Tropical Cyclones Heta and Katrina
Focus Statements. • natural and cultural characteristics (features) of the environments that make them vulnerable to the extreme natural event(s) • natural processes that operate to produce the extreme natural event(s) • effects of the extreme natural event(s) on the natural environments • effects of the extreme natural event(s) on the cultural environments • how different groups of people have responded to the effects of the extreme natural event(s).
Weather Map reading and air pressure (n) • Air pressure always moves from high to low pressure. • When an area has low pressure in the middle and close isobars it shows that it is extremely windy. • When an area has high pressure and the isobars are far apart it means that it is probably warm and still. • Low pressure systems have rising air that is being heated therefore it is light. • High pressure systems have sinking air that is cooling therefore is more dense.
Weather • processes\Weather maps presentation.pptx
Tropical Cyclones!!! • Tropical Cyclones are areas of extreme low pressure. • This low pressure creates violent storms that are characterised by winds over 100km/h and heavy rainfall. • They have caused the loss of life on a number of occasions due to there intensity. • In parts of Australia they are called Willy Willies, Asia they are called Typhoons, Northern Hemisphere they are called Hurricanes. • So lets look at what creates them.
Climatic Processes • Heating of the sun at the equator causes air to rise creating an area of extreme low pressure near the earths surface. • The air that is heated by the sun rises into the upper atmosphere, where it cools and condenses (becomes heavier), descends at latitudes 25 degrees n+s. (Remember sinking air is low pressure) • As high pressure always moves towards low winds are created. These are known as the trade winds. • These winds converge 5 degrees North and south in a area known as the ITCZ.
The Trade winds: Where the trade winds meet rainstorms occur (frontal rainfall) They meet at the Inter Tropical Convergence Zone (ITCZ)
How a TC forms • 5 Step diagram • Copy in Processes above and on earth diagram pg 109. • Summarise into 3 step diagram (exam)
Tropical Cyclones • TC’s in the Southern Hemisphere move in a south-easterly due to the trade winds and the spinning effect of the tropical cyclone. • Once the cyclone has reached the eye there is a period of calm followed by winds in the opposite direction these repeat the process of the earlier winds. • When a cyclone cannot produce enough latent heat to feed itself or it reaches a large land mass it looses strength and becomes a depression again. • Questions: Pg 108. • processes\CYCLONE PROCESSES cloze.docx
Physical Changes • How do tropical cyclones affect the land? • Violent waves • Storm Surges • Storm Waves • Heavy rainfall. • Read pages 114,118 answers questions.
Physical Changes • Brainstorm what are the earth altering affects of cyclones? Brainstorm how these conditions alter the land. (Think if somehow a cyclone formed over Dunedin. • I.e. wind can break off branches. • Notes • natural environment\Tropical Cyclones effect on natural environment brief notes.doc
High Islands • Tropical cyclones affect high Islands in a different way to low Islands. High Islands are usually volcanic mountainous Islands like those of Hawaii. Due to their altitude they are more prone to the effects of wind, and erosion often in the form of landslides.
Low Island • Low Islands are also called coral atolls and they literally are very low to the ocean. Some don’t get more than 5 metres above sea level. These islands are more prone to flooding, either from rain, storm surges or high seas.
Drawing the islands • Draw each island and the effects it feels from page 112. Each island should be drawn ½ page in size.
Cultural Environment • Tropical Cyclones affect the social environment in a large number of ways. • These affects are either economic or Social. • Economic is referring to how the affect the flow of money in the area they strike. • Social is how the affect the way people move and interact in their daily life. • The affects of Tropical Cyclones are usually Negative i.e. loss of life however there are also times when they have benefits for people.
Activity • Using the template write the following effects of TC’s into the top boxes. • High seas, storm surges, heavy rain, Strong winds. • In the second row of boxes explain what problems these things could create. • In the 3rd column explain how these problems could affect the economy. Do it Neatly!!!!!!
Activity • Using these words create another diagram: • High seas, Storm surge, heavy rain, strong winds. • Explain what these conditions lead to.’ • Explain how these affect people’s day to day living.
Preparing for before, during and after a TC. • For the people who live in areas where cyclones form (Pacific Islands) TC’s are inevitable. • People in these areas have made and are making adjustments to their lives so TC’s don’t affect them as much in the future. • These adjustments can occur either before during or after the TC has struck.
Before during and after. • Groups of 3-4 diagram: How could we prepare for a tropical cyclone. • Create notes using pages 120-123 put each paragraph into your own words. This is also homework. • Do activities page 123.
NIUE • Title Niue and Tropical Cyclone Heta! • Read through Pasifika book answer the following question including Question within Answer: • What kind of Island is Niue? • How high are the cliffs around the ocean? • What height does Niue dip to in the middle? • Why would this potentially be hazardous for cyclones? • What is the rock that makes up the Island of Niue?
Cyclone Heta • Cyclone Heta was a powerful category 5 cyclone that caused massive damages to Tonga, Niue, and American Samoa in late December 2003. • Heta ended up causing 207 million dollars worth of damage to the pacific Islands it came in contact with.
Heta: (Formation) • Ocean in the pacific was heated to 27 degrees C. • Heta formed January 1 2004 over a deserted part of pacific ocean just south of Tokelau. This is the cyclone season due to suns position. • Heta formed at 10 degrees south of the equator where trade winds are strong. • Heta air pressure = 915hpa • Winds of over 250 km/h
Heta Hits Niue • Cyclone Heta travelled south east towards the small atoll of Niue which would feel the full force. • Using pages 111-113 construct a timeline of the events for Cyclone Heta.
Heta hits the natural environment (n) • Niue is a small coral atoll of only 250 square km located 19 degrees south of the equator. • Niue’s highest point if only 68 metres above sea level. • These factors combined with the 7 metre storm surge and the 10 metre waves and 300km/h gusts of wind meant the damage that was done to Niue and its capital Alofi was extensive.
The damage • Mass flooding • Buildings and buildings roofs being ripped clean off. • Coral Deposition from reefs 200m below sea level • Salinisation of fresh water supply • Eroding of banks in the north • Mass vegetation stripping from wind and.. • Vegetation being stripped from salt spray.
Heta affects the natural landscape • Small coral atoll of only 256 square km. • Heta flooded Niue with 4-7m storm surges and 10 metre waves that washed 100m inland • Coral was removed from the reef and deposited onto the beach front by the storm surge. • Storm surge eroded the beach front and created steep banks. It also demolished substantial amounts of vegetation on its way. • Coral reef was removed from 200m below sea level. • Salt water contaminated fresh water.
Continued • Wind gusts up to 300 km/h caused severe damage • 80% of the trees had their foliage ripped off. • Coconut trees were uprooted. • Some of the foliage that remained was killed by the salt spray that was whipped up by the wind and killed vegetation • The huge period of drought after the cyclone provided the island with a large fire risk
Social effects of Cyclone Heta • One life lost. • Hundreds of homes destroyed. • 200 residents made homeless – 10% of population. • The hospital was basically destroyed. • Fresh water supplies contaminated with salt water • Sewage pumps no longer worked. • No running water available. • People traumatised and needing counselling.