me your answers via the Message Centre. You are free to log your find once you have contacted me. You don't have to wait for a reply.