Middle Years Science Program

 

1. Earthquakes (How Stuff Works)
2. Cyclones (How Stuff Works)

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 ...

Sediment is laid down by ice, wind or water in horizontal layers called beds.
Within each bed, the sedimenr grains are squashed together so that they are in close contact.
Water seeps in between the grains, bringing with it many dissolved chemicals.
When the water evaporates, these chemicals are left behind as crystals around the edges of the grains. These crystals cement the grains of sediment together to form rock.

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.

Weathering:

Look around at the landscape in your area. Whether you see mountains, plains, river valleys, coasts, islands, lakes or ocean, what you see is the product of the constant changing of the Earth's surface.

Mountains are pushed up from the plains. Islands form. New land is created by volcanic action, caused by the collision of tectonic plates and by the uplift of shallow sea beds. Over thousands and millions of years, the twin processes of weathering and erosion will flatten the mountains, extend the plains and wash the highest peaks back to the ocean floor.

What is weathering? Weathering is the constant wearing away and the decomposition of the Earth's surface. Rain, wind, ice, plants, animals, the temperature and chemicals all play a part in breaking down the rocks into smaller particles which form the basis of soil. There are two categories of weathering; mechanical weathering and chemical weathering. Each involves different mechanism of weathering.

Mechanical weathering: Mechanical weathering involves the breakdown of rock to smaller pieces by mechanical or physical means. The main types of mechanical weathering are:

Ice wedging: If the air temperature drops below the freezing point of water, any water caught in a crack in a rock will expand upon freezing. This can cause the rock to crack even more and can even break off large chunks of rock starting the process of erosion.

Temperature change: The Sun warming up the surface of a rock will make the rock's surface expand. The underlying rock remains cold and does not expand. At this point, the surface rock may split from the underlying rock, making it vulnerable to further weathering and erosion.

Plants and animals: The growth of plant roots in cracks in the rock and animals burrowing around the rocks, allows water to enter the rock and it surrounds again making the rock vulnerable to further weathering and erosion. Both these processes accelerate the breakdown of rock surfaces.

Water: Rivers and streams carrying small rocks and mud act as abrasives on rock surfaces, wearing away the rocks in their path.

Wind: Wind carries sand which can impact surface rocks and sand blast them forming more sand and dust.

Chemical weathering: Changes in the chemical composition of a rock will often weaken it structurally, making it more vulnerable to mechanical weathering. Chemical weathering occurs when air, water or acids react with rock to change its chemical composition. The main types of chemical weathering are:

Water: Rain falling on a new rock surface will remove some elements from the minerals forming the rock. This process, known as "leaching", can dramatically alter surface rock, allowing it to become more prone to mechanical weathering.

Oxidation: Iron left out in the weather soon rusts. Other elements within the rock minerals will also react with oxygen in the air, quite often forming water-soluble minerals that can then leach away.

Carbonation: Rainwater combines with carbon dioxide in the air to form a weak acid known as carbonic acid. This acidic solution is particularly effective in weathering limestone and marble. Some limestone caves and sinkholes are thought to have been formed by the constant action of carbonation over thousands and millions of years.

Plant acids: Some plants and fungi produce acids that dissolve the surface of rocks and minerals to help their roots gain a hold in the rock.

Acid rain: Acid rain has been a part of the environment for about 4.5 billion years. Before the industrial age, it was a result of the interaction between sulfur from volcanoes and water in the atmosphere and in rivers and oceans. The industrial age has brought with it an increase of acid rain, now produced by sulfur dioxide being released when coal and oils are burnt. Acid rain can be a very strong acid, killing fish and accelerating the destruction of man made monuments and rock alike. The strong acids dissolve elements from minerals in the rock, altering the surface of the rock in much the same way.

Once weathering has weakened the structure of rocks, the process of erosion can now take place. Weathering structurally weakens the rocks, while erosion removes and transports the weathered material.

Erosion:

Once rocks have been broken down by mechanical and chemical weathering, the resulting particles are now smaller, and able to be picked up and transported. The process of picking up and moving weathered rock materials is called erosion. The process of dropping these materials in a new place is called deposition.

Erosion occurs when rock particles are moved by an external force or agent. The agents of erosion are ice, water, wind, waves and gravity. The degree to which erosion occurs depends on the slope of the land, amount of rain or snow, wind and looseness of the rock and soil. The hills of Australia no longer erode quickly, but the steep mountains in the New Zealand Fjord country tend to erode very quickly. On the slopes of Mt. Cook, New Zealand, you can hear the mountains eroding as rocks slip and roll down the steep sides of the glacial valleys. The five agents of erosion will now be further investigated.

Gravity: Whether a whole mountain side moves slowly or a landslide occurs quickly and dramatically, the mass movement of rocks and soil under the influence of gravity can remove large amounts of material from a mountain side. Often associated with rain, which weakens a slope, gravity is an important agent of erosion in high steep mountains.

In areas which have been cleared of trees, land movement becomes a real threat. The foothills of the Himalayan mountains of India and the Andes in South America both have large populations trying to cultivate the steep hill sides. In recent years, huge mud slides have caused mass destruction of villages and the flooding of low land areas. Authorities are now working to stop the threat of land slides by reforestation and the ban on removal of trees from these areas.

Water erosion: Rain falling on bare soil on a slope can result in the soil breaking free from the underlying rock and flowing downslope, carrying mud and rock within a mud flow. From the peaks of the mountains, running water forms streams in gullies and canyons. Water is the most important agent of erosion in wet highland areas, quickly moving large quantities of material into lower river valleys and plains.

The removal of trees and their replacement with agriculture has lead to a significant increase in the loss of topsoils in Australia via water run off. Planting of trees around water ways and in areas of high risk from water erosion and better farming practices can significantly decrease the amount of soil lost to water erosion.

Ice erosion: In colder regions, where snow is the predominant form of precipitation, glaciers are the most important agent of erosion. The action of ice, although slow, can be dramatic. The heavy, slow moving ice carries rock, pebbles and sand, which is then trapped within the ice. These trapped rocks ground away at the base and sides of the glacial valley like gigantic sand paper.

During the last ice age, glaciers flattened whole mountains in Tasmania, leaving behind the large lakes of the Tasmanian Western Highlands. On the South Island of New Zealand, steep sided valleys have been formed by glaciers with cliffs hundreds of metres high.

Wind erosion: In dry areas, wind becomes the primary agent of erosion. Sand storms and wind are responsible for the movement of finer dust and sand producing the dominant features of desert landscapes; plains, dunes and sculptured rock outcrops. Over many parts of Australia, the agricultural practice over the last 200 years has involved the removal of many trees from arid regions. This exposes the soil to the wind and increases the chance of dust storms occurring, like the one that occurred over Melbourne in 1983.

Wave erosion: A visit to any beach with a cliff will soon attest to the power of waves as agents of erosion. Coastlines are continually being sculptured and shaped by the action of waves. The Twelve Apostles in Western Victoria with their cliffs, stacks, arches and caves are the classic example of a landscape created by wave erosion. These structures are formed as softer rock is eroded away more quickly than harder sections leaving some parts out in the ocean as the cliff lines slowly recede under the pounding of the waves.

After weather and erosion have affected the landscape, the next step is deposition, as the eroded and transported material comes to rest.

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:

Shale (sedimentary)	--> under pressure -->	Slate
Granite (igneous)	--> under pressure -->	Gneiss
Sandstone (sedimentary)	--> mainly heat -->	Quartzite
Limestone (sedimentary)	--> mainly heat -->	Marble

Types of Rock

Igneous	Sedimentary	Metamorphic
granite	conglomerate	slate
pegmatite	breccia	schist
adamellite	sandstone	gneiss
porphyry	tillite	quartzite
aplite	shale	marble
rhyolite	mudstone	amphibolite
rhyodacite	chert	hornfels
pumice	diatomite	phyllite
tuff	limestone
obsidian	dolomite
syenite	coal
diorite	siltstone
gabbro	flint
dolerite	greywacke
trachyte	jasper
andesite
basalt
serpentinite
ignimbrite
kimberlite
granoldiorite

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?

Igneous	Sedimentary	Metamorphic
basalt - Phillip Island, Berwick, Pakenham	shale - Wellington Rd; Stud Rd cutting	slate - Chewton
scoria - Mt Leura (Camperdown), Mt Eccles	mudstone - Studley Park	schist - Belgrave South
rhyolite - Rocklands Reservoir (Grampians)	siltstone - Kinglake	gneiss - Bindi, Ensay
granite - Arthurs Seat, Strathbogie, Cape Woolamai (Phillip Island)	sandstone - Black Rock, Flowerdale, Mansfield, Grampians	marble - Monumental Mason
granodiorite - Mt Martha, Lysterfield, Harcourt	gypsum - Mildura	hornfels - Lysterfield (Wellington Rd & Summit Rd)
tuff - Mt Leura (Camperdown), Tower Hill (Warrnambool)	limestone - Lilydale, Buchan
	brown coal - Latrobe valley
	black coal - Wanthaggi

Identifying Minerals and Metals

Mineral	Metal	Physical Characteristic
Hematite	Iron	earthy, dull red powder and streaky
Galena	Lead	Metallic, shiny, silvery cubes
Sphalerite	Zinc	Metallic, shiny silver/grey crystals
Cassiterite	Tin	Shiny, black grainy crystals
Chalcophyrite	Copper	Metallic, shiny light yellow
Pyrite	Iron	Metallic, silvery/gold crystals often in cubes
Azurite	Copper	Shiny, dull blue crystals
Malachite	Copper	Shiny, dull green crystals
Bauxite	Aluminium	Earthy, dull, orange pink to light brown spheres
Gold	Gold	Soft golf flakey crystals.

Minerals and Non-Metals

Mineral	Physical Characteristic
Quartz	White to coloured glassy crystals
Calcite	Clear to white crystals, fizzes with hydrochloric acid
Gypsum	White to pink crystals of various shapes
Muscovite	Shiny silver or clear sheets
Biotite	Shiny black sheets
Feldspar	Pink or white crystals

Uses of Minerals

Mineral	Uses in Health, Energy, Communication & Shelter
bauxite	antacids precision surgical equipment containers power lines housing components silver paint
cobalt	animal feed pigments super conductors magnetic alloys
copper	supplements desalination plants wire plumbing roofing
gold	surgical procedures electronics signwriting lettering photography store of wealth heat reflector
zinc	dietary supplements sunscreens sheet metal pipes wire galvanising plumbing
Chromium	stainless and heat resistant steel glass bricks paint ink
lead	radiation for shielding sound proofing glass paint electrical uses TV glass ceramics

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 ...