Geography

Geography Statistics- this is the representation of information on figures obtained from various resources. Dot maps –a dot distribution map is used to represent population density. This is the average number of persons per square km. Choropleth maps- these represent average values over a given area. The information is shown on this map by a system of shading or coloring. Pyramidal graphs-this shows the population of a country according to age and sex groups.

Flow map-this shows the measurement and volume of passengers cargo and shipping. Maps- this is like a computer in that it gives a wealth of information on a particular area or country. There are many different type of maps. Topographical map-this gives information on the physical layout of features of the country. The elements on a map: title this consists of the name, sheet and edition. Scale- is an indication of the size of the map and is given in either meters or kilometers.

Compass direction- this indicates north, true north and magnetic north. Key or legend- this contains conventional signs and symbols Border or frame- this ensures that the map is neat. Types of maps: geographical maps – tells us about the nature and distribution of rocks and rock types. Weather map- tells us about weather conditions. Climatic map- tells about the climate of an area. Political map- shows us where political boundaries are located.

Economic map- shows the distribution of economic activities e.g. agriculture. Grid reference-there is two major type o grid references; six and four figure grid references. Grid lines are referred to as Eastings and Northings. Easting lines are vertical and run from north to south on a map. Northing lines are horizontal lines running from east to west on a map. To find the location of a place on a map read the easting line then the northing.

A compass is an instrument which is used to measure directions. Compass or angular bearings give the precise direction of any particular point from another and are expressed in degrees. Contour lines are lines joining places at same height above sea level. Gradient –this determines the particular rise of the land over a given distance. Gradient= vertical interval/ horizontal distance. Or: gradient= difference in vertical height/ distance apart.

Method: difference in height=m-m Distance based on scale= km to m Gradient = m/m= Cross sections A cross-section of a map gives a profile representation of what a section of a country or feature or area looks like. Plate tectonics Plate tectonics refers to the crustal movements of plates on the earth’s surface the earth’s surface is made up of a series of plates or slabs. A tectonic plate is therefore a rigid shell of the earths crust. They carry and support the

continents and form seafloor. The movement behavior of these plates is referred as plate tectonics. This concept was developed in the 1960’s to explain the earth’s structural components. The earth’s crust or lithosphere is divided into 9 major plates and several minor one’s which 100-200km thick .The continents make up continental plates while the seafloor is made of oceanic plates. Plates are constantly forming and separating. The plate margins or boundaries are either diverging or

converging. Plates are formed at constructive margins where ridges are formed and consumed at destructive margins due to the subduction of materials. Plate margins are characterized by the presence of volcanic mountains and earthquake activities. Continental drift This refers to the relative movements of continental masses over the surface of the earth. The earth’s surface has undergone horizontal movements. Continents were joined together to form a single continent of a large landmass known as Pangea

during the pre-cambian era about 600-3.5 million years ago. This large landmass was surrounded by a large ocean known as panthalassa which was urlain by a dense material called sima whuich was made of silicon and magnesium. Beneath the continent was a light material known as sial which was made of silicon and aluminum. Continents were separated forming a southern landmass known as Gondwanaland and a northern landmass known as Laurasia. Gondwanaland consisted of Africa, Madagascar, India, South America, Antarctica and

Australia while Laurasia consisted of Europe, Asia and North America. These continents have drifted apart so that they now maintain their present positions with oceans between them.