Friday, February 25, 2011

Map Making

A map is a schematic representation of an area. Maps are primarily used to help locate places or plan a journey, and can range from a plan of a farm to a map of the world. Maps may also be used to illustrate information about a particular area; for example, distribution of population, resources or climate. These specialized maps are known as thematic maps.

                In any map the way reality is represented depends on the amount of information it contains, the used of diagrams and other graphic devices, and the scale- the size of the map in relation to the area it shows. The oldest surviving maps were made by the Babylonians more than 4000 years ago. Many ancient mapmakers assumed that the Earth was flat, but the circumnavigation of the globe in the 15th century led to great improvements in the accuracy of map making.  

                Maps show a range of information by the use of symbols and approximations. The first stage of map making is to construct a network of fixed points, from which everything else can be located. That way subsequent error will not accumulate and cause major distortions.  Before map makers had aerial photographs and satellite images to help them, the fixed points were plotted by a process called triangulation. Triangulation points are set up on landmarks such as hilltops. From the angles between these points, distance can be calculated without the need to take measurements on the ground. Adding vertical angle measurements give the heights. The height information on maps is normally shown as contours- lines linking points of the same elevation. It was by setting up a triangulation system across India from the coast to the Himalayas that cartographers first established the Mount Everest was the highest mountain in the world.  Today, satellite images provide the framework and maps are stored on computer so that they can be updated quickly without the need for redrawing.   

Wednesday, February 23, 2011

Stop Climate Change


            The Earth’s atmosphere is now changing more quickly than at any time in the past. In the last 150 years there had been a 25 percent increase in carbon dioxide and a 100 percent increase in methane in the atmosphere, largely as a result of the burning of fossil fuels, the expansion of agriculture and rapid deforestation.

Over the same period, the world‘s climate changed by an average of 0.05 degree Centigrade, as green house gases trap the Sun’s heat within the atmosphere. Computer models predict a continued warming of 0.5 degree a decade unless steps are taken to limit emissions. The climate change would be greater were it not for pollutants such as sulphur dioxide which scatter sunlight back into space. Other gases- notably CFCs from fridges, aerosols and fire extinguishers- are damaging the tenuous layer of ozone in the stratosphere which screens out ultra violet radiation from the Sun. 

Steps have been taken to phase out CFCs. They are also powerful greenhouse gases, but legislation to reduce other green house gases will be harder to implement since the practices that produce them are central to modern life. Many nations have pledged to reduce emissions to their 1990 levels, but stronger measures will be needed for stop climate change.

Monday, February 21, 2011

Causes of Climate change

Humans have farmed for thousands of years but in just the last few decades burgeoning populations have called for more agricultural ingenuity than ever before and subsequently agriculture becomes one of the causes of climate change. The breeding of new crop varieties, the use of fertilizers and pesticides and the bringing of more and more land under cultivation have kept production ahead of population growth throughout most of history which are the main causes of Climate change.. Since 1985, however, the limit seems to have been reached and per capita grain production has started to fall.
                In 1987 world grain reserves were sufficient for 100 days; by 1989 there were only enough for 54 days, yet there are 100 million more people to feed every year. There have been hidden costs to the increases in productivity. It is thought that about 40000 people in the developing world die of pesticide poisoning every year and the pesticides also one of the environment hazards.  Twenty four billion tones of top soil are lost from crop lands each year, eroded by wind and water.
                Irrigation is lowering the water table beneath eight states in the Great Plains of the USA by a meter a year, and the diversion of rivers for irrigation in the former Soviet has reduced the Aral Sea to about a third of the size it was 25 years ago. One tenth of the Earth’s land surface is currently given over to agriculture but there will have to be yet further changes before food production is sustainable.

Tuesday, February 15, 2011

Human Impact on Earth: urbanization

           As the world’s population expands past the six billion mark, it becomes more and more unevenly distributed. The great concentrations do not always occur on the most productive land; and people tend to gravitate towards what are often already large cities. In 1950 the largest metropolitan areas were all in the developed metropolitan areas were all in the developed world – New York, London, Tokyo and Paris. Now those have been over taken dramatically by Mexico City and Sao Paulo, with Shanghai, Calcutta, Bombay and Jakarta rising rapidly on the list.

                The developing world’s urban population is now larger than the total population of Europe, North America and Japan combined. Many of the cities have grown beyond the control of planners and include illegal slums that pack millions of people together and concentrate populations and disease. An estimated 600 million people in the cities of the developing world lack clean water, sanitation and secure homes. Even if living standards improve, cities seem set to expand, putting more land under concrete and producing more fumes from industry and vehicles in congested streets.

Monday, February 14, 2011

Human Impact: Riches from the Earth

              The Earth is minded for building materials, metals, chemicals and fuels. Powerful machinery, industrial processing and international trade mean that individual deposits are exploited on a scale far beyond local needs. An estimated 23 billion tones of non fuel minerals are extracted each year, about twice the amount of sediment carried each year by the world’s river systems. As a result, an estimated half a million hectares of land are scarred each year. As the most concentrated ore deposits become exhausted, lower grade ores are used, such that to produce an estimated nice million tons of copper in 1990, 990 million tons of ore had to be mined. The open cast Bingham Canyon copper mine in Utah, USA, 775m deep, is the largest human excavation in the world.

      The legacy of mining is not only the hole in the ground and the pile of spoil left behind; it can affect air and water over great distances. The Ilo smelter in Peru emits 600000 tons of Sulphur compounds each year, and cyanide in the waste affects marine life in a 20,000 hectares area. Small scale gold mining by hundreds of thousands of miners in the Amazon basin releases a estimated 100 tones of mercury into the river system each year.

Saturday, February 12, 2011

Human Impact – Interactive processes

             Mining and industry can release toxic metals and other wastes into ground water, and they release metals into the atmosphere as fine particles. They produce acidic gases, such as sulphur dioxide and nitrogen oxides and green house gases, notably carbon dioxide. Human activities, using fossil fuels, notably power generation and transport, are the biggest net emitters of green house gases since they extract the carbon from no renewable sources.
                 Farming practices result in the release of nitrates and phosphates from fertilizers and animal waste into ground water and rivers, adding to sewage already released into rivers and seas and causing blooms of algae which subsequently deplete the oxygen in water.  Although crops absorb carbon dioxide as they grow, they do not store it to the extent that a forest does, and rice cultivation and cattle rising produce another green house gas, methane. Clearance of natural vegetation releases carbon dioxide into the air and soil minerals into water and increases the likelihood of soil erosion.
                Natural systems absorb some, but not all, of the excesses of human activity. Alkaline soils can neutralize acidic gases washed out of the air; forests, grasslands and plankton can absorb carbon dioxide; some waste decomposes and some nutrients are recycled. But few human activities are sustainable in the long term.

Tuesday, February 8, 2011

Human Impact on Earth

              Human have inhabited the Earth for only a fraction of its history, yet they have changed the face of the planet. Their impact is obvious to the eye, even from the space: city lights and gas flares by night sprawling urban areas and the unnaturally straight lines of intensive agriculture by day. With other sensors, vast tracts of pollution are obvious on land, in water and in the atmosphere.
             Mapped over just a few decades, the destruction of forests, the spread of deserts, the reduction in stratospheric ozone and the increase in green house gases are dramatic. All are the result of human activity. In the past, the Earth has displayed a remarkable resilience, globally if not locally; today , an exploding population that demands ever increasing affluence may be pushing the limits of the Earth’s resources and its ability to process waste materials.

             At almost every stage the complex natural cycles between land, sea and atmosphere can be influences, augmented or upset by human activity. Most emissions follow the hydrological cycle. They can wash into ground water and rivers, dissolve in water vapor in clouds and fall again to Earth in rain.

Friday, February 4, 2011

Hurricanes, typhoons, cyclones and tornadoes

  Over very warm areas of ocean, warm, moist air starts rising so fast that it creates a region of intense low pressure beneath it, pulling warmer, moist air in from the sides. The phenomenon can develop into a vast spiraling weather system – a hurricane. Once formed, hurricanes can continue for many days. They tend to drift in the direction of the prevailing trade winds until they strike land. But then, the spiraling winds can reach speeds of 300Km/h, and the whole weather system may be 800Km across. In the middle known as the eye the air can be clear and deceptively still. But the other side of the storm is not far behind.


              Huge cumulonimbus clouds release torrential rain and the winds whip up high waves on the surface of the ocean beneath the hurricane.  The intense low pressure can temporarily raise sea levels by as much as 8m in what is known as a storm surge, which can cause serious flooding. Once hurricane is traveling over land, its supply of moist air is cut off and the storm eventually subsides.

       Storms that arise in the North Atlantic and batter the Caribbean and southeastern USA are called hurricanes. Those in the Pacific that threaten Southeast Asia are typhoons, and those in the Indian Ocean that have caused such extensive flooding and damage in the Indian subcontinent are cyclones.

                Tornadoes are also caused by rapidly rising spirals of air but they are on a much smaller scale than hurricanes, pulling air up into a thundercloud. Though affection a smaller area, they can be just as devastating as hurricanes, tearing off roofs and sucking up almost anything in their path, resulting in some surprising objects raining down later.