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Social sciences: geography

Grade 7

Natural hazards

Module 1

The difference between natural disasters and natural hazards

  • Natural hazards are geographical events which occur naturally UNDER (earthquakes and volcanoes), ON (floods) or ABOVE (climatic conditions such as droughts and tropical cyclones) the surface of the earth. Things such as droughts, floods, tropical cyclones, volcanic eruptions and volcanoes regularly happen on a small scale throughout the world. However, if one of these natural hazards leads to – a significant loss of human life and/or – damage to property, and/or – environmental damage,it is called a NATURAL DISASTER.
  • Disasters know no boundaries, and can lead to the loss of thousands of human lives in the areas where they occur.

1. Droughts

1.1 The occurrence and cause of droughts

1.1.1 What are droughts?

A drought is a continuous and lengthy period during which there is no or insufficient precipitation. Thus it is associated with a lack of water, but it does not always lead to a disaster. It is the relationship between the community and their environment that will determine whether a drought will develop into a disaster or not. Isolated droughts rarely occur out of the blue. They usually creep up on a community over several years.

1.1.2 Where do droughts occur?

Study figure 1. It is a world map showing the areas where most droughts occur. You will note that certain countries experience more droughts than others, but that the African continent and India suffer the most from serious droughts.

Figure 1

Activity 1:

To study the dry regions of south africa

[lo 2.1]

Figure 2

a) Make an estimation as to what percentage of South Africa experiences rainfall of less than 500 mm per year.

b) Where in South Africa are droughts most likely to occur? Why?

c) Where in South Africa are droughts least likely to occur? Why?

d) Name ways in which a farmer in the Northern Cape can take precautionary steps against future droughts.

1.1.3 What causes droughts?

Water is essential for life on earth. A drought is the result of a lack of water. Many people think that a drought occurs merely because it doesn’t rain. A decrease in rainfall does indeed cause droughts, but this is not the only cause.

Study table 1, which shows how other factors can lead to the disastrous conditions which are associated with droughts.

Table 1:

Thus changes in climate are indeed implicated in droughts, but poor environmental management has a greater influence on the disastrous impact of a drought.

1.2 The effect (consequences) of droughts on the lives of people and their socio-economic activities

During a period of about 10 years approximately 60 million people worldwide are affected by droughts, and this number continues to increase. In the 1990s, in Africa alone, 35 million people were affected by drought. What will the situation be in the future?

Study the following list of consequences of droughts:

  • no crop rotation
  • failed crops
  • famine: less food is produced
  • loss of lives
  • wells dry up as a result of the lowered water table
  • stock are slaughtered on a large scale: meat prices fall
  • hydro-electric plants may stop operating: electricity prices rise
  • unschooled labourers earn less income: poverty
  • water restrictions are imposed
  • industries suffer due to a lack of water
  • vegetation dies and disappears
  • dust bowls develop on bare soil, and air pollution worsens
  • workers lose their jobs and their income: unemployment causes crime
  • increasing population places more strain on the environment and a vicious circle of disasters develops
  • water levels of rivers and dams fall and some dry up completely: fish die
  • a decrease in the gross national product (GNP) of the country
  • desertification of marginal areas
  • people are forced to migrate out of drought-ridden areas: many are unschooled

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Geography grade 7. OpenStax CNX. Sep 09, 2009 Download for free at http://cnx.org/content/col11021/1.1
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