- Distinguish between:
Latitude and Longitude
- Lines of latitude run from west to east while lines of longitude run from north to south.
- Lines of latitude are parallel to each other while lines of longitude are not parallel to each other but converge at the poles.
- Lines of latitude get shorter towards the poles while lines of longitude are of the same length.
- In the lines of latitude, the equator is the only great circle while in the lines of longitude it has many great circles as any opposite pairs of lines make a great circle.
- Lines are latitude is called parallels while lines of longitude are called meridians.
- Lines of latitude are used for measuring distance while lines of longitude are used for calculating local time.
Greenwich Mean Time and Standard Time
- Greenwich Mean Time (GMT) is the time at the Greenwich Meridian (longitude 0*). It is also called the world time. All countries in the world take or adjust their time from the GMT. Cities on longitude 0* which therefore observe GMT are London (Britain) and Accra (Ghana). For example, if the GMT in London or Accra is 4.00pm, Nigeria local time will be 5.00pm. In other words, Nigeria is one hour ahead of the GMT. On the other hand, standard time is the time generally adopted by a country which is usually taken from the central meridian of that country. The need for standard time is to eliminate differences in local time between one town and the other within the same country. Otherwise, time will have to change from one town to another. For example, Nigeria has accepted to use meridian 15*E which is one hour ahead of Greenwich Mean Time. Egypt (30*E) is two hours ahead of GMT. With this, all towns in Nigeria observe the same time i.e. one hour ahead of GMT.
- Identify and explain any four factors which determine the direction of flow of ocean currents.
- Planetary winds: Wind is one of the most important factors responsible for the movement of surface water in oceans. The trade winds move equatorial waters pole-wards and westwards and warm the eastern coasts of the continents. For example, the North East trade winds move the North Equatorial current to warm the Southern and Eastern coast of Brazil.
- Rotation of the Earth: As a result of the rotation of the earth, ocean waters are deflected to the right in Northern hemisphere and to the left in Southern hemisphere.
- Temperature differences: Ocean waters at the equator are more heated and; therefore, warmer and lighter than those at the poles. Thus, those at the equator flow on the ocean surface towards the poles while those at the poles are cold and heavy; thus, creeping below the bottom of the ocean towards the equator.
- The Shape of the Landmass: Warm and cold currents flow in obedience to the topography and configuration of the landmass. The landmass may divert the currents from the direction initially taken by the current to different directions totally.
- Salinity: Where the salinity of an ocean is high, the ocean water is dense or heavy and it creeps (or moves) at the bottom of the ocean to low salinity areas. Where the salinity is low, the ocean water is light and flows at the ocean surface towards a high salinity area.
- Using specific examples, discuss the effects of ocean currents on the climate of the adjacent coastal areas
- It modifies the climate of an area by either raising or lowering the temperature of the current.
- Cold current contributes to aridity (deserts) on the landmass it affects, e.g. Benguella current of west coast of South Africa causes Namid and Kalahari deserts, the Canaries current of North West Africa causes the Saharan deserts.
- Cold current also causes coastal fogs (instead of actual rain) which are a source of danger as it reduces visibility for airplanes and ships.
- Warm currents bring regular and heavy rainfall to their coastlands e.g. Mozambique current of South East Africa and Guinea currents of West Africa bring rain to their coastlands
- Coastal fogs caused by cold current reduce the temperature of the areas where they occur.
- Warm ocean currents, by warming the winds blowing over them, raise the temperature of the adjacent lands.
- Warm Ocean current helps to keep ports in Polar Regions free from ice.
- Write explanatory notes on the:
Equinoxes: These refer to two particular day of the year when all parts of the world experience equal days and night.
- It is the time when the mid-day sun is directly overhead at the equator.
- It occurs on March 21 and September 23.
- March 21st equinox is also called Spring Equinox while September 23rd is referred to as Autumn Equinox.
- There are 12 hours of daylight and 12 hours of darkness.
- During equinoxes, all places on the earth have equal days and night on these days.
- Refer to any circle that divides the globe into two equal parts.
- The centre of the great circle is also the centre of the earth.
- The equator is the only line of latitude that is a great circle.
- While two opposite lines of longitude make a great circle, e.g. 90*E and 90*W or 180* longitude and 0* longitude.
- The shortest distance between any two points on the earth’s surface lies along the circumference of the great circle which passes these points.
- The great circle route is often used by aircraft on a long distance journey, e.g. Polar air route between London and Los Angeles over Greenland.
- Infinite number of great circles (imaginary lines).
The reasons why the period of twilight is longer along the Arctic than at the Equator are:
- There is half-light in the sky.
- It is caused by a reflection of the sun’s light as it goes down the horizon.
- There is little or no twilight at the equator because the sun rises rapidly and sets rapidly.
- The sun rises almost vertically from the horizon at the equator.
- It occurs longer at higher latitudes because the sun sets more slowly.
- The sun rises and sets at a low angle.
- Distinguish between Deflation and Abrasion
- Deflation involves blowing while abrasion involves hauling rocks against rock surface by wind.
- Deflation involves rolling loose materials along the ground where as in abrasion; rock surfaces are polished, scratched and worn away.
- Deflation usually results in lowering land surface while abrasion is most effective at the base of rocks.
- Deflation is associated with wind while abrasion can be caused by wind, water and wave.
One Landform produced by Deflation and Abrasion
Deflation: One landform produced by deflation is the deflation hollow.
- It is a basin or saucer-shaped feature.
- It could be extensive.
- It is produced by the scooping away of loose sandy materials by wind.
- Sometimes, it is below the water table.
- May therefore form an Oasis or swamp, e.g. Foyum Quattara.
Abrasion: Zeugen is a landform produced by abrasion.
- It is a tabular mass of land with a layer of soft rock beneath a layer of resistant rock.
- It is weird looking ridge-furrow landscape.
- Lying parallel to one another with hard rocks that may overhang.
- Continuous abrasion lowers the Zeugen and widens the furrow.
- Give any two reason why wind erosion is more active in arid than in humid regions
- Absence of vegetation cover encourages free wind action in arid region whereas in humid region vegetation impedes wind speed.
- In arid region the soil is friable and light due to lack of moisture and therefore is prone to wind erosion whereas in humid region moisture helps to bind the soil and thus reducing soil erosion.
- Absence of rainfall encourages soil exposure in arid region whereas rainfall encourages soil protection by vegetation in humid region.