The Moringa tree is relatively unknown in the West, despite the fact that it is incredibly useful. [I] It is a relatively small tree that typically grows to between three and ten metres tall. [II] Its flowers are creamy-coloured and have been compared to small orchids. [III] The plant has long and round green pods that can grow to 30 cms and which took a bit like drumsticks, hence the tree's common name. [IV]
The leaves are reputed to have anti-inflammatory and anti-bacterial properties, so are used for eye and ear infections, fevers, etc. They are also held against the forehead to reduce headaches, or made into tea to treat stomach complaints. As they contain a lot of iron they have been used for the treatment of anaemia, a medical condition in which there are too few red cells in the blood, causing tiredness. The plant also contains many other nutrients, such as phosphorus, calcium, potassium, and vitamins A and C.
The ground-up seeds are commonly used to treat certain skin infections, but can be used for much more. Ground seeds can be mixed with salt or oils to apply to the body to treat cramp, back ache and forms of arthritis, a medical condition in which the joints are swollen and painful. The oil, called Ben oil because it contains behenic acid, is also used as a hair treatment or a perfume, and to deter mosquitoes and treat their bites. The byproducts of the oil manufacturing process are used for fertilization and water purification.
The roots work in exactly the same way as the seeds, but are much stronger, so are not used as often. They have additional uses for heart and circulation problems, whereas the gum is sometimes used to treat asthma. The bark has quite a pleasant taste and is sometimes eaten to encourage digestion.
There is not a part of the tree that is not used. The Moringa tree is probably the most beneficial tree in the world.
(Adapted from Get Ready for IELTS: Reading)

The geology of the Earth's surface is dominated by the particular properties of water. Present on Earth in solid, liquid, and gaseous states, water is exceptionally reactive. It dissolves, transports, and precipitates many chemical compounds and is constantly modifying the face of the Earth.
[I] Evaporated from the oceans, water vapor forms clouds, some of which are transported by wind over the continents. Condensation from the clouds provides the essential agent of continental erosion: rain. [II] Precipitated onto the ground, the water trickles down to form brooks, streams, and rivers, constituting what is called the hydrographic network. [III] This immense polarized network channels the water toward a single receptacle: an ocean. Gravity dominates this entire step in the cycle because water tends to minimize its potential energy by running from high altitudes toward the reference point that is sea level. [IV]
The rate at which a molecule of water passes though the cycle is not random but is a measure of the relative size of the various reservoirs. If we define residence time as the average time for a water molecule to pass through one of the three reservoirs - atmosphere, continent, and ocean - we see that the times are very different. A water molecule stays, on average, eleven days in the atmosphere, one hundred years on a continent and forty thousand years in the ocean. This last figure shows the importance of the ocean as the principal reservoir of the hydrosphere but also the rapidity of water transport on the continents.
A vast chemical separation process takes places during the flow of water over the continents. Soluble ions such as calcium, sodium, potassium, and some magnesium are dissolved and transported. Insoluble ions such as aluminum, iron, and silicon stay where they are and form the thin, fertile skin of soil on which vegetation can grow. Sometimes soils are destroyed and transported mechanically during flooding. The erosion of the continents thus results from two closely linked and interdependent processes, chemical erosion and mechanical erosion. Their respective interactions and efficiency depend on different factors.
(Adapted from TOEFL Reading)

[I] Though called by sweet-sounding names like Firinga or Katrina, tropical cyclones are huge rotating storms 200 to 2,000 kilometers wide with winds that blow at speeds of more than 100 kilometers per hour (kph). Weather professionals know them as tropical cyclones, but they are called hurricanes in the Caribbean Sea, typhoons in the Pacific Ocean, and cyclones in the Indian Ocean. [II] They occur in both the northern and southern hemispheres. [III] Large ones have destroyed cities and killed hundreds of thousands of people. [IV]
Tropical cyclones begin over water that is warmer than 27 degrees Celsius (80 degrees Fahrenheit) slightly north or south of the earth’s equator. Warm, humid air full of water vapor moves upward. The earth’s rotation causes the growing storm to start to rotate around its center (called the eye). At a certain height, the water vapor condenses, changing to liquid and releasing heat. The heat draws more air and water vapor upward, creating a cycle as air and water vapor rise and liquid water falls. If the cycle speeds up until winds reach 118 kilometers per hour, the storm qualifies as a tropical cyclone.
Most deaths in tropical cyclones are caused by storm surge. This is a rise in sea level, sometimes seven meters or more, caused by the storm pushing against the ocean’s surface. Storm surge was to blame for the flooding of New Orleans in 2005. The storm surge of Cyclone Nargis in 2008 in Myanmar pushed seawater nearly four meters deep some 40 kilometers inland, resulting in many deaths.
It has never been easy to forecast a tropical cyclone accurately. The goal is to know when and where the next tropical cyclone will form. “And we can’t really do that yet,” says David Nolan, a weather researcher from the University of Miami. The direction and strength of tropical cyclones are also difficult to predict, even with computer assistance. In fact, long-term forecasts are poor; small differences in the combination of weather factors lead to very different storms. More accurate forecasting could help people decide to evacuate when a storm is on the way.
(Adapted from “Reading Explorer 2” by Paul Maclntyre )