Natural Environments Flashcards
What are the different factors which affect climate?
Latitude, distance from sea, prevailing winds, ocean currents, altitude
How does latitude affect the climate?
- Places near the Equator are much warmer than places nearer the poles
- this is due to the curvature of the Earth and the angle of the sun
- at the equator the Sun is always high in the sky
- when it is overhead it shines directly downwards concentrating its heat into a small area which will become very hot
- in contrast the Sun is always low in the sky towards the poles
- this means that its heat is spread over a wider area and so temperatures remain lower
- the lower the angle of the sun the greater the amount of atmosphere through which the rays have to pass.
- This means that more heat will be lost to gases dust and cloud in the atmosphere
- this is why places in the south of Britain can expect to be warmer, especially in summer, than places further north.
How does distance from sea affect the climate?
- The sea (a liquid) is less dense than the land (a solid) and can be heated to a greater depth
- this means that the sea takes much longer to heat up in summer than does the land, but once warmed, however, the sea retains its heat for much longer and cools down more slowly than the land in winter
- this is why places that are inland are warmer in the summer but cooler in winter than places on the coast
- a country surrounded by sea tends to get cold summers and mild winters
How does prevailing winds affect the climate?
- prevailing winds will bring warm weather if they pass over a warm surface (land in summer, the sea in winter) and cold weather if they blow across cold surfaces (the land in winter, the sea in summer)
- as Britain’s prevailing winds blow from the south-west, they are cool in summer but mild in winter
How do ocean currents affect the climate?
- Many coastal areas are affected by ocean currents
- the North Atlantic drift (Gulfstream) is a warm current of water which originates in the Gulf of Mexico. it keeps the west coast of Britain much warmer in the winter than other places in similar attitudes
- IMPORTANT EXAMPLE: The Benguela current causes coastal fog along the coast of the Namib desert in Namibia, however as the foggy air moves inland the water droplets quickly evaporate. daytime warming, as the air passes over the land, reduces its relative humidity and chance of precipitation
How does altitude affect the climate?
- Temperatures decrease on average by 1°C for every 100 m in height
- as many parts of the Scottish highlands are over 1000 m, they will be at least 10°C cooler than coastal places
- in fact, the wind chill factor will make them colder, and enable snow to lie for long periods during the winter
Draw and label a Hadley cell
Include :
- Wet warm air rises -low-pressure
- condensation on the tropopause
- dry air moves towards the poles
- air cools
- dry cold air sinks - clear skies and direct sunlight
- air warms - deserts form
- trade winds push air towards the Equator
- air is heated
What are the different opportunities for human activity in the rainforest?
Farming, Transport, Resources, Settlement
Explain how farming is an opportunity for human activity in the rainforest
Land is cleared for three types of farming:
- ‘Slash and burn’ is the traditional method used by Amerindians in the rainforest. although this is the most sustainable of the three types, it nevertheless causes considerable areas to be cleared, even if only temporarily each year
- Subsistence farming -has increased as a result of the government providing land to some of Brazil’s 25 million landless people. in places, 10 km strips of land were cleared alongside highways and settlers were brought in from places that were even poorer, like the drought areas in the north-east
- Commercial cattle ranching - is run by large transnational companies which sell beef mainly to fast food chains in developed countries. these companies burn the forest, replacing trees with grass
Explain how transport is an opportunity for human activity in the rainforest
- Over 12,000 km of new roads have been built across the rainforest, the largest being the 5300 km trans-Amazonian highway
- these roads were built to develop the region and transport timber, minerals, farm produce and people
- a 900 km railway has been built in carajas to the coast and numerous small airstrips have been constructed
Explain how resources is an opportunity for human activity in the rainforest
The main types of resources are:
- timber- mainly hardwoods are obtained by logging companies which fell trees for markets in developed countries. While timber is a valuable source of income for Brazil, little attempt has been made to replant deforested areas
- Minerals- provide the region with a vast natural resource. they include: iron ore, bauxite, manganese, diamonds, gold and silver
- Hydroelectricity- is an important renewable source of energy but the building of dams and the creation of large lakes has led to large areas of forest being flooded
Explain how settlement is an opportunity for human activity in the rainforest
- The development of Amazonia has led to an increase in population from 2,000,000 to over 30,000,000
- large tracts of forest have been cleared for the development of such new settlements, as Maraba (150,000) and Carajas
What are the different impacts of human activity?
Reduction of species diversity, impact on soils and nutrient cycle, rivers, reduction in number of Ameridians, climatic change
How does human activity have an impact on the reduction of species diversity?
- A typical patch of rainforest 10 km Square could obtain as many as 1500 species of flowering plant, 750 species of tree, 400 types of bird, 150 varieties of butterfly, 100 different reptiles and 60 types of amphibian.
- deforestation has destroyed many of these species, some of which have proved to be of considerable value
- we already get over half of our medicines from the rainforest -one of these recently discovered was the periwinkle -has reduced deaths from child leukaemia from 80 to 20%
How does human activity have an impact on soils and nutrient cycle?
- The clearance of trees means that there is no canopy to protect the soil from heavy afternoon rain or roots to bind it together
- the result is less interception and infiltration and more surface run-off and soil erosion
- deforestation also breaks the nutrient cycle and existing nutrients are rapidly washed out of the soil, leaving it infertile
- this loss infertility has already caused as some of the new subsistence farms and the larger cattle ranches to be abandoned
How does human activity have an impact on rivers?
Many rivers has been polluted due to mining operations
How does human activity have an impact on the reduction of number of Ameridians
- There has been a huge reduction in the number of the Amerindians (from 6 million when the Europeans arrived to the present number of 200,000) and destruction of their traditional culture and way of life
- those remaining such as the Kayapo are forced to live on reservations
How does human activity have an impact on climatic change
- Deforestation is causing climatic change into ways:
- with fewer trees there is less evapotranspiration and therefore less water vapour in the air. with less moisture in the hydrological cycle there is already evidence of reduced rainfall totals together with the threat of a possible increase in local droughts
- at the same time the burning of the forest is accelerating global warming by releasing huge amounts of carbon dioxide ,the main greenhouse gas.
- it is possible that there already changes in the composition of the atmosphere.
- scientists already claim that over one third of the worlds fresh oxygen supply comes from the tropical rainforest- this would be lost of the region was completely deforested
How much precipitation does a desert receive every year
Less than 250mm
How hot are hot deserts
They can have very high daytime temperatures often over 50°C and low nighttime temperatures below 20°C with clear skies.
Describe the global distribution of hot deserts
- Most are located at latitude is from 15° to 30° on the western side of continents (e.g South Africa,Central Australia, mid-east, Sahara)
- however the Mojave, Mexican, Iranian and Thar deserts line north of the Tropic of Cancer, extending 40°N
- Hot deserts are found in subtropical and tropical latitudes
How does lack of cloud cover affect desert climate?
-Desert air has a very low relative humidity, so little clouds form. -this causes extreme to daily (diurnal) temperatures and very large daily temperatures ranges all year round
Why is rainfall so rare in deserts?
-high pressure (explained on handles cell) means convection is seldom strong enough to rise through the descending air
Draw a diagram showing how relief rainfall
Include:
- vegetation on left
- warm, moist air is pushed up mountain
- dew point temperature on mountain causes condensation
- rain clouds form
- dry air passes over mountain
- air descends and warms
- dry conditions known as rain shadow (deserts)
What is an example of a rain shadow?
-The rain shadow effect of the Drakensberg Mountains forms the Namib desert
For a named area of hot desert, you have studied, (Nabib desert) explain why the climate is hot and dry. (7 marks)
- The Namib desert can be found 30 degrees north of the equator in a high pressure belt. This is an area of dry sinking air. As the air is not rising there is no cooling or condensation and this produces cloudless skies.
- The absence of cloud cover means that no rain can fall, the sun’s heating is intense throughout daylight hours and night temperatures fall rapidly.
- Although the prevailing winds blow from the ocean, it has to cross a mountain barrier, this creates a rain shadow effect on the Drakensberg Mountains. Much of the rain falls on the windward side of the mountain so there is little rain on the leeward side. Much of the Namib desert is in the rainshadow.
- The cold Benguela ocean current leads to the formation of fog on the coast of Namibia. These fogs are soon dissipated as they move inland when the temperatures rise and the air can hold more water vapour.
