| What are natural hazards? | Natural events that threaten people or has the potential to damage infrastructure or the environment. |
| What are tectonic hazards? | Features and processes that relate to the Earth's lithosphere and geosphere. |
| What is the asthenosphere? | The top layer of the mantle. It's pratically solid and liquid and acts as a lubricating layer. |
| What is the crust? | The thinnest layer of the Earth, made up of igneous rock. Its divided into slabs known as tectonic plates and is 40km deep. |
| What are the two types of plates? | Oceanic and Continental. |
| What are the features of the oceanic plate? | It is thin, but dense due to the constant pressure of the water squeezing it together. It is also young and an example of the rock type is basalt. It's always sub-ducted under. |
| What are the features of the continental plate? | It is thick and less dense, but older. It has many air pockets and an example of the rock type is granite. |
| What are the features of the inner core? | It is solid and made up of iron and nickel. It is also the hottest part of the earth, reaching 6,000°C. |
| What are the features of the outer core? | It is liquid and made up of iron and nickel. It's around the same temperature of the inner core. |
| What are the features of the mantle? | It is made up of semi-molten rock and is the thickest layer, around 2.900km. It's temperatures at its boundary with the core is 3,700°C, and its boundary with the crust is 1,000°C.
The upper section of the mantle is called the asthenosphere which is made up of magma. |
| What is magma? | Semi-molten rock. |
| What are the features of the crust? | It is 0-60km thick and is the outer layer of the Earth. It's solid rock and the temperatures range from 200-400°C. |
| What is a plate boundary? | The boundary where two plates meet. |
| How do convection currents work? | Heat from the core ruses and heats the rock in the mantle, making it rise.
Semi-molten rock spreads out and carries the tectonic plates.
Soon after, it cools and sinks to be reheated.
It's the movement of tectonic plates due to heat and energy. |
| What are the different plate boundaries? | Divergent (constructive), Convergent (destructive) and Conservative. |
| What and where are divergent (contrastive) plate boundaries? | These are margins where two plates move away from each other. This causes magma to rise from the mantle to fill in the space, which later cools and forms new crusts.
It creates shield volcanoes and small earthquakes, an example is the mid-atlantic plate/ ridge. |
| What and where are convergent (destructive) plate boundaries? | These are margins where two plates move towards each other. The oceanic plate meets the continental plate and is forced down into the mantle, and destroyed. The sub-ducted plate melts and rises abruptly as magma.
They form destructive earthquakes, volcanoes and tsunamis, an example is the Nazca plate being sub-ducted beneath the less dense South American plate. |
| What and where are conservative plate boundries? | These are margins where two plates are moving sideways against each other, or in the same direction but at different speeds. The crust isn't created or destroyed.
This creates destructive earthquakes and an example is the San Andreas fault. |
| Explain why earthquakes and volcanoes occur at plate boundaries (6 marks) | Earthquakes occur at conservative plate boundaries due to the friction when they move past each other. Theses create tremors and cracks in the ground and buildings. An example of an earthquake is the San Andreas fault as the conservative boundary.
Volcanoes occur at convergent plate boundaries where the oceanic plate is forced under the continental plate and into the mantle. The magma rises to fill in the gap when the sub-ducted plate melts. An example is the Nazca plate being sub-ducted under the South American plate. |
| What are plumes? | Concentrated zones of heat that move towards the surface, bringing magma. |
| What are hotspots? | Columns of heat in the Earths mantle, found in the middle of tectonic plates. |
| What is the Mauna Loa? | The largest active volcano that erupted for the first time in 1984. The lava is 1000°C and it means 'long mountain'. |
| What is released from volcanic eruptions? | Lava, pyroclastic flow, ash, dust, gases and steam is released. |
| Where are volcanoes generally found?
Name where they are concentrated and anomalies. | They are generally found at plate boundaries, but concentrated along conservative boundaries like the Pacific ring of fire, and some divergent plate boundaries like Iceland.
Some anomalies is the hotspot volcano in Hawaii - the Mauna Loa. |
| What are the 3 states of volcanoes? | Active volcanoes, dormant volcanoes and extinct volcanoes. |
| What are active volcanoes? | Volcanoes that are erupting or have activity like temperature changes or the releasing of gases. |
| What are dormant volcanoes? | Volcanoes that were one active but are now due to erupt. They have potential to become extinct. |
| What are extinct volcanoes? | Volcanoes that will no longer erupt. |
| What are the 3 main volcaones? | Composite volcanoes, shield volcanoes and hotspot volcanoes. |
| What and where are composite volcanoes? | Steep-sided and tall volcanoes that build in height after every eruption. They are found on convergent boundaries and have andesitic lava. |
| What and where are sheild volcanoes? | Low, gently-sloping domes that look like a warrior's shield. The basaltic lava can erupt from several places including fissures. They're found on divergent boundaries. |
| What and where are hotspot volcanoes? | Volcanoes that form due to plumes in the mantle. The magma rises in cracks or weak areas in the crust, and are found on the plate itself. |
| What are fissures? | Cracks in the ground. |
| Describe the formation of convergent volcanoes. | Cracks or weaknesses in the convergent plate boundaries allow magma to come up. Pressure from the gases from the oceanic crust when it was subducted, pushes magma from the mantle into the crust.
Gases build up to make a volcano erupt. After several eruptions when the lava cools and solidifies, it creates a mountain or cone-like shape, forming a composite volcano. It releases andesitic lava which has a high silica content, meaning ts more viscous, so the lava won't travel far. |
| What is andesitic lava? | Magma that is thick because it has a high silica content, making it viscous. |
| What is basaltic lava? | Magma that has a low silica content, meaning it's less viscous. |
| What does viscous mean? | The lava's resistance to flow. |
| How are shield volcanoes formed? | When magma rises to fill in the space where the divergent plate has moved from, the volcano is formed. It also has basaltic lava, so it flows far before cooling, which is which is doesn't really build in height. |
| What is an example of a sheild volcano? | The Laki Fissure in Iceland. |
| Explain which volcanoes are the most dangerous in your opinion. | I think that composite volcanoes are the most dangerous. Although the eruptions are infrequent, when they happen they are very life threatening. Although hotspot volcanoes have the potential to erupt, composite volcanoes are more dangerous since they also have lava bombs and mudflows that can kill people. Shield volcanoes most destroy crops. |
| What is an earthquake? | Intense vibrations within the earths crust that makes the ground shake. |
| What is the focus? | The point in the crust where the earthquake originates. The epicentre is the point on the ground directly above the crust. |
| Where is the most deadly earthquake found? | On the conservative plate boundary in Haiti. |
| What is the Tohoku Japan case study of 2011? | On the 11th of March, 2011, at 2;47 PM, an earthquake with a magnitude of 90 mW shook north-east Japan, triggering a tsunami in the Pacific region.
The Pacific plate which moves 83 mm a year was thrust under the Eurasian plate at the Japan Trench.
Faulting occurred 300 km along the trench causing an upward fault at 10 meters, and a sideways at 50 meters.
The focus was around 30 km below the seabed and the epicentre was 130 km east of Sendai.
Primary impacts were 667-1,479 deaths directly due to the earthquake, no electricity and land subslides.
Secondary impacts were economic costs, high radiation levels and liquefaction. |
| What plates were involved in the Tohoku earthquake in Japan? | The pacfic plate, the Pjilippine plate and the Eurasian plate. |
| What were some preparations Japan made for the Tohoku earthquake? | Billions on shatter resistant glass and shock absorbent buildings, networks of seismographs and tsunami + earthquake drills. |
| What are some enviormental reasons for living near volcanoes? | There's fertile soil around Mount Agung.
There are hot-springs. |
| What are some economical reasons for living near volcanoes? | Some people cannot afford to live anywhere else but in cheap, hazardous areas
Some people are already employed and finding a new job may be hard.
Magma heats the ground making renewable energy (steam) without fossil fuels, creating jobs.
People can get jobs from tourism, e.g 1000 people visit Mount Etna every year.
Metals like diamonds can be found and sold.
Natural sulphur can be found.
They are confident that the government will support them financially. |
| What are some social reasons for living near volcanoes? | 1000s of farmers in Bali are attracted to the fertile soil.
There are hot springs.
They are confident that the government will support them.
Moving away means leaving family and friends.
People believe that it won't erupt, e.g 1 million people live at the foot of Mount Etna, Italy. |
| Why do people live near Iceland's volcanoes? | People live near the volcano in Iceland because;
They have naturally hot water without using gas;
The volcano provides shelter from winds;
Geothermal energy can be used for tourism and electricity;
Hot-water pools attract tourists. |
| Do you think that people in developing countries have a choice on where they live? | Those in developing countries may have less of a choice due to their family as a whole being financially unstable. This may mean that they have to stay with their family in their homes, or if they have a low paying job, they may not have enough money to move out or may be scared of loosing their position in their job since it may be bad enough. This would limit peoples options because they may lose something they cannot gain again, so it wouldn't be worth taking the risk. |
| What is monitoring? | Using scientific equipment to detect warning signs to monitor. |
| What is prediction? | A combination of historical data, monitoring and scientific information to make predictions. |
| What is protection? | The construction of buildings that can provide protection. |
| What is planning? | Emergency plans for areas that are the most vulnerable. |
| What monitoring is done for volcanoes? | Warning signs are shown before eruptions. Gases and hydrology is measured and changes in gravity and volcanic shape is measured. |
| What predictions are done for volcanoes? | Scientific monitoring shows when eruptions may happen. In 2010 there was an increase in earthquake activity under the. Eyjafjallajö-kull ice cap, leading to the eruption later in March/ April. |
| What protection is used against volcanoes? | Earth embankment can be used to divert lava flow from properties like in Italy, Mount Etna. |
| What planning can be done for volcanoes? | Hazard maps show areas that are likely to be affected, showing certain land uses and which areas need to be evacuated. |
| What monitoring is done for earthquakes? | Usually they occur without warning, but there are some water pressure changes and ground tremors. |
| What predictions are done for earthquakes? | Most predictions for earthquakes aren't accurate, but plate margins at great risks are identified to have earthquakes soon like Istanbul, Turkey. |
| What protection is used against earthquakes? | Buildings and bridges are built to resist the shaking and tsunami walls can protect people, buildings and stations. In Chile, buildings have reinforcement columns and are strengthened with steel. |
| What planning can be done for earthquakes? | Maps are made to show the effects of earthquakes and areas at risk. It also shows which areas need more protection than others. |
