Earthquakes & Volcanoes (Cambridge (CIE) IGCSE Environmental Management): Flashcards
Exam code: 0680
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- FrontEarth Structure
Define crust.
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Define crust.
The crust is the thin, outermost layer of the Earth, made of solid rock.
Which type of crust is thinner and denser?
Oceanic crust is thinner and denser than continental crust.
The mantle is the layer of the Earth, reaching a depth of about 2900 km.
The mantle is the thickest layer of the Earth, reaching a depth of about 2900 km.
What state is the rock in the upper mantle?
The upper mantle is mostly semi-molten rock, while the lower mantle is solid.
True or False?
The inner core is liquid iron and nickel.
False.
The inner core is solid iron and nickel because of the immense pressure; the outer core is the liquid layer.
What drives tectonic plate movement?
Convection currents in the mantle, powered by heat from the core, drive tectonic plate movement.
True or False?
Tectonic plates move several metres each year.
False.
Tectonic plates move slowly, only millimetres to centimetres per year.
Define plate boundary.
A plate boundary (or plate margin) is the place where two tectonic plates meet.
What proportion of earthquakes occur at or near plate boundaries?
About 95% of earthquakes occur at or close to a plate boundary.
What causes an earthquake where plates interact?
Stress builds up where plates collide, separate or slide past each other, and its sudden release causes an earthquake.
Define Pacific Ring of Fire.
The Pacific Ring of Fire is a tectonically active region surrounding the Pacific Ocean that contains about 75% of the world's volcanoes.
How many continents are there?
There are seven continents: Africa, Antarctica, Asia, Europe, North America, Oceania and South America.
Define hotspot.
A hotspot is an area where plumes of very hot mantle rise towards the Earth's surface.
True or False?
Volcanoes only form at plate boundaries.
False.
Hotspot volcanoes form far from plate boundaries, usually in the middle of a tectonic plate.
As a tectonic plate moves over a hotspot, a of volcanoes forms, for example Hawaii.
As a tectonic plate moves over a hotspot, a chain of volcanoes forms, for example Hawaii.
What type of lava do hotspot volcanoes produce?
Hotspot volcanoes produce runny, basaltic lava, which builds broad shield volcanoes.
What happens at the Mid-Atlantic Ridge?
At the Mid-Atlantic Ridge, plates move apart at a divergent boundary and new oceanic crust forms.
What generates the heat in the Earth's core?
Radioactive decay generates the heat (geothermal energy) in the Earth's core.
What does heat rising from the core create in the mantle?
Heat rising from the core creates convection currents in the mantle.
The tectonic plates that make up the crust move on top of the mantle below.
The tectonic plates that make up the crust move on top of the semi-molten mantle below.
Define slab pull theory.
Slab pull theory is the current theory that plate movement needs more than convection currents: the heavier, denser edge of an oceanic plate sinks as it subducts and pulls the rest of the plate along behind it.
True or False?
Conservative plate boundaries produce volcanoes.
False.
Conservative boundaries have no magma generation, so they produce no volcanoes.
Define divergent boundary.
A divergent (constructive) boundary is where plates move apart and rising magma fills the gap, creating new crust.
Divergent boundaries produce earthquakes.
Divergent boundaries produce shallow earthquakes.
Which landforms form at a divergent boundary?
Mid-ocean ridges and volcanoes with gentle lava eruptions form at a divergent boundary.
Define convergent boundary.
A convergent (destructive) boundary is where plates move towards each other and one plate subducts beneath the other.
How does magma form at a convergent boundary?
The subducting plate melts, forming magma that rises to create a volcanic arc.
True or False?
The Andes formed at a divergent boundary.
False.
The Andes formed at a convergent boundary, where the Nazca Plate subducts beneath the South American Plate.
What do convergent boundaries produce?
Convergent boundaries produce powerful earthquakes, explosive volcanoes and ocean trenches.
Define conservative boundary.
A conservative (transform) boundary is where plates slide past one another horizontally, so no crust is created or destroyed.
Why do conservative boundaries produce sudden, violent earthquakes?
Friction locks the plates together until the built-up stress releases suddenly as an earthquake.
At which type of boundary is the San Andreas Fault?
The San Andreas Fault in California lies at a conservative (transform) boundary.
Define focus.
The focus is the point inside the Earth where an earthquake starts.
Define epicentre.
The epicentre is the point on the Earth's surface directly above the focus.
True or False?
The strongest earthquake shaking usually occurs far from the epicentre.
False.
The epicentre usually experiences the strongest shaking.
How does an earthquake release its stored energy?
An earthquake releases stored elastic energy as seismic waves, which cause the shaking.
What does the Moment Magnitude Scale measure?
The Moment Magnitude Scale measures the energy released by an earthquake.
The Moment Magnitude Scale is , so each whole-number increase means about 32 times more energy.
The Moment Magnitude Scale is logarithmic, so each whole-number increase means about 32 times more energy.
What does the Mercalli Scale measure?
The Mercalli Scale measures the damage that an earthquake causes.
Why does magma rise towards the surface?
Magma rises through cracks because of buoyancy and gas pressure.
Define pyroclastic flow.
A pyroclastic flow is a fast-moving cloud of hot gas, ash and rock fragments that can exceed 400°C.
True or False?
Carbon dioxide is the most common volcanic gas.
False.
Water vapour is the most common volcanic gas.
How does volcanic acid rain form?
Volcanic acid rain forms when sulfur dioxide (SO₂) reacts with water in the atmosphere.
Define volcanic bomb.
A volcanic bomb is a large, molten or semi-molten rock ejected during an explosive eruption.
True or False?
Volcanic ash only affects the area close to the volcano.
False.
Ash can travel globally in the upper atmosphere.
Which scale measures the magnitude of a volcanic eruption?
The Volcanic Explosivity Index (VEI) measures the magnitude of a volcanic eruption.
Why can volcanic carbon dioxide kill people?
Carbon dioxide can collect in low-lying areas and cause suffocation.
Why are volcanic soils fertile?
Volcanic materials weather into soils rich in minerals, such as potassium, phosphorus, magnesium and iron.
In geothermal power, steam extracted through wells drives that generate electricity.
In geothermal power, steam extracted through wells drives turbines that generate electricity.
True or False?
Geothermal energy from volcanic regions is a non-renewable energy source.
False.
Geothermal energy is a renewable energy source that reduces reliance on fossil fuels.
Which building materials do volcanoes provide?
Volcanoes provide basalt, pumice and scoria for building and construction.
How do volcanoes make minerals easier to mine?
Hot volcanic fluids deposit minerals in cracks and fissures, bringing them close to the surface.
How does volcanic tourism benefit an area?
Volcanic tourism creates jobs for guides, hotels and restaurants and boosts local and national economies.
Define primary hazard.
A primary hazard is a direct result of an earthquake or volcanic eruption.
Define secondary hazard.
A secondary hazard occurs as a result of the primary effects of an earthquake or eruption.
Which factors affect the impacts of a tectonic event?
Impacts depend on magnitude, distance from the epicentre or volcano, population density, building quality and preparedness.
Define lahar.
A lahar is a mudflow that forms when volcanic ash mixes with water.
Why do airlines cancel flights near a volcanic ash cloud?
Flying through ash clouds can cause jet engine failure.
Poor in evacuation shelters increases the risk of water-related disease after a tectonic event.
Poor sanitation in evacuation shelters increases the risk of water-related disease after a tectonic event.
How do earthquakes cause fires?
Earthquakes cause fires when ruptured gas lines ignite.
What are the three phases of managing a tectonic hazard?
The three phases are before the event (preparation), during the event (survival and protection) and after the event (recovery and rebuilding).
Which instrument records ground movement during an earthquake?
A seismometer records ground movement during an earthquake.
Earthquake warning systems detect the initial and send alerts seconds before the shaking arrives.
Earthquake warning systems detect the initial P-waves and send alerts seconds before the shaking arrives.
True or False?
Scientists can predict the exact time of an earthquake.
False.
Scientists cannot predict earthquakes accurately; warning systems give only seconds of warning.
How do scientists measure ground deformation at a volcano?
Scientists measure ground deformation with GPS and tiltmeters.
Define land use zoning.
Land use zoning is when planning authorities restrict development in high-risk zones.
Why is land use zoning difficult to enforce?
Zoning is difficult to enforce where land is scarce, people build illegally and existing settlements cannot easily move.
How does base isolation protect a building in an earthquake?
Base isolation uses rubber bearings to reduce the transfer of ground movement into the building.
Cross-bracing prevents earthquake-resistant buildings from or buckling.
Cross-bracing prevents earthquake-resistant buildings from twisting or buckling.
Why do buildings in volcanic areas have steep roofs?
Steep roofs prevent ash from accumulating, so the roof does not collapse.
True or False?
All countries can adopt earthquake-resistant building designs equally easily.
False.
These designs cost a lot to build, so high-income countries (HICs) adopt them far more easily.
Which volcanic hazard overwhelms all building designs?
Pyroclastic flows overwhelm all building structures.
What does disaster preparation aim to do?
Disaster preparation aims to reduce panic and improve survival.
True or False?
Evacuation drills stay effective however rarely people practise them.
False.
Drills may be ineffective if they happen too infrequently.
Why might people refuse to evacuate before a tectonic event?
People may refuse to evacuate because they do not want to leave their livelihoods behind.
How do emergency shelters reduce disease outbreaks?
Shelters provide food, water, sanitation and medical care for displaced people.
What is a limitation of emergency shelters?
Shelters can become overcrowded or under-supplied, and long-term sheltering harms mental and physical health.
True or False?
Relying on international aid always speeds up local recovery.
False.
Reliance on aid can slow local recovery, and aid may also arrive too late.
Which stage of tectonic hazard management usually costs the most?
Rebuilding is usually the stage that costs the most, and it can take years.
Rebuilding after a tectonic event offers a chance to improve .
Rebuilding after a tectonic event offers a chance to improve building standards.
Which forms of international aid help after a tectonic disaster?
International aid includes emergency supplies, rescue and medical teams, long-term financial support for rebuilding and technical expertise for monitoring.
What can stop international aid from reaching people?
Political tensions or corruption can hinder the distribution of aid.
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