Chapter 3
ACTIVITYS
Natural Hazards In Australia
3.1 Natural hazards and natural disasters:
1. What is the difference between a natural hazard and a natural
disaster? A hazard is an event or object that is a potential source of harm
to a community. A disaster occurs as the result of a hazardous event that
dramatically affects a community.
2. Explain how a bushfire can be both a natural and human hazard. A
bushfire can be caused by careless humans, we also impact them by
inadequate preparation and poor disaster planning
3.2 Droughts:
1. What is meant by the term ‘drought’? A prolonged period of
abnormally low rainfall, resulting in a shortage of water.
2. What is the difference between drought and low rainfall? A drought
happens when there is not enough water for a community’s needs,
therefore if it was a small town with low rainfall it may not be a drought
where as if it was Sydney with low rainfall its more likely to be a drought.
3. Explain why there is little chance that all of Australia would be
affected by drought at the same time. Rainfall is common in some
places more than others, also some towns are large and require a higher
amount of rainfall then a smaller town.
4. How often might droughts be expected to occur in Australia?
Between 4 and 38 years.
5. What are the two main types of drought that occur in Australia in
terms of duration? Short and intense or long lived
6. Describe the economic impacts of a drought in Australia. The drought
of 1963–68 affected large parts of the continent and was the longest
drought ever in central Australia. The last two years of the drought saw a
40% decrease in the wheat harvest, the loss of 20 million sheep and a
decrease in farm income of around $500 million.
7. Why does Sydney store more water than any other comparable size
city in the world? Because Australia is one of the driest countries in the
world and has to be prepared for common droughts and low rainfall
3.5 Bushfires:
1. What is a bushfire? A fire in the bush, scrub or forest that spreads
rapidly.
2. How have bushfires been an essential input into some Australian
ecosystems? Ash left over from bushfires is rich in potassium, calcium
and magnesium, which help return minerals to the soil, making the
ground more fertile. Also the heat from the fire releases seeds to begin
new growth.
3. What is arson? How could arson be the cause of some of the worst
bushfires? Arson is the deliberate setting of fires and can cause some of
the worst bushfires because stupid people can start it with stronger fuels
over bigger areas.
4. How could very strong, hot winds affect crown fires and make them
very dangerous? Hot winds as well as dry vegetation make bushfires
spread rapidly
3.9 Storms:
1. Explain what is meant by (a) a storm, (b) a thunderstorm and (c) a
severe thunderstorm.
a. A storm: a violent disturbance of the atmosphere with strong winds
and usually rain, thunder, lightning, or snow.
b. A thunderstorm: a storm with thunder and lightning and typically
also rain. Occurs with cumulonimbus clouds.
c. A severe thunderstorm: a thunderstorm featuring one or some of
the following; hail stones, wind gusts, tornados, heavy rain.
3.11 Tropical cyclones:
1. What is a tropical cyclone? A system of winds rotating inward to an area
of low atmospheric pressure, with a counterclockwise (northern
hemisphere) or clockwise (southern hemisphere) circulation
2. Why do tropical cyclones usually die out if they move inland?
Because the warm water vapor from the ocean helps the cyclone form
3.12 Floods:
1. Define a flood and describe the three main types of floods.
An overflowing of a large amount of water beyond its normal confines,
especially over what is normally dry land.
1. Slow-onset floods. These occur along the flood plains of inland rivers
and may last for weeks and even months. They are caused by heavy rain
and run-off upstream, and the water can take days and even weeks to
affect farms and towns downstream.
2.Rapid-onset floods. These occur in mountain headwater areas of larger
inland rivers or rivers flowing to the coast. The rivers are steeper and the
water flows more rapidly. Rapid-onset floods are often more damaging
because there is less time to prepare.
3. Flash floods. These occur due to heavy rainfall of short duration, such
as in a severe thunder- storm. This type of flooding causes the greatest
risk of property damage and loss of life as it can happen so quickly. It can
be a serious problem in urban areas where drainage systems are
inadequate.
3.13 Earthquakes:
1. What are the focus and the epicenter of an earthquake? A focus is the
area underground where the Earth’s crust has snapped, sending shock
waves to the surface. The point on the Earth’s surface above the focus is
called the epicenter.
2. How are earthquakes measured? On a seismograph
3. What does the Richter scale measure? The amount of energy an
earthquake releases
4. How much greater is the magnitude of an earthquake of 8.0 than one
of 7.0? 8.0 is 30 times greater than 7.0
5. Describe the damage caused by earthquakes with the following
measurements on a Modified Mercalli scale:
a. II: not felt by people generally. Just recorded by a seismograph.
b. V: things indoors fall over.
c. VI: houses suffer considerable damage, some collapse.
d. IX–X.: houses collapse everywhere, complete destruction.