Geography Revision. Year 9 and 10

Transcription

1 Geography Revision Year 9 and 10

2 The layers of the Earth

3 Destructive Plate Boundary

4 Constructive Plate Boundary

5 The Kobe Earthquake Richer part of Kobe is located in the south east of Japan, near a destructive plate margin. It is a megacity and has one of the largest container ports in the World. Although further from a plate margin than most of the cities in Japan, Kobe is still found on a fault line. the world At this plate margin, the Pacific plate is being pushed under the Eurasian plate, stresses build up and when they are released the Earth shakes. This is known as an earthquake happening along a subduction zone. The focus was only 16km below the crust and this happened on the 17th Jan 1995 at 5.46am. 10 million people live in this area. The earthquake that hit Kobe during the winter of 1995 measured a massive 7.2 on the Richter scale (or 6.9 on the more current Moment magnitude scale).

6 The Effects The effects of this earthquake were catastrophic for an MEDC. despite some buildings having been made earthquake proof during recent years many of the older buildings simply toppled over or collapsed. A lot of the traditional wooden buildings survived the earthquake but burnt down in fires caused by broken gas and electricity lines. More than 5000 died in the quake 300,000 were made home less More than 102,000 buildings were destroyed in Kobe, especially the older wooden buildings. Estimated cost to rebuild the basics = 100 billion. The worst affected area was the centre. This was because it was built on easily moving ground which LIQUIFIED, allowing building to collapse and sink. The worst effected area was in the central part of Kobe including the main docks and port area. This area is built on soft and easily moved rocks, especially the port itself which is built on reclaimed ground. Here the ground actually liquefied and acted like thick soup, allowing buildings to topple sideways. Emergency aid for the city needed to use damaged roads but many of them were destroyed during the earthquake. Raised motorways collapsed during the shaking. Other roads were affected, limiting rescue attempts. Many small roads were closed by fallen debris from buildings, or cracks and bumps caused by the ground moving. The earthquake occurred in the morning when people were cooking breakfast, causing over 300 fires, which took over 2 days to put out.

7 Haiti Earthquake poorer part of the world Haiti is the poorest country in the Western Hemisphere, its GDP is only $1,200 per person, 207 th in the world, its HDI is incredibly low at 0.404, 145 th in the world, and 80 % of its 9.7 Million people live below the poverty line. Port Au Prince, the capital, is on a fault line running off the Puerto Rico Trench, where the North American Plate is sliding under the plate. The fault line is a strike slip fault, the Caribbean Plate south of the fault line was sliding east and the smaller Gonvave Platelet north of the fault was sliding west. There were many aftershocks after the main event. The earthquake occurred on January 12 th 2010, the epicentre was centred just 10 miles southwest of the capital city, Port au Prince and the quake was shallow only about kilometres below the land's surface. The event measured 7.0 on the Richter Magnitude scale.

8 The Effects 316,000 people died and more than a million people were made homeless, even in 2011 people remained in make shift temporary homes. Large parts of this impoverished nation where damage, most importantly the capital Port Au Prince, where shanty towns and even the presidential palace crumbled to dust. 3 million people in total were affected. Few of the Buildings in were built with earthquakes in mind, contributing to their collapse The government of also estimated that 250,000 residences and 30,000 commercial buildings had collapsed or were severely damaged. The port, other major roads and communications link were damaged beyond repair and needed replacing. The clothing industry, which accounts for two-thirds of 's exports, reported structural damage at manufacturing facilities. It is estimated the 1 in 5 jobs were lost as a result of the quake Rubble from collapsed buildings blocked roads and rail links. The port was destroyed Sea levels in local areas changed, with some parts of the land sinking below the sea The roads were littered with cracks and fault lines

9 Predicting and preparing for earthquakes Prediction involves trying to forecast when an earthquake will happen. Japan tries to monitior earth tremors with a belief that warning can be given, but this did not happen at Kobe. Foreshocks do occur, but on a timescale useful to evcuation. Experts know where earthquakes are likely to happen, but struggle to establish when. Even looking at the time between earthquakesin a particular area does not seem to work. Similarly, experts struggle to pinoint exactly where along a plate margin they will occur. Animal behaviour has been used in the past Protection invloves building to an appropriate standard and using designs to withstand movement. Preparation involves hospitals, emergency services and inhabitants practising for major diasters, including having drills in public buildings and a code of practice so that people know what to do to reduce the impact and increase their chance of survival.

10 Monitoring Volcanoes Monitoring gas emissions As Magma rises into magma chambers gases escape for the depressurising magma. One of the main gases is Sulphur Dioxide, and if its quantity in escaping volcanic gas increases this can signal the start of a major eruptive sequence. In the Mount Pinatubo Volcanic event the amount of Sulphur Dioxide increased by 10 times in 2 weeks. Directly before eruptions the Sulphur Dioxide level can then drop rapidly and scientists think this is due to the sealing of gas passages by hardened magma. This increases pressure in the volcano and leads to explosive eruptions. Ground deformation The movement of magma within the lithosphere can deform the ground above, this has been witnessed at Yellowstone beneath Yellowstone Lake. This swelling of the volcano signals that magma has collected near the surface. Scientists monitoring an active volcano will often measure the tilt of the slope and track changes in the rate of swelling. Mount St Helens showed this prior to its eruption in Thermal monitoring Both magma movement, changes in gas release and hydrothermal activity can lead to thermal emissivity changes at the volcano's surface. We can use satellite imagery, activity of minor extrusive features such as geysers and hot springs and mapping to monitor this. Satellite Images and Remote Sensing Remote sensing is the use of satellites to detect things about the Earth s surface. This is useful for monitoring any changes in volcanoes at the surface. Using satellites we can monitor the thermal activity of the volcano to check for upwelling magma, we can check for escaping Sulphur dioxide using gas sensing and we can look to see if the ground is deforming by checking before and after images of the ground. The satellite can also judge if the ground is being uplifted by measuring the distance between the satellite and the ground.

11 Some other useful signs Some other useful warning signs: Earthquakes are a frequent sign of an impending eruption and their frequency and strength can be recorded Bulging on one side of the volcano - the swelling is obvious and a clear sign of magma moving Tiltmeters can identify small, subtle changes in the landscape Global Positioning Systems (GPS) use satellites to detect movement of as little as 1mm Satellites can detect changes in surface temperature Digital cameras can be used to check for changes in volcanic activity Gases being emitted from the vent change before an eruption Robots called 'spiders' are often deployed to look inside the rim of the volcano The past frequency of eruption is often investigated: the gap between eruptions and the pattern of lava flows, ash movement and lahars can tell people about how the volcano is likely to behave

12 Tropical Storms

13 How do Tropical Storms form? Hurricanes need a lot of heat to form and a sea surface temperature of at least 26 C, which is why they usually occur over tropical seas. They also need to be between 5 and 20 north or south of the equator. It works like this: 1. When this warm and wet air rises, it condenses to form towering clouds, heavy rainfall. It also creates a low pressure zone near the surface of the water. 2. Rising warm air causes the pressure to decrease at higher altitudes. Warm air is under a higher pressure than cold air, so moves towards the space occupied by the colder, lower pressure, air. So the low pressure sucks in air from the warm surroundings, which then also rises. A continuous upflow of warm and wet air continues to create clouds and rain. 3. Air that surrounds the low pressure zone at the centre flows in a spiral at very high speeds - anticlockwise in the northern hemisphere - at speeds of around 120 km/h (75 mph). 4. Air is ejected at the top of the storm which can be 15km high and falls to the outside of the storm, out and over the top, away from the eye of the storm. As this happens, it reduces the mass of air over the eye of the storm - causing the wind speed to increase further. Some ejected air also cools and dries, and sinks through the eye of the storm, adding to the low pressure at the centre. 5. The faster the winds blow, the lower the air pressure in the centre, and so the cycle continues. The hurricane grows stronger and stronger. 6. Seen from above, hurricanes are huge circular bodies of thick cloud around 450 km (300 miles) wide. The cloud brings heavy rain, thunder and lightning. 7. In the centre is the eye of the hurricane, about 45 km across (30 miles) across. Often there will be no clouds in the eye. Seen from below it will seem calmer, with a circle of blue sky above. The eye is formed because this is the only part of the hurricane where cold air is descending. 8. In the northern hemisphere, the prevailing easterly tropical winds tend to steer hurricanes toward land - although their course is unpredictable. As hurricanes move inshore, their power gradually reduces because their energy comes from sucking up moist sea air.

14 Tropical Storms and Climate Change Global warming by the end of the 21st century will likely cause tropical cyclones globally to be more intense on average (by 2 to 11%). This change would imply an even larger percentage increase in the destructive potential per storm, assuming no reduction in storm size. Anthropogenic warming by the end of the 21st century will likely cause tropical cyclones to have substantially higher rainfall rates than present-day ones, with a model-projected increase of about 10-15% for rainfall rates averaged within about 100 km of the storm center.

15 Hurricane Katrina Katrina was a category 4 storm. Storm surges reached over 6 metres in height. New Orleans was one of the worst affected areas because it lies below sea level and is protected by levees. These protect it from the Mississippi River and Lake Ponchartrain. The levee defences were unable to cope with the strength of Katrina, and water flooded into the city. Despite an evacuation order, many of the poorest people remained in the city. People sought refuge in the Superdome stadium. Conditions were unhygienic, and there was a shortage of food and water. Looting was commonplace throughout the city. Tension was high and many felt vulnerable and unsafe. 1 million people were made homeless and about 1,200 people drowned in the floods. Oil facilities were damaged and as a result petrol prices rose in the UK and USA. There was much criticism of the authorities for their handling of the disaster. Although many people were evacuated, it was a slow process and the poorest and most vulnerable were left behind. $50 billion in aid was given by the government. The UK government sent food aid during the early stages of the recovery process. The National Guard was mobilised to restore and maintain law and order in what became a hostile and unsafe living environment.