Volcanoes, earthquakes and floodsThe Earth comprises of a crust – a hard outer layer like the skin of an apple, a mantle – a layer of very hot and dense rock that flows and moves and a core – the hot centre of Earth that is believed to be made entirely from metal.

A hard layer called the crust covers the Earth. This layer is the outermost layer of rock that covers the Earth and is like the skin of an apple. The crust is thinner in some places than in others. Mountains are areas where the crust is thick. This crust is not one large solid piece; it consists of many smaller pieces that are called ‘tectonic plates’ which are thousands of kilometres in size. These tectonic plates float on the underlying layer of magma and exert pressure as they move.

The mantle comprises of layers of hot slow-moving magma, which causes the tectonic plates to move. This movement causes earthquakes and volcanic eruptions.

The core is the hottest layer of the Earth, comprising of an outer and inner core. Scientists believe that the outer core is made up of nickel and iron, whilst the inner core is largely iron. The outer core is more liquid than that of the inner core. The temperatures within the core range from 5000 – 7000 degrees Celsius. The pressure for the rest of the Earth causes the inner core to be mostly solid, even though the temperature of the core is hot enough to melt the iron.

http://www.nhm.ac.uk/nature-online/Earth/plate-tectonics/index.html

http://science.nationalgeographic.com/science/Earth/the-dynamic-Earth/plate-tectonics-article/

The internal structure of the Earth

Activity 1a) Name the three main layers of the Earth. (1)b) Describe a tectonic plate. (2)c) How does magma contribute to earthquakes? (1)d) Describe the structure of the core. (5)

Total: (9)

http://science.howstuffworks.com/nature/29595-100-greatest-discoveries-plate-tectonics-video.htm

http://science.howstuffworks.com/nature/29595-100-greatest-discoveries-plate-tectonics-video.htm

The crust is not one large solid piece of rock. It consists of many smaller pieces that are called ‘tectonic plates’ which are thousands of kilometres in size. These tectonic plates float on the underlying layer of magma and exert pressure as they move. The edges of the tectonic plates are called ‘plate boundaries’. The tectonic plates move on the layer of hot slow-moving magma that lies underneath the crust. When the plates move, they push and pull against each other causing pressure or sudden shifts.

There are seven large plates and many smaller plates that move very slowly each year. The plates that lie beneath the continents are called continental plates and the plates that lie beneath the oceans are called oceanic plates.

The Tectonic platesThe edges of the tectonic plates are called ‘plate boundaries’. New crust is formed and old crust is returned to the core at these boundaries. The process of the Earth’s crust being formed and returned to the core can take about 100 million years.

Oceanic plates

The structure of the Earth

How the crust moves

These plates meet in different ways:Convergent boundaries:These occur when two tectonic plates push against each other and one plate is forced upwards. This movement causes the formation of mountains or volcanoes. The other plate sinks back into the core and melts. Earthquakes can occur along this type of boundary.

Divergent boundaries:These occur when the tectonic plates pull away from each other. The crust breaks apart. The space that remains is called a rift. Magma seeps up to fill the rift and so new crust is made.

Transform boundaries:This type of boundary is where two plates meet and move against each other horizontally, in different directions. As they move, neither plate is displaced up or down. This movement causes a build up of energy, which may be released in a sudden movement which can cause an earthquake.

Locations around the worldA volcano allows molten rock form the mantle to flow out on to the Earth’s surface through the Earths crust, in the form of lava. Currently, there are approximately 1500 active volcanoes around the world. A small portion of these volcanoes are located beneath the oceans.

http://science.howstuffworks.com/nature/231-how-volcanoes-work-video.htmhttp://www.nhm.ac.uk/nature-online/Earth/volcanoes-earthquakes/volcano/volcano-types/index.htm

Diagram of the African plate, showing the East African Rift zone.

Lakes of the Great Rift Valley as seen from space.

Activity 2a) Define a plate boundary. (1)b) How do the tectonic plates move? (1)c) Name and describe three areas where tectonic plates meet. (6)d) List the names of three tectonic plates. (3)e) Describe the difference between continental and oceanic tectonic plates. (2) f ) Explain why the Great Rift Valley in Africa is a good example of divergent convergence. (3)

Total: 16

Volcanoes

http://video.nationalgeographic.com/video/news/west-mata-submarine-volcano-vin?source=searchvideo

info file:There are 1500 activevolcanoes world wide

A volcano erupting beneath the ocean

Volcanoes are often found near the edges of the tectonic plates that cover the surface of the Earth. The image below illustrates the occurrence of volcanoes around the world and the position of the tectonic plates.

The Ring of Fire is a ring of volcanoes that is found in Pacific Ocean. There are approximately 450 volcanoes in this area. There are frequent earthquakes and volcanic eruptions in this area.

Why volcanoes occurThe pressure caused by the movement of magma beneath the Earth’s crust can force magma up through faults in the Earth’s surface. This movement of magma causes a volcano. When the magma reaches the Earth’s surface, it is called lava. As the lava pours onto the surface, the lava emits poisonous gases. The heat of the lava causes clouds of steam in the atmosphere. The force of the pressure of a volcano can cause rocks, ash and volcanic dust to be blasted into the air. http://video.nationalgeographic.com/video/volcano-lava

Volcanoes can erupt through the same fault or vent over a long period of time. A crater forms at the top of the volcano. After each eruption, lava coats the edge of the crater and builds a cone as the lava cools.

A famous volcanic eruption was that of Mount St Helens in the United States of America. The eruption occurred on 18 May 1980. The eruption destroyed approximately 250 homes and killed 57 people. The eruption removed almost 400m of the volcano leaving a horseshoe shaped crater in the volcano.http://www.discovery.com/video-topics/other/other-topics-volcano-videos.htm

A volcanic eruption

Diagram of a volcano

From top left clockwise, Mount St Helens before, during and after eruption.

Earthquakes occur when part of the Earth’s crust moves. The area where the crust moves is called the ‘fault’ or ‘fault plane’. Large earthquakes occur when the movement is about one to two metres. A small earthquake occurs when the crust moves in millimetres.

The Earth’s outer surface is broken up into what geologists call ‘plates’. Earthquakes occur when the plates move under, over or slide past each other. Most earthquakes occur on the edges of these plates that make up the Earth’s crust. The location below the Earth’s surface where the earthquake starts is called the ‘hypo centre’, and the location directly above it on the surface of the Earth is called the ‘epicentre’.

An earthquake is a sudden, rapid shaking of the Earth caused by the release of energy stored in rocks. This energy can be built up and stored for many years and then released in seconds or minutes. Many earthquakes are so small that humans cannot feel them. Some have caused great destruction and killed many of people.

Sometimes an earthquake has ‘foreshocks’.  These are smaller earthquakes that happen in the same place as the larger earthquake that follows. The largest, main earthquake is called the ‘mainshock’. Mainshocks always have aftershocks that follow.  These are smaller earthquakes that occur afterwards in the same place as the mainshock. 

There are two major regions of earthquake activity on the planet. One region is called the circum-Pacific belt and is also known as the Pacific Ring of Fire, which encircles the Pacific Ocean. The other region is called the Alpide belt, which extends from Java to Sumatra through the Himalayas, the Mediterranean, and out into the Atlantic.

The Ring of Fire is a zone where earthquakes happen frequently. As much as 90% of the

world’s earthquakes and 81% of the world’s largest earthquakes occur along the Ring of Fire. The December 2004 earthquake just off the coast of Sumatra which caused a devastating tsunami, was in the Alpide belt. This belt has 17% of the world’s largest earthquakes.

Instruments called seismographs record earthquakes. The recording they make is called a seismogram. The seismograph has a base that sets firmly in the ground and a heavy weight that hangs free.  When an earthquake causes the ground to shake, the base of the seismograph shakes too, but the hanging weight does not. Instead the spring or string that it is hanging from, absorbs the movement.  The difference in position between the shaking part of the seismograph and the motionless part is what is recorded.

http://science.howstuffworks.com/nature/236-how-earthquakes-work-video.htm

http://video.nationalgeographic.com/video/101-videos/earthquake-101?source=relatedvideo

http://www.nhm.ac.uk/nature-online/earth/volcanoes-earthquakes/earthquakes/index.html

A seismographThe size of an earthquake depends on the size of the fault and the amount of slip on the fault. A seismogram recording made on seismographs will determine how large the earthquake was. 

A short wavy/undulating line that doesn’t move very much means the earthquake was a small earthquake. A long wavy line that moves a lot means a large earthquake. The length of the wave depends on the size of the fault, and the size of the wave depends on the amount of slip. A Richter scale

Activity 3a) Where do volcanoes occur? (3)b) Describe a volcano. (3)c) Explain the difference between magma and lava. (1)d) Why do volcanoes occur? (2)e) Describe the Ring of Fire. (2)e) Briefly describe the eruption of Mount St Helens. (4)

Total: 15

Earthquakes

measures the enormity of an earthquake based on the semiography fluctuations.An example of a seismogram

Earthquakes measuring six and above are considered major quakes. Earthquakes measuring seven and above cause great damage and kill many people.

Other famous earthquakes:

22 May 1960, Chile: quake measuring 9.5 on the Richter scale – struck Santiago and Concepción, triggering tidal waves and volcanic eruptions. 5000 killed, 2000 000 homeless.

28 March 1964, Alaska: quake followed by tsunami – claimed 125 lives, caused millions in property loss. Measuring 9.2 on the Richter scale, it was felt over a large area of Alaska and in parts of Yukon Territory and British Columbia.

http://www.dallasnews.com/sharedcontent/dws

China Mourns Quake DeadMONDAY, MAY 19, 2008 Aljazeer

With the toll from the quake standing at more than 32,000, China’s leaders have declared three days of national mourning for the dead. Many more are still listed as missing and officials say the final toll could rise above 50,000.As the mourning period began on Monday, state media reported that more than 200 recovery workers had been buried by landslides over the past two days in the disaster zone.The official Xinhua news agency gave no details of where the incidents happened, but the report highlights the continued danger faced by relief teams racing against time to find survivors.On Sunday, at least three people were killed in a 6.0-magnitude aftershock.The aftershocks and heavy rain have put recovery crews on heightened alert, fearful further strong tremors could bring down already weakened buildings.But while recovery efforts are switching to focus on clearing up the tonnes of debris, a few survivors are still being pulled out alive from collapsed buildings.The authorities, meanwhile, are also battling to prevent the outbreak of disease, with the risks heightened by the rotting carcasses of 12.5 million livestock and poultry. “Combating epidemics is the most urgent and the biggest task facing us right now,” Wei Chaoan, the vice-minister of agriculture, said on Saturday.The World Health Organisation said that the lack of safe drinking water or proper waste disposal along with cramped conditions in temporary shelters was “conducive” to outbreaks. “Preventing communicable disease outbreaks is the key public health issue now facing the People’s Republic of China,” the UN body said in a statement.

Activity 4Read the articles that follow and answer the questions in your class workbooks.

Earthquake Rocks China!An earthquake of 7.8 magnitude hit China’s Sichuan province on Monday, May 12, 2008. Within one week of the massive quake, at least 32,000 people were reported dead and more than 200,000 injured. Hundreds of aftershocks rippled through the region after the quake, causing landslides and other damage. Unlike hurricanes, no one can predict when an earthquake will hit. There is no warning and no evacuation time. The U.S. Geological Survey (US

GS) says that at least one earthquake happens somewhere on the globe every day, usually small and in remote regions where few people live. But when big earthquakes hit in heavily populated areas, it can easily become a catastrophe.

info file:No one can predict when an earthquake will occur.

info file:Aftershocks and diseasekill many survivors after an earthquake

a) In which country and on which continent is Sichuan located? (2)

b) The world map below shows the earthquakes that took place within a week dated 26 May 2008. Indicate the location of Sichuan on the map. (1)

c) What was the size of this earthquake? (1)

d) There were many aftershocks reported after the earthquake. What further damage did these aftershocks cause? (1)

e) Can earthquakes be predicted? (1)

f ) Why is it more catastrophic when an earthquake hits a densely populated area, than when an earthquake hits a less populated area? (2)

g) Provide the abbreviation for the World Health Organisation. (1)

h) What role did the WHO play in the aftermath of the Earthquake in Sichuan? (1)

A flood causes a great amount of damage. Heavy rain causes rivers and dams to flood, damaging homes and other buildings, removes bridges and roads, devastates food crops and kills livestock. Floods can be devastating to the local population that live in areas of the flood.

Unusually heavy rains generally cause floods when the natural watercourses fail to contain the amount of water accumulated. Floods are also caused by other natural phenomena such as tropical cyclones and tsunamis.

http://www.nhm.ac.uk/nature-online/earth/volcanoes-earthquakes/floods/

http://video.nationalgeographic.com/video/101-videos/floods

Tropical cyclonesTropical cyclones are also known as ‘typhoons’ and ‘hurricanes’. A cyclone is a storm system characterised by a low-pressure centre and powerful thunderstorms that produce strong winds and flooding rain. A tropical cyclone feeds on heat released when moist air rises, resulting in condensation of water vapour contained in the moist air.

Cyclones circulate counter clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.

Cyclones, hurricanes and typhoons can be predicted several days in advance. These disasters are usually more destructive than floods.

Possible damage by cyclones:High winds cause major damage to infrastructure and housing. They are generally followed by heavy rains and floods and by tidal waves in flat coastal areas.

Floods

A cross section of a cyclone

info file:Fortunately, cyclones can be predicted in advance.

Storm surges develop over large bodies of warm water, and lose their strength if they move over land. This is the reason coastal regions can receive significant damage from a tropical cyclone, while inland regions are relatively safe from receiving strong winds.

Storm surges can produce massive coastal flooding (up to 40 kilometres from the coastline) and heavy rainfall can produce inland flooding

Accurate landfall predictions of a cyclone can give only a few hours’ notice to threatened populations. People generally opt to wait until the very last minute before abandoning their home and possessions. Deaths from drowning in the high tides and sudden flooding and material losses are therefore often very high.

Information adapted from: http://www.ifrc.org/what/disasters/about/types/hydrometeorologic/hurricanes.asp

How are hurricanes/cyclones named?All hurricanes are given names to help us identify storms and track them as they move across the ocean. There can be more than one hurricane at a time and without naming them, we could get confused about which storm we’re talking about.

An Australian meteorologist began giving women’s names to tropical storms before the end of the 19th century. In 1953, the US National Weather Service, began using female names for storms. By 1979, both women and men’s names were used. One name for each letter of the alphabet is selected, except for Q, U and Z.

These are the hurricane names used in 2007:Andrea, Barry, Chantal, Dean, Erin, Felix, Gabrielle, Humberto, Ingrid, Jerry, Karen, Lorenzo, Melissa, Noel, Olga, Pablo, Rebekah, Sebastien, Tanya, Van, Wendy

The World Meteorological Organization uses six lists in rotation to name hurricanes. The same lists are reused every six years. The only time a new name is added is if a hurricane is very deadly or costly. Then the name is retired and a new name is chosen.

Some of the retired names are: Katrina, Andrew, Rita and Wilma

Cyclone NargisOn 2 May 2008 tropical cyclone Nargis hit the coast of Myanmar and devastated large parts of the low-lying Irrawaddy delta. Winds exceeding 190 kilometres per hour ripped through the Myanmar’s biggest city Yangon for more than ten hours. Homes were flattened, structures damaged, trees uprooted and power lines collapsed. In rural parts of the country up to 95 per cent of homes were demolished.

info file: The World Meteorological Organiationuses lists to name hurricanes.

Hurricane classificationHurricanes are classified into five categories based on their current maximum wind speed. This rating scale is called the Saffir-Simpson Hurricane Scale, named after Herb Saffir and Robert Simpson, who developed it. Category 1 -- Winds 119 – 153 km/h Minimal damageCategory 2 -- Winds 154 – 177 km/h Moderate damageCategory 3 -- Winds 178 – 209 km/h Extensive damageCategory 4 -- Winds 210 – 249 km/h Extreme damageCategory 5 -- Winds over 249 km/h Catastrophic damage (these are very rare) There are very few Category 5 storms; most storms that achieve Category 5 status only hit Category 5 status for a very short time, then the winds subside to a less powerful level. Some of the strongest recent hurricanes (Atlantic Ocean tropical cyclones) that hit Category 5 status include: Hurricane Felix (September 2007) -- Caribbean Hurricane Dean (August 2007) -- Gulf of Mexico, Yucatan Peninsula, Mexico, Caribbean Hurricane Wilma (October 2005) -- Gulf of Mexico, Yucatan Peninsula, Mexico, Cuba, and Southern Florida Hurricane Rita (September 2005) -- hit Texas, Louisiana Hurricane Katrina (August 2005) -- hit southern Louisiana, Mississippi and Alabama Hurricane Isabel (September 2003) -- hit North Carolina, Maryland, Delaware, Virginia, and Washington, D.C. Hurricane Mitch (October 1998) -- hit Honduras, Nicaragua, El Salvador, and Guatemala Hurricane Andrew (August 1992)-- hit south-eastern Florida and south-eastern Louisiana

Japan’s most powerful earthquake since records began has struck the northeast coast, triggering a massive tsunami. The quake was the fifth largest in the world since 1900.

http://science.howstuffworks.com/nature/230-how-tsunamis-work-video.htm

http://www.nhm.ac.uk/nature-online/Earth/volcanoes-earthquakes/tsunami/how-to-spot-a-tsunami/index.html

On March 11 2011, measuring at 8.9 by the US Geological Survey, the tsunami struck at 05:46 GMT at a depth of about 24km.

A 10m-wave struck Sendai, burying farmland and sweeping cars across the airport’s runway. Fires broke out in the centre of the city. Cars, ships and buildings were swept away by a wall of water after the 8.9 magnitude tremor, which struck about 400km (250 miles) northeast of Tokyo. Japan’s NHK television showed a massive surge of debris-filled water reaching far inland, consuming houses, cars and ships. Motorists could be seen trying to speed away from the wall of water.

The tsunami rolled across the Pacific Ocean at 800km/h before hitting Hawaii and the US West Coast, but there were no reports of major damage from those regions.

Activity 5Look at the pictures below. These pictures tell the devastating story of cyclone Nargis that hit Myanmar on 2 May 2008. List the ways in which the people of Myanmar were affected by the cyclone. (9)

Tsunamis

Thousands of people evacuated coastal areas in the states of California, Oregon and Washington. The biggest waves of more than 2m were recorded near California’s Crescent City.

A tsunami warning extended across the Pacific to North and South America, where many other coastal regions were evacuated, but the alert was later lifted in most parts, including the Philippines, Australia and China.

The terrifying wall of water that smashed into northeast Japan was unstoppable. It wasn’t the Earthquake but the following tsunami that caused most devastation in Japan. The tsunami was triggered by an 8.9-magnitude earthquake. This earthquake took place around 400 kilometres from Tokyo, off the coastal city of Sendai.

The tremor itself was a result of the Pacific tectonic plate submerging beneath the North American and Eurasian tectonic plate. The tectonic plate, could not withstand the pressure of submerging. When it cracked, the upper part of the Pacific plate rebounded, causing the sea level to rise by up to 4 meters along a 100 to 150 kilometre fracture zone. This resulted in a wave that travelled at high speed through the ocean towards the shore.

http ://w w w.nhm.ac.uk/nature - onl ine/Ear th/volcanoes-earthquakes/tsunami/how-an-earthquake-causes-a-tsunami/index.html The tsunami reached a wave height of approximately 10 meters. It is not only the height of the wave that is so dangerous, it is the wavelength of 200 meters that unfolds the deadly impact as a huge volume of water filled with debris, cars, ships and even parts of houses crashes onto shore. The chances of surviving this are highly unlikely.

Preparing and responding to floods

The damaging effects of a flood are worsened by the destruction of the natural environment. Dunes, wetlands and barrier islands can protect the land against the effects of a coastal storm. Forests and floodplains natural absorb floodwaters. Deforestation, alien vegetation, land degradation and the diversion of rivers are factors that can contribute the damaging effect of floods.

The wave from a tsunami crashes over a street in Miyako City, Iwate

Deforestation Land degredation

Activity 6Answer the following questions:1) True or False a) The Earthquake caused the most damage in Japan. b) A tsunami was triggered by the Earthquake. c) The epicentre of the Earthquake took place at sea. d) The Earthquake occurred on the Pacific tectonic plate. (4)

2) Why was the chance of surviving the Japanese tsunami wave highly unlikely? (2)3) Look at the picture - a) How do you know that this tsunami wave was powerful and forceful? (2)b) What type of debris can be seen in the tsunami wave? (2)

Total: 10

info file: Tsunami’s are triggeredby an earthquake

Reducing the impact

Activity 7In a paragraph, explain what can be done to resolve each of the factors that contribution to the damaging effects of a flood. (4)