Welcome to part of the historic quarter of Carlisle. The buildings around you are very typical of this part of the region and demonstrate the skills and knowledge of our forebears in creating the city, hundreds of years ago.
What is Sandstone?
Sandstone is one of the most common types of sedimentary rock and is found throughout the world. It is often mined for use as a construction material as it is easy to work with and can be carved into decorative shapes. It is composed of sand-sized particles of mineral, rock or other organic material ranging in size from 1/16 millimeter to 2 millimeters in diameter. Sandstone also contains a cementing material that binds the grains together and may also contain silt or clay particles that occupy the spaces between the sand grains
The individual grains within the stone have been reduced to "sand" size by weathering and have been transported to their depositional site by the action of moving water, wind or ice. The time and distance of transport may be brief or significant and during that journey the grains are impacted by chemical and physical weathering. If the sandstone is deposited close to its source rock, it will resemble the source rock in composition and colour. However, the more time and distance that separate the source rock from the final deposition site, the greater its composition will change during transport.
Mineral grains in sandstones are usually quartz or feldspar. Sometimes the quartz content of the sandstone can be very high. This is because quartz is very durable and less subject to destruction during the sedimentation.
What is Granite?
Granite is the best-known type of igneous rock. Many people recognise granite easily because it is the most common igneous rock found at the Earth's surface and is used to make many objects that we encounter in daily life, such as work tops, plinths, floor tiles, paving stones and cemetery monuments.
Granite is predominantly composed of quartz and feldspar with minor amounts of mica, amphiboles and other minerals. This mineral composition usually gives granite a red, pink, gray or white colour with dark mineral grains visible throughout the rock. It is formed from the cooling of magma below the Earth’s surface into crystals. If the magma cools quickly, a lot of small crystals are formed. Longer, slower cooling creates fewer, larger crystals in the rock.
Granite is an abundant rock and is hard enough to resist most abrasion or weathering, is strong enough to bear significant weight and can polished to a high sheen. These characteristics make it a very desirable and useful stone. Although it costs more than many man-made building materials it is frequently selected because it gives results that are elegant, durable and of lasting quality.
There are four activities for you to undertake to complete this Earth Cache. Please don't post the answers in your log but send me an email with your answers.
1. Look at stones that make up the Cathedral buildings, especially the ornate features around and above the windows. Using your knowledge of igneous and sedimentary rocks, state what type of rock has been used to build the cathedral and describe the colour and texture of the stones. Give an approximate size of the largest stones used at the base of the building, above the decorative covings.
2. Cross over Castle Street to look at the 3 sets of benches forming the Triptych art installation. They have carved illustrations that depict both the social and natural history of the area. Touch the surface of the benches and examine the size of the grains in the rock. Using your knowledge of igneous and sedimentary rocks, state what rock the benches are made of, describing their colour and texture. Estimate the size of the benches and explain what the size of the grains in the rock tell you about the formation of these particular blocks?
3. Comparing the materials used to build the Cathedral and create the benches, explain why the specific rocks were chosen for their particular purpose. Provide a suggestion of where these rocks may have been sourced from
4. If possible, please take a photograph of yourself with your GPSr sitting on one of the Tryptich benches with the Cathedral in the background.