EXPLANATION TEXT

Social Function: To explain the processes involved in the formation or working of natural or sociocultural phenomena.
Generic Structure
• A general statement to position the reader
• A sequenced explanation of why or how something occurs.
Significant Lexicogrammatical Features
• Focus on generic, non-human Participants
• Use mainly of Material Processes and Relational Processes
• Use mainly of Temporal and causal Circumstances and Conjunctions
Definition and purposes of Explanation
Explanation is a text which tells processes relating to forming of natural, social, scientific and cultural phenomena. Explanation text is to say 'why' and 'how' about the forming of the phenomena. It is often found in science, geography and history text books.

Generic structure of Explanation
General statement; stating the phenomenon issues which are to be explained.
Sequenced explanation; stating a series of steps which explain the phenomena.

Language Feature of Explanation
1. Featuring generic participant; sun, rain, etc
2. Using chronological connection; to begin with, next, etc
3. Using passive voice pattern
4. Using simple present tense

Explanation text in some way is similar to procedure text. Explanation passage often make description about how something happens or why the thing occurs. While procedure text bring the instruction on how to make something happen completely. The following example of explanation text about how rain happen is best showing on what is explanation text, what is the purpose or social function of explanation text and how it differ from other text types. Explanation text often use technical terms related to the thing which is being explained. Explanation text is commonly compose in the mode of simple present tense.

Examples of explanation text
1. Tsunami
The term of “tsunami” comes from the Japanese which means harbour ("tsu") and wave ("nami"). A tsunami is a series of waves generated when water in a lake or a sea is rapidly displaced on a massive scale.

A tsunami can be generated when the sea floor abruptly deforms and vertically displaces the overlying water. Such large vertical movements of the earth's crust can occur at plate boundaries.

Subduction of earthquakes are particularly effective in generating tsunami, and occur where denser oceanic plates slip under continental plates.


As the displaced water mass moves under the influence of gravity to regain its equilibrium, it radiates across the ocean like ripples on a pond.

Tsunami always bring great damage. Most of the damage is caused by the huge mass of water behind the initial wave front, as the height of the sea keeps rising fast and floods powerfully into the coastal area.
(simplified from www.panda.org)

2. How Venus Eclipse Happens

On May 16, 2010, people in most regions in the world have seen a very rare natural phenomenon. It was Venus eclipse. It was very rare amazing natural event. It was reported that the Venus eclipse will seen again in the future in 2050. Do you know how this rare Venus eclipse happens?

Well, actually Venus eclipse is like Sun eclipse. Venus eclipses occurs when the position of the earth, moon and Venus is parallel. Venus planet will slowly disappear for a moment because it is covered the surface of the Moon. Venus planet seems to move to the back side of the Moon.

The moon and planets are sharing a similar apparent path in the sky. That is why, it is not unusual for the moon to appear to pass close to Venus. In fact, the moon appears somewhere near it about once a month. However, most people don’t see these events because they are visible in the evening sky only half the time, and then only for a short period after sunset. The apparent closeness varies from month to month as well.


3. How does Rain Happen?
Rain is the primary source of fresh water for most areas of the world, providing suitable conditions for diverse ecosystems, as well as water for hydroelectric power plants and crop irrigation.

The phenomenon of rain is actually a water circle. The concept of the water cycle involves the sun heating the Earth's surface water and causing the surface water to evaporate. The water vapor rises into the Earth's atmosphere. The water in the atmosphere cools and condenses into liquid droplets. The droplets grow until they are heavy and fall to the earth as precipitation which can be in the form of rain or snow.

However, not all rain reaches the surface. Some evaporates while falling through dry air. This is called virga, a phenomenon which is often seen in hot, dry desert regions.
Source:
http://mypages.iit.edu/~smart/abduima/lesson2.htm
http://en.wikipedia.org/wiki/Rain

4. How Earthquakes Happen

Earthquake is one of the most destroying natural disasters. Unluckily it often happens in several regions. Recently a horrible earthquake has shaken West Sumatra. It has brought great damages. Why did it occur? Do you know how an earthquake happens?

Earthquakes are usually caused when rock underground suddenly breaks along a fault. This sudden release of energy causes the seismic waves. It make the ground shake. When two blocks of rock or two plates are rubbing against each other, they stick a little. They don't just slide smoothly. The rocks are still pushing against each other, but not moving. After a while, the rocks break because of all the pressure that's built up. When the rocks break, the earthquake occurs.

During the earthquake and afterward, the plates or blocks of rock start moving, and they continue to move until they get stuck again. The spot underground where the rock breaks is called the focus of the earthquake. The place right above the focus is called the epicenter of the earthquake.
Mainly taken from: www.geo.mtu.edu/UPSeis/why.html

5. Cancer

What is cancer? It is actually a group of more than one hundred separate diseases. Most of us are fear from cancer It is reasonable because next to heart disease, cancer is the second leading cause of death.

Cancer cells come from normal cells because of mutations of DNA. Those mutations can occur spontaneously. The mutations may be also induced by other factors such as: nuclear and electromagnetic radiation, viruses, bacteria and fungi, parasites, heat, chemicals in the air, water and food, mechanical cell-level injury, free radicals, evolution and ageing of DNA, etc. All such factors can produce mutations that may start cancer.

Cancer cells are formed continuously in the organism. It is estimated that there are about 10,000 cancer cells at any given time in a healthy person. Why do some result in macroscopic-level cancers and some do not? First, not all damaged cells can multiply and many of them die quickly. Second, those which potentially divide and form cancer are effectively destroyed by the mechanisms available to the immune system. Therefore cancer develops if the immune system is not working properly or the amount of cells produced is too great for the immune system to eliminate.
(Simplified from:www.digital-recordings.com/publ/cancer.html)


6. How to get chocolate

Have we wondered how we get chocolate from? Well this time we will enter the amazing world of chocolate so we can understand exactly we are eating.
Chocolate starts a tree called cacao tree. This tree grows in equatorial regions, especially in place such as South America, Africa, and Indonesia. The cacao tree produces a fruit about the size of a small pine apple. In side the fruits are the tree's seeds. They are also known as coco beans.
Next, the beans are fermented for about a week, dried in the sun. After that they are shipped to the chocolate maker. The chocolate maker starts by roasting the beans to bring out the flavour. Different beans from different places have different qualities and flavour. So they are often shorted and blended to produce a distinctive mix.
The next process is winnowing. The roasted beans are winnowed to remove the meat nib of the cacao bean from its shell. Then the nibs are blended. The blended nibs are ground to make it a liquid. The liquid is called chocolate liquor. It tastes bitter.
All seeds contain some amount of fat and cacao beans are not different. However, cacao beans are half fat, which is why the ground nibs from liquid. It is pure bitter chocolate.

7. The Venus’s fly trap

The United States of America is where the Venus’s fly trap has its origins. The Venus’s fly trap is a unique plant. It belongs to a group of plants called ‘carnivorous plants’. These plants feed on insect. The Venus’s fly trap has a special mechanism by which it traps its prey. This is how it works.
At the end of each leaf – which grows from the base of a long, flowering stalk – there is a trap. The trap is made up of two lobes and is covered with short, reddish hairs which are sensitive. There are teeth like structures around the edge of the lobes.
The trap contains nectar which attracts insect. When an insect comes in contact with the nectar, the trap snaps shut. There are certain digestive juice inside the trap which digest the insect. It takes about ten days for a trapped insect to be digested. We can tell when this digestion is complete, for then the walls automatically open to wait for another victim.
There are two hundred species of carnivorous plants. Another kind of these well- known species is the pitcher plant. What differentiates this plant from the Venus’s fly trap is the shape; the mechanism to catch insects is the same in both plants.
The pitcher plants which cling to other plants by means of tendrils. At one end of the tendril, there is a pitcher –shaped vessel with an open lid. The mouth and the lid of the pitcher contain glands which produce nectar to attract insect. When an insect settles on the nectar, the lid of the pitcher shuts, trapping its victim. The digestive juices inside the pitcher then begin to work

8. The effects of acid soil

Soils with a pH of less than 7.0 are acid. The lower the pH, the more acid the soil. When soil pH falls below 5.5, plant growth is affected. Crop yields decrease, reducing productivity
Soils provide water and nutrients for plant growth and development. Essential plant nutrients include phosphorus, nitrogen, potassium and sulfur. Plants require other elements such as molybdenum, in smaller quantities. Some elements e.g aluminum and manganese, are toxic to plants.
Nutrients become available to plants when they are dissolved in water. Plants are able to take up phosphate, nitrate, potassium and sulfate ions in solution.
The solubility of nitients changes with pH. In acid soils (low pH), molybdenum becomes less soluble and aluminium becomes more soluble. Therefore, plant growth may be affected by either a deficiency of molybdenum or too much aluminum.
Both crop and pasture plants are affected by acid soils. there may be a range of symptoms. Crops and pastures may be poorly established resulting in patchy and uneven growth. Plant leaves may go yellow and die at the tips. The root system of the plant may be stunted. Crops may yield less.
Plants vary in their sensitivity to low pH. Canola and lucerne are very sensitive to acid soils so do not grow well. Lupine and triticale are tolerant to soils of low pH so they still perform well.
Land can become unproductive if acid soil is left untreated. Incorporating lime into the soil raises the pH. Therefore, liming soil can reverse the effects of acid soil on plants and return a paddock to productivity.