Rock is often covered by soil or water. It is beneath the oceans, lakes, and rivers of the earth, and under the polar icecaps. Petrology is the scientific study of rocks.
Rocks are classified by their minerals and chemical make-up. The processes that formed them are also noted. Rocks may be igneous, sedimentary and metamorphic. Rock types may change in a so-called 'rock cycle'.
Igneous rocks are formed when molten magma cools, either above or below the surface. They are divided into two main categories: plutonic rock and volcanic rock. Plutonic or intrusive rocks are made when magma cools and crystallizes slowly within the Earth's crust (example granite). Volcanic or extrusive rocks result from magma reaching the surface either as lava or ejecta (examples pumice and basalt).
Sedimentary rocks are the most common rocks on Earth. They form at or near the Earth's surface. Sedimentary rock is formed in layers which were laid down one by one on top of another. Some of the layers are thin, some are thick. Layers are made by deposition of sediment, organic matter, and chemical precipitates. Deposition is followed by squeezing of sediment under its own weight, and cementation. This process is called 'consolidation': it turns the sediment into a more or less hard substance.
The approximate amounts of different kinds of sedimentary rock are:
Only sedimentary rocks have fossils.
Metamorphic rocks are formed by rocks coming under great pressure and high temperatures. These temperatures and pressures are found under mountains and volcanoes, especially when continental plates move together. These conditions change the make-up of the original minerals.
Rocks have had an impact on human life. They have been used by humans for over two million years. The mining of rocks for their metals has been one of the most important things in human advancement. Rocks are mined for building materials of all kinds.
15 (number)
Fifteen is a number. It is between fourteen and sixteen, and is an odd number. It is divisible by 1, 3, 5, and 15.
In Roman numerals, 15 is written as XV.
16 (number)
Sixteen is a number. It comes between fifteen and seventeen, and is an even number. It is also the 4th square number, after 1, 4, and 9.
In Roman numerals, 16 is written as XVI.
Weathering
Weathering is the breaking down of Rock (geology) rocks, soil and their minerals through direct contact with the Earth's atmosphere, waters, or living things. It is a natural process.
Weathering occurs in one place with little or no movement, and should not be confused with erosion which is when rocks and minerals are moved to another place by ice, water, wind or gravity.
Mechanical or physical weathering is when the rocks and minerals are broken down but the Chemical composition remains the same. Mechanical weathering physically breaks up rock.
Wind can blow water or small particles such as sand against the rock thus breaking it down.
The wind blowing over your skin removes body heat.local winds are the winds that blow over short distances.
Rain is another force that works slowly. The force of raindrops on some rocks make them wear down. Rain also can make a chemical change in some rocks, because it is usually slightly acidic. The water mixes with the minerals in the rock to break it down.
Changing temperature can make a rock crack. Every day when the sun shines on the rock, its surface is heated. Heat causes the surface to expand (get bigger) a little. The inside of the rock, though, does not heat up as fast as the outside of the rock. The inside of the rock stays cooler. At night, the surface cools down and contracts. The expanding and contracting makes some places on the surface weak, and a crack is made.
Also, if water gets into a crack in a rock and the temperature goes below the freezing point, the water will freeze and expand. After some time, the rock may be weak enough to break into pieces.
Ice, which can be miles thick, grinds the surface of the rock below it. The particles are carried with the ice, and if a glacier ends up in the sea, so does all the material carried with it.
Lava or magma can cause weathering when molten rock touches older rock. It causes the older rock to change form to a different crystal structure.
Chemical weathering is the breaking down of rock which changes the chemical composition.
The carbon dioxide cycle is the most important for weathering. CO is put into the atmosphere mostly by volcanoes, and it is taken out of the atmosphere by photosynthesis, and by one other process.
While it is in the air, CO can dissolve in water droplets to form weak carbonic acid.
When rain hits rock it does so with mechanical energy and dilute acid. The acid dissolves many types of minerals and rocks though, of course, very slowly. When a mineral like feldspar is dissolved, it lets sodium ions into the sea; chlorine ions come from other minerals. The sea tastes salty because of the elements which have been dissolved out of rocks.
Recrystallisation
Recrystallization (see also crystallization) is an essentially physical process that has meanings in chemistry, metallurgy and geology.
In chemistry, recrystallization is a procedure for purifying compounds. A crystal compound often has other compounds on it that make it less useful. To get rid of these extra items, the crystal is placed in a boiling liquid. Soon the crystal dissolves. The boiling solution, or the mix of the liquid and the dissolved crystal, gets colder. The crystal will form again. The unwanted compounds stay in the solvent, or the liquid. Now the crystal is pure and made of only the compound. Each type of compound works best in a certain type of liquid. Sometimes two or more liquids mixed together are needed to dissolve a crystal.
In geology, solid-state recrystallization is a metamorphic process that occurs under situations of intense temperature and pressure where grains, atoms or molecules of a rock or mineral are packed closer together, creating a new crystal structure.
Limestone is a sedimentary rock that undergoes metamorphic recrystallization to form marble, and clays can recrystallize to muscovite mica.
In metallurgy, recrystallization is the nucleation and growth of new undeformed grains in a deformed metal.
For ice, recrystallization means the growth of larger crystals at the expense of smaller ones. Some biological antifreeze proteins have been shown to inhibit this process, and the effect may be relevant in freezing-tolerant organisms.
Wildlife and Countryside Act 1981
The Wildlife and Countryside Act 1981 is an law for environmental conservation made by the Parliament of the United Kingdom. It protects native species and restricts the release of non-native species into the wild. The Act is split into four parts. Killing most mammals and almost all birds is illegal in the United Kingdom, except for certain types and for certain reasons.
General licences under the act to hunt birds are issued each year by the Department for Food and Rural Affairs (DEFRA) in England. The Department can give a licence to kill or disturb birds. It also gives out a general licence. This allows any "authorised person", that is someone who has the landowner's permission, to kill certain birds, or to destroy their eggs or nests, if there is no other way to get rid of the birds.
This table shows the name of the bird, and the reasons () that type of bird can be destroyed.
or to prevent serious damage to livestock or damage to foodstuffs for livestock, crops, vegetables, fruit, growing timber, fisheries or inland waters.
Soil classification
Soil classification means that one finds categories of soils that are based on general characteristics as well as criteria that decide about the use that is possible.
Soil classification can be approached from both the perspective of pedogenesis and from soil morphology. But in both cases interpretations do not vary widely.
Manor house