Quartz & Granite (Lister Park)
Rocks are so common that most of us take them for granted—becoming annoyed when we hit them with the garden spade or taking advantage of them to drive in tent pegs on summer camping trips.
But what exactly is a rock?
To geologists, a rock is a natural substance composed of solid crystals of different minerals that have been fused together into a solid lump. The minerals may or may not have been formed at the same time. What matters is that natural processes glued them all together.
There are three basic types of rock: igneous, sedimentary and metamorphic.
Igneous rocks get their name from the Latin word ignis, meaning "fire." They form from volcanic magma when a volcano erupts and are also referred to as volcanic rocks. Under the surface of the Earth the magna is kept liquid by high temperature and high pressure. As the volcano erupts hot magna reaches the surface. Afterward the lava rapidly cools down and solidifies. The crystals formed by cooling magma are usually small. Magma doesn't always reach the surface. Sometimes it is trapped underground in pockets of other rocks. In this case the magma cools down more slowly forming larger crystals and coarse-grained rocks. How the rocks form will depend not only on the different cooling temperatures of the magma but also its chemical composition. Typically, granite makes up large parts of all the continents.
Sedimentary rocks are formed from eroded fragments of other rocks or even from the remains of plants or animals. The fragments accumulate in low-lying areas—lakes, oceans, and deserts—and then are compressed back into rock by the weight of overlying materials. Most sandstone is composed of quartz or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow, red, grey, pink, white, and black. Since sandstone beds often form highly visible cliffs and other topographic features, certain colours of sandstone have been strongly identified with certain regions.
Fossils are most frequently found in sedimentary rock, which comes in layers, called strata.
Metamorphic rocks are any types of rocks that have been transformed by pressure, heat, or the intrusion of fluids. The heat may come from nearby magma or hot water intruding via hot springs. It can also come from subduction, when tectonic forces draw rocks deep beneath the Earth's surface.
Marble is metamorphosed limestone, quartzite is metamorphosed sandstone, and gneiss, another common metamorphic rock, sometimes begins as granite.
Weathering and erosion.
What is the difference between weathering and erosion?
Weathering is the process of decomposing, breaking up, or changing the colour of rocks. Weathering may be caused by the action of water, air, chemicals, plants or animals.
- Chemical weathering - involves chemical changes in the minerals of the rock, or on the surface of the rock that make the rock change its shape or color. Carbon dioxide, oxygen, water, and acids may all cause chemical weathering.
- Mechanical weathering - is the process of breaking a large rock into smaller pieces without changing the minerals in the rock. Mechanical weathering may be caused by frost, ice, plant roots, running water or heat from the sun..
Once the small pieces of rocks are changed or broken apart by weathering, they may start to be moved by wind, water, or ice. When the smaller rock pieces (now pebbles, sand or soil) are moved by these natural forces, it is called erosion.
So, if a rock is changed or broken but stays where it is, it is called weathering. If the pieces of weathered rock are moved away, it is called erosion.
Many thanks for allowing the EarthCache to be placed to the District Parks Manager (Bradford Wards) Sports and Culture.
In order to claim this Earthcache you will need to answer the following questions and e-mail them to the CO via the link at the top of the page. An optional photo of yourself or GPS device at GZ would be much appreciated.
Examine the rock at the posted co ordinates.
- Explain in your own words how the rock at the posted co ordinates feels to the touch.
- How would you describe the grains that make up this rock? What colour are the grains
- What type of rock do you think this is?
- Describe what can be seen on top of the rock, what colour is it and how far does it protrude from the rock?
- What are the dimensions of the stone at the posted co ordinates?
Visit Waypoint N 53 48.850 W 001 46.594
- Explain in your own words how the rock at the posted co ordinates feels to the touch.
- Describe the colour, shape and size of the crystals on the North facing edge.
- Please describe any signs of weathering or erosion that you can see or feel on this rock
- What type of rock do you think this is?