Classifying Igneous Rocks
CLASSIFYING IGNEOUS ROCKS An igneous rock is a rock formed by the cooling and crystallization of magma intrusively in the crust or extrusively on the surface. The location and speed of cooling and the type of magma determine which igneous rock is formed. Igneous rocks can be classified according to their colour, texture and density, the minerals present, and the chemical composition of the rock. COLOUR Colour is useful as a diagnostic tool for course-grained igneous rocks but not fine grained. The colour index of a rock indicates the amount of dark ferromagnesian minerals that are present. These include olivine, pyroxene and biotite mica. They are rich in iron and magnesium and usually associated with constructive plate margins. The pale minerals in igneous rocks are called felsic minerals. These include feldspars, quartz and muscovite mica. They are rich in silica and aluminium and associated with continental areas. The colour index measures the proportion of ferromagnesian or mafic minerals present in the rock. Rocks with less than 30% of dark mineral are pale and described as leucocratic. Rocks with 30-60% are mesocratic and tend to be grey in colour. Those with over 60% mafic minerals are known as melanocratic. TEXTURE The texture of a rock describes the relationships between the grains. Grain size, shape and orientation, degree of crystallinity, and the ways in
Can Geologists Save the Planet? Geologists have made many discoveries in the past and continue to today at an ever-increasing rate.
Can Geologists Save the Planet? Definition of Geology - "The science that deals with the earth's physical structure and substance, its history, and the processes that act on it." [1] It cannot be questioned that the science of geology is a very important subject for us to study. By examining the earth's physical structure and chemical 'make up' we can discover evidence for hypothesized past occurrences. Geologists have made many discoveries in the past and continue to today at an ever-increasing rate. To elaborate on the idea of geologists alone saving the world we must look at these past discoveries and the affects that they have had on the world. The first recorded person to discover any geological concepts was Herodotus (500BC). He observed how the Nile deposited silt, but he believed that most features of the earth were formed as a result of short but violent processes. It was not until the 4th Century BC that Aristotle made his observations, that these geological features were in fact the result of change over vast amounts of time. Over time more people contributed to the initial thoughts about the Earth's features, including Eratosthenes who was the first to calculate the circumference of the Earth (in 250 BC); and even Leonardo da Vinci around the 16th Century, who discovered how sedimentary rocks were formed, how they were then uplifted into fold mountains, and
Describe and explain how marine and sub aerial processes have formed the sequence of landforms at Stairhole, Lulworth Cove and Warbarrow bay.
Coastal Landforms Questions Describe and explain how marine and sub aerial processes have formed the sequence of landforms at Stairhole, Lulworth Cove and Warbarrow bay. Lulworth is a classic example of the various forms of coastal morphology. There are a diverse range of features created by both marine and sub aerial processes. The coast is a particularly diverse landscape as it is effected by nearly all types of weathering. Lulworth is particularly famous for four important features, Durdle door, Stairhole, Lulworth Cove and Warbarrow Bay. These three landforms can be viewed in a series of stages of erosion. However before we look at the process which have sculpted the coastline we must first analyse the rock type on which these processes have been working in order to fully comprehend what is happening. Hard Purbeck stone was once the front line of defence against the sea however little now remains. The little that does remain has protected the land sufficiently behind it creating headlands. Also found here are Portland limestone which due to it's massive lithology is also very resistant. The steep angle of dip away from the sea also gives the sea a wall like quality. However behind the Purbeck and Portland softer Wealden Clay and Chalk can be found. The first feature in question Stairhole, has been created by a breach of the outer Portland limestone. This has
Limestone analysis
Limestone Limestone (CaCO3) is a sedimentary rock which is mainly calcium carbonate (mineral calcite). Limestone is made from sea shells and remains of creatures under the sea. It formed millions of years ago. Limestone is a very useful rock and we use a lot of it. 600 tons of limestone is mined in every minute and 120 million tons of it is mined every year. We use 3 1/2 tons of limestone every year. 80% of the quarried limestone is used in construction and 3% is used in agriculture. Limestone has many uses. It is used in construction because is very strong, durable and not too expensive. An average of 50 tons of limestone is used in the building of houses. Some old buildings like cathedrals and many landmarks especially in Europe and North America are often made just from limestone blocks because limestone is easy to cut and carve and it can last a long time, although acid rain can cause them to wear away. Other construction uses of limestone include concrete, cement and steel manufacture, road making, bricks, paint, glass, mirrors, paper and to purify water. Limestone is also used in cosmetics, medicine, toothpaste and it is used to fortify the amount of calcium in bread. Another important use of limestone is to neutralise acid. Limestone is ground into a powder which is used to neutralise acidic lakes caused by acid rain and it is used in farming. Soil is measured using
Rock Collection Science
Sonja Radmilovic Rock Collection Science 9-1 27/4/02 Rocks are composed primarily of minerals and can be an amalgam of different minerals or can be composed of one mineral. Over 3500 minerals have been identified; most of these can be found in the earth's crust. Some of the earth's minerals are exceedingly popular - fewer than 20 minerals compose more than 95% of the earth's crust. There are three different ways rock can be created on earth and thus there are three main classifications of rock, based on the three processes - igneous, sedimentary, and metamorphic. The rock cycle represents the alteration of rock-forming minerals above and below the earth's surface. At the top of the diagram molten rock material, magma, cools (crystallization) to form igneous rocks. If magma is extruded on to the surface it is called lava. Cooling above the surface yields rocks with fine textures, while those that form from slow cooling beneath the surface typically have large crystals. Igneous rock may melt when exposed intense heat to form magma again, or be changed into metamorphic rock. Igneous rocks may also be exposed to weathering, erosion and deposition to form sediment, the precursor for sedimentary rock. As sediments accumulate they are subjected to compaction and cementation to form
Sedimentary Rocks
Sedimentary Rocks Sedimentary rocks are formed from layers of deposits laid down in lakes or seas. Over millions of years the layers of sediment build up resulting in the weight pressing downwards, creating high pressure, which squeezes the water out. As the water is squeezed out, salts form between the particles of sediment due to crystallization and this cements the particles together. Sedimentary rocks can either rise to the surface again to be discovered, or they can descend into the heat and pressure below. Sandstone is a type of sedimentary rock and is formed from sand. Sandstone is fine particles of sand cemented firmly together due to heat and pressure, which is why it looks very much like sand. However, there is red sandstone as well as yellow. Sandstone is commonly used for buildings. Limestone, which can also be called chalk, is formed from seashells. It mostly contains calcium carbonate as seashells are made from calcium carbonate. It is usually white or grey in colour. The original shells are mainly crushed down how some fossilised shells can still be found in limestone. Mudstone, which is also known as shale, is formed from mud. Mud is basically finer particles of sand cemented together due to heat and pressure. Mudstone is often grey in colour and unlike other rocks; it tends to split onto its original layers very easily. Coal is a fossil fuel formed
Compare and Contrast the Weathering Found in an Area of Limestone Country with that Found in an Area of Granite.”
Geography Essay - "Compare and Contrast the Weathering Found in an Area of Limestone Country with that Found in an Area of Granite." Limestone is physically strong and is able to form steep slopes without collapsing, and is composed of calcium carbonate thus making it vulnerable to chemical weathering by carbonation, which dissolves the rock. The rock contains both joints and bedding planes that allow water to penetrate deeply into the rock, and is highly permeable. Water is able to travel rapidly through the limestone and due to its strength is also able to form underground cave systems. Unlike chalk, limestone is a non-porous rock. Areas of limestone have relatively thin soils due to much being dissolved during weathering, and are unable to support much vegetation, for example it is very rare to see trees. This means that bare rock outcrops and scars are a common feature of a limestone landscape. Scars are steep cliffs of bare rock that are vulnerable to weathering processes such as frost shattering and carbonation leading to solution. Limestone is quarried for cement and road stone, and many limestone exposures in the Pennines are due to human activity as much as natural processes. There are many characteristic features of a limestone landscape both on the surface and underground that are the product of weathering. The main weathering processes are carbonation, in which
Dovedale - Limestone rocks.
Limestone rocks are sedimentary rocks (one of the three main rock groups) that are made from the mineral calcite. Limestone rocks are formed at the bottom of lakes and seas with the accumulation of shells, bones and other calcium rich goods. For thousands, even millions of years, little pieces of our earth have been eroded, broken down and worn away by wind and water. These little bits of our earth are washed downstream where they settle to the bottom of the rivers, lakes, and oceans. Layer after layer of eroded earth is deposited on top of each. These layers are pressed down more and more through time, until the bottom layers slowly turn into rock. The heat and pressure causes chemical reaction at the bottom and the rock turns into solid stone, the limestone. Limestone is especially popular in architecture, and many landmarks around the world, especially in North America, Europe, and the pyramids in Egypt are made of limestone. In the 19th and 20th centuries, limestone became very popular in the architecture because limestone was readily available and relatively easy to work with. It is also long lasting and stands up well to exposure. However, it is a very heavy material, making it impractical for tall buildings, and relatively expensive as a building material. Physical Properties of Limestone Hardness 3 to 4 on Mohs Scale (out of 10) Density 2.5 to 2.65 Kg/m3
Footpath Erosion in the Yorkshire Dales National Park
Footpath Erosion in the Yorkshire Dales National Park I decided to look at what is the effect on footpath erosion because of being in a national park. Footpath erosion has become a major problem in the Yorkshire dales, the Yorkshire Dales Park Authority started a project called Three Peaks project which is a counter erosion scheme. The main problem is places at honey spots, which are most frequently used because of the amount of people walking on them this is shown photograph #24. It is shown here that walkers have to walk round the path further adding to the erosion. If Upper Nidderdale were to put in the national park they would suffer these pressures and would have to make additional footpaths that are hard wearing such as the ones in Malham but this would cause a blot on the landscape. One major factor is walker's boots because they kick away and break down the surface but this is by means no means the only factor. It is not only the walkers that cause the erosion the bike and the heavy footfall of fell runners who can also break the ground up. It is not only human impact that makes the footpaths wear down, the livestock has been a primary source of some of the most serious surface on the surface because there feet break down the surface also they eat all the roughage on the surface without this the soil breaks down because there are no roots in the soil to keep the
Wind is an important agent of transport and deposition. It's effectiveness as an eroder remains questionable. Discuss.
Wind is an important agent of transport and deposition. It's effectiveness as an eroder remains questionable. Discuss. A desert can be defined as any region that receives less than 25cm of rain per year where evapo-transpiration equals or exceeds precipitation or in other terms where there is a permanent moisture deficit. Arid areas cover one third of the earth's land surface and there is an enormous amount of variety within in them. Most of these deserts lie in the tropical and subtropical belts between 20o and 30o north and south of the Equator. Wind, as in other physical systems, can erode, transport and deposit but as stated its role as an eroder remains open to discussion. Transport in deserts is carried out in three processes, being suspension, through the air less than 25 metres above ground level; saltation, where grains bounce a few cm above the ground; and surface creep. In suspension very fine material is picked up by the wind, raised to considerable heights and carried great distances. The finer materials are taken away leaving behind a lag deposit. Transport is effective and important here in that in 1km of air, 900 tonnes of sand can be entrained. In some case red dust from the Sahara has been carried northwards and deposited as 'red rain' over parts of Britain and has been found in places as far away as Hawaii. Dust Storms such as the above have increased