Rocks

Types of rock

There are 3 types of rock:

Sedimentary
Metamorphic
Igneous

Sedimentary rocks

Sedimentary rocks are made from layers of sediment. They are grainy and crumbly and may contain fossils.
Examples of sedimentary rocks are sandstone and limestone.

Metamorphic rocks

Metamorphic rocks are formed by the effect of extreme pressures and temperatures deep within the Earth.
This alters the structure of the existing rock.
Metamorphic rocks show small crystals in layers (bands).
Metamorphic rocks are hard and smooth.
Examples of metamorphic rocks are slate and marble.

Schists

Schists are formed from basalt (an igneous rock) or shale (a sedimentary rock) that has been pressurised.

Marble

Marble is made from limestone that has been subjected to moderate heat and pressure.

Igneous rocks

Igneous rocks are formed by the solidification of molten material from below the earth's surface.
Extrusive igneous rocks are cooled quickly so small crystals form (e.g. basalt).
Intrusive igneous rocks are cooled more slowly so large crystals form (e.g. granite).

Granite

It was made from molten rock from inside the Earth (actually the mantle). If the magma doesn’t make it out of the crust, but cools down inside the crust it makes granite.
Where the magma intrudes the crust it makes granite intrusions.

Granite Intrusions

A vertical intrusion is called a dyke. If it’s softer than the rest of the rock, it makes a dip called a trench.
If the dyke is harder than the surrounding rock it sticks up leaving a ridge.
If it makes a big, dome-shaped intrusion it is called a batholith.
A sideways intrusion that goes along a bedding plane is called a sill.

Basalt pillars

These pillars were formed when lava cooled on the Earth’s surface.

What is a batholith ?

The top of the granite might be exposed if the rock on top gets eroded away.
Granite is quite hard to erode, so it gets left sticking up.
The top of the batholith isn’t smooth, there are bits that stick up more. These bits are called tors.

What is a tor ?

Granite is a jointed rock (it has small cracks in it). These joints are lines of weakness.
Granite doesn’t get weathered or eroded very easily, but these cracks can be weathered by frost-shattering.
Frost-shattering is when water gets into cracks and then freezes (when it freezes it expands). This forces the joint to get bigger.
A TOR is a rocky peak with expanded joints. Eventually bits break off the tor, fall to the bottom and make a blockfield.

Limestone

Limestone is a sedimentary rock, made by lots of skeletons and shells of sea creatures falling to the bottom of clear tropical seas and getting compacted there.
Made of calcium carbonate (can be dissolved slowly by rain-water or sea water.
Usually jointed – the joints are lines of weakness so they get weathered more.
Quite strong – so it can make steep hills and cliffs without collapsing.

Limestone Features

Swallow Holes
•These happen when a stream dissolves a joint and then flows down it rather than over the ground.
•The hole swallows the stream.

Dry Valleys
•Old river valleys. When there was a lot of water around and the ground was saturated after the last ice age, the rivers flowed over the surface and made these valleys.
•Now the ground isn’t saturated, the water can permeate into the limestone (down swallow holes) and so the valleys are left dry.

Caves
•These happen when the underground stream dissolves an underground hole called a cave.
•Inside caves, the dripping water deposits pure limestone in hanging stalactites and standing stalagmites.

Gorges
•If a cave system (a group of caves) collapses, it leaves a stream in the bottom of a steep-sided narrow gorge.
•Some people think there’s another reason for gorges : powerful rivers of meltwater from the glaciers that melted at the end of the last ice age.

Limestone Pavements
•These are areas where the limestone is exposed. The joints are weathered by solution and this leaves a pattern of dips (enlarged joints called grykes) and flat surfaces (called clints). This looks like a pavement.

Dolines
•These are hollows in the limestone that don’t have a stream going into them. They are formed either by water dissolving the limestone near the surface or by a cave collapsing.

Chalk

It’s a sedimentary rock, a type of soft limestone, it’s made of calcium carbonate.
It was made by lots of shells of sea creatures falling to the bottom of the sea and then getting compacted over the centuries.
Chalk is used in making plaster, putty, cement, mortar and rubber.
Strong types of chalk can be used for building and for blackboard chalk.
Chalk is very porous so it lets water through. This means there aren’t many rivers on chalk but there are dry valleys found on chalk.
Chalk gets eroded mostly by solution (slowly) this is why it tends to stick up above other rocks that have been eroded more quickly.
Chalk doesn’t have joints so it doesn’t make pavements and caves. It tends to make steep cliffs.

Clay

Clay is a fine-grained sedimentary rock. Clay is made from the chemical weathering of other rocks and minerals. It builds up in layers on top of these rocks, or it can be transported by rivers and glaciers and then deposited in lakes and seas.
Clay isn’t strong enough to make steep slopes. It collapses under its own weight. If clay gets wet the water acts like a lubricant and the clay slides downhill, this is called slumping.

Clay is impermeable, this means it doesn’t let water in.
Clay is used for making pots.
It’s also used in paper making, for the tips of spark plugs, in chemical filters and in musical instruments like the ocarina.

@sami perhar

should we prepare those topics which were included in pms 2009 papers?

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ali imraan

rocks all including mmrocks, igneous rock , sedimentary rocks,

weathering
volcanos
earthquake
plate movements
enough
from maps prepare all projections,
weather pattern of south asia
in geography 2 prepare
imptant industries include iron n steel industry
cash crops
determinism n environmentalism

Green House Gases and their Effects Causes Global Worming

Firstly, we need to understand that our atmosphere is a layer surrounding the earth held in place by gravity and primarily made up of Nitrogen (78%), Oxygen (21%), with water and other gases making up the remainder. Scientists now realise that the proportion of these gases has increased significantly over a few hundred years. The real increase began around the time of the Industrial Revolution. This is when we began to burn fossil fuels (coal) in large quantities to power our steam engines.

It is on the 'remainder' that we will focus as it is the concentrations of these trace gases that cause the greenhouse gas problem. The trace gases are made up of Argon, Carbon Dioxide, Neon, Helium, Methane, Hydrogen, Nitrous Oxide and Ozone. Human activities result in emissions of four principal greenhousegases: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and the halocarbons (a group of gases containing fluorine,chlorine and bromine). All these gases have what is known as - Global Warming Potential , or GWP with some much higher than others.



Scientists now realise that the proportion of these gases has increased significantly over a few hundred years. These gases are termed 'green house gases' because during the day the earth absorbs heat from the sun, although much of this is radiated back out into space. The atmosphere surrounding our earth contains these gases, and acts like a blanket keeping some of the heat in. If there weren’t an atmospheric ‘blanket’ we would freeze during the night, like some of the other planets or our moon.



These gases are called greenhouse gases as they effectively make the blanket around our globe thicker, trapping more heat and turning the globe into a green house. (A green house is a structure that market gardeners use to grow vegetables in. It is covered in clear plastic or glass to let the sun light in, and traps the heat inside, increasing the temperature. Sometimes these are also referred to as 'hot houses').

This is where it gets a bit frightening! The fossil fuels we are burning in ever-increasing amounts contributes to higher concentrations of methane, carbon dioxide and nitrous dioxide, effectively turning up the heat and turning the globe into a veritable greenhouse

Effects

Here aresome of the effects of the Earth becoming a 'green house'
Land and ocean temperatures rise
North and South Poles (Arctic and Antarctic) melt
Glaciers melt
Ocean currents change
Weather patterns change
Sea levels rise (due to oceans warming the water 'swells' and from increased water as polar regions melt

So What!

Well, I wish we could simply say that! However turning the globe into a green house has dire consequences for all of us. We already experiencing heatwaves associated with land temperature increase and thousands of people will die through future heatwaves. (In the 2003 heatwaves in France over 20,000 people died).

Droughts will become more prolonged and be even more devastating than anything we have experienced. This is because higher temperatures evaporate water from the land, which will also give rise to more wildfires. Agriculture and food crops will be devastated in some regions and diseases like malaria and dengue fever will increase as conditions favourable to these diseases spread.

Higher ocean temperatures increase the power in cyclones and hurricanes, (stimulating more tornadoes ) and we will see a higher frequency of severe storms (like Hurricane Katrina)and associated flooding that will do extraordinary damage to infrastructure, and destroy houses, towns and villages. This is already driving up insurance costs.

Rising sea levels will displace millions of people, (already on some Islands people are being moved off due to rising seas) and the geography of the land will change dramatically, with millions needing to be relocated along with loss of buildings.

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Golden words for my life: you must be proud of kudos associated with all these awards.

ROCKS

There is a great variety of rocks. There are varied in their mineral composition, colour, texture, permeability and grain size. The three main types are categorized under :

• Igneous rocks
• Sedimentary rocks
• Metamorphic rocks

IGNEOUS ROCKS

- rocks that are formed by the cooling and solidification of molten rock.

Formation
When a volcano erupts, molten rock called magma is ejected onto the Earth’s surface. Crystallization, a process in which the magma cools and solidifies forming mineral crystals called igneous rocks.

Size of the rocks
depends on the rate at which the molten rock cools. (The longer the cooling, the larger the crystal formed. )

• Magma within the rock cools much slower than the one ejected onto the Earth’s surface. This is sobecause the temperatures inside the Earth are high. Therefore, the igneous rocks on Earth are smaller.

Features

• Crystalline appearance as they are made up of mineral crystals. <coarse-grained or fine-grained depending on the rate of cooling>
• Coarse-grained igneous rock e.g. granite.
• Made up of minerals, quartz, feldspar and mica. The quartz is grayish and glassy in appearance while feldspar is mostly white. Mica is black and shiny and are in smaller quantities than quartz and feldspar.
• Fine-grained igneous rock e.g. Basalt .
• Consist of feldspar and a high proportion of dark coloured minerals such as olivine and pyroxene which the rock a dark appearance.

SEDIMENTARY ROCKS

- Rocks that are formed by the compaction of sediments or by the crystallization of the dissolved minerals.

Formation
COMPACTION
Sediments such as rock particles & remains of living things are deposited in the sea by rivers and waves. These sediments accumulate layer by layer, over thousands or millions of years, forming thick deposits on land or on the sea floor. The weight of the overlying sediments compact those below. Over time, they form sedimentary rocks. e.g. Sandstone & shale

CRYSTALLIZATION
Sedimentary rocks usually occur in shallow parts of the sea or in lakes in desert areas where evaporation is higher than precipitation. As evaporation takes place, water is lost and the dissolved minerals form crystals. As evaporation continues, more crystals form and accumulate on the sea or lake floor, becoming sedimentary rocks. e.g. coal

FEATURES

• They have a layered appearance because the materials that form them are deposited in layers.
• Plant and animal fossils can be found in many sedimentary rocks,
• Sedimentary rocks (compaction) contain rock particles such as pebbles and sand.
• Sedimentary rocks (crystallization) have crystalline appearance.

METAMORPHIC ROCKS
-rocks that are changed into a different one by great heat or pressure

FORMATION
Metamorphic rocks are formed when existing rocks are changed from their original state by great heat and/or pressure. There is a change in the chemical composition and physical structure of the existing rocks. e.g. marble and quartzite.

FEATURES

• Crystalline appearance
• A banded or layered structure
• Metamorphic rocks are hard and strong.

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Golden words for my life: you must be proud of kudos associated with all these awards.