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B Barber |
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Science |
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Middle Years Science Program
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Return to Curriculum 
Materials from the Earth: The formation of the Earth happened a long time ago. The most widely accepted model for the beginning of the Universe was the Big Bang Theory in which it suggests that the Earth began with a huge explosion. To date bits and pieces of this explosion are still being thrown outwards into space. Evidence of this can be found by astronomers observing stars and planets that are red and blue shifted (have a tinge of red or blue in them). This suggests they are travelling away from us at incredible speeds. They all appear to be moving outwards from a central point out in space which scientists have identified as the centre of the Universe. To date, no other theory comes close to explaining the Universe like this does. The resulting formation of Earth as a piece of debrise from this huge explosion can then be explained. It is found that the same side of the Moon faces the Earth and always has. This seems to suggest that the Earth and Moon were once one combined piece of space junk from the Big Bang. As the Earth evolved and its surface cooled and formed an atmosphere the inner molten core became burried underneath a hard outer shell called the Earth's crust ...
The crust containing mountains, seas and the rock we dig up is called the lithosphere. Covered by a thin layer of soil and sand is the crust forming a solid shell made mainly from solid rock - ranging from 33km to 11km thick. It is as thick as a postage stamp on a basketball. The crust of the Earth varies between 20 degrees to 500 degrees celcius. The mantle underneath is 280km thick with temperatures close to 3000 degrees celcius. The rock is mainly molten and is the source of volcanic activity and earthquakes. The next layer within the earth is the outer core which is 2300km thick with continually moving iron and nickel. These metals create the magnetic field of the Earth and help protect us from dangerous cosmic rays. The temperature gets up to 6000 degrees celcius. The inner core is 1400km thick getting to temperatures of 7000 degrees celcius. Under the extreme pressure most of the metal in this core are solid. Formation of the Earth The Universe is thought to have begun 20,000 million years ago with the Big Bang theory describing a huge explosion involving all the matter and energy in the Universe. This matter formed the galaxies, stars, gas and dust which is still expanding away from the original explosion. Around 250 million years later, immense condensations of gas (hydrogen and helium) formed, collapsed and in doing so heated up until interior temperatures of more than 1 million degrees celcius caused nuclear reactions to begin. Hydrogen is converted into helium with the release of energy as heat and light. A star was born. For the nexxt 15,000 million years, our Sun and the planets did not exist. The Solar System formed about 4,600 million years ago from a cloud of gas and dust, in the spiral arm of the galaxy. The Universe at that time had much the same appearance as it does now, except that the galaxies were a little closer together. The Earth formed from the accumulation of debree in space with the friction of the collision melting the whole of the Earth. This caused the heavier elements iron and nickel to sink to the centre and the light elements floated to the surface. Rock Classification & Formation: The are different rock formations in the Earth's crust. Rocks formed from particles of sediment are called sedimentary rock. Most sedimentary rock foms from weathered rock which has been exposed due to erosion. Grains of sediment are cemented together to form a solid rock. The process is as follows ...
Sandstone is formed from grains of soil that have been cemented together over a period of time. Mudstone and shale are formed by finer grains of sediment deposited by calm water in the form of mud. Siltstone has grains slightly larger than those of mudstone. Conglomerate contains grains of different sizes which have been cemented together. Limestone is a sedimentary rock that has formed from deposites of the remains of sea organisms, such as shellfish and coral. The hard parts of these dead animals contain calcium carbonate. These deposits are cemented together over time. Coal is formed from the remains of dead plants which are buried by other sediment. In dense forests, layers of dead trees and other plants build up on the forest floor. If these layers are covered with water before rotting is completed, they can become covered with other sediment. The weight of this sediment compacts the partially decaying plant material. Over millions of years the compacting increases the temperature and squeezes out water forming coal. Some sedimentary rock forms when water evaporates from a substance leaving a layer of compressed rock behind. Rock salt for example forms from residue of salt that remains after evaporation of water from lakes or dried up sea beds. Sedimentary rock are often visible in layers in the sides of cliffs. Layers of sedimentary rock push up and are exposed by erosion and other forces. Sandstone and limestone are often used for buildings and are useful for carving. Lime can be used for cement, plaster and for treatment in the garden. Coal can be used for fuel when burnt in powering steam turbines in electric power stations. Igneous rock are those formed from molten rock. Molten rock is magma which upon reaching the Earth's surface is lava. Igneous rock like granite form slowly below the Earth's surface - slow cooling magma produces large crystals which can be easily seen and felt. Other forms like basalt form above the surface when lava cools quickly from a volcano erupting. Deep below the Earth's surface the temperatures are very high. The process of change to rock formation due to high temperatures is called metamorphism forming metamorphic rocks. The change depends on the type of original rock, the amount of heat and pressure on the rock, and the rate of change taking place. Metamorphic rock can be identified by bands or flat leaf-like layers. These bands are evident in the samples of gneiss. Some common examples of the formation of metamorphic rocks:
Types of Rock
Rock Identification Chart
Igneous Rock Identification [65% of rock]
Sedimentary Rock Identification [7% of rock]
Metamorphic Rock Identification [28% of rock]
Where would you find these rocks?
Identifying Minerals and Metals
Minerals and Non-Metals
Uses of Minerals
Composition and Types of Soil: What is soil? It is a complex mixture of minerals and organic matter. The minerals come from the disintegrated rock, the organic matter from decomposed plant and animal matter. Mixed in with this is water, air and numerous living organisms. The main function of soil is to provide plants with nutrients, water, oxygen and anchorage for the root system. Soil is constantly changing. Natural changes include the weather, insects, worms, bacteria and fungi. Adding fertilizer, chemicals and mulch can completely alter soil type. Most soil falls into two categories: heavy or light depending on the amount of clay or silt (fine particles) or sand (coarse particles) they have. Clay is made from very fine particles that pack together closely, thus hindering the downflow of water and air which are both essential for plant growth. Gypsum can break this up and allow the plant to take in water and air. In clay soils in a large downpour, plant root may end up very wet and stay wet resulting in the rotting of tree roots - the spaces between clay particles are filled with water. Sandy soils are light because they are much easier to dig when wet or dry. Sandy soil drains faster but they may dry out too fast.Sany soils must be have rainfall more frequency. They must also be fertilized more often since their nutrients wash away quickly. Loamy soil is half way between the two and is ideal for plants. To identify soil types, follow the steps below ...
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