Flashcards · 0680 · Topic 6

Natural hazards flashcards

17 cards on Topic 6, subtopics 6.1 to 6.4. Pick a subtopic or study them all.

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What happens at destructive, constructive and conservative plate boundaries?: Destructive: one plate is forced beneath another; powerful earthquakes and explosive volcanoes. Constructive: plates move apart and magma rises; smaller earthquakes, gentler eruptions. Conservative: plates slide past; earthquakes, no volcanoes.
Focus vs epicentre: Focus: the point underground where an earthquake starts. Epicentre: the point on the surface directly above the focus.
Primary vs secondary effects of an earthquake: Primary: the immediate effects of shaking, such as collapsed buildings, deaths and broken roads and pipes. Secondary: later effects such as fires, landslides, tsunamis, disease, homelessness and economic loss.
How are earthquake and volcano risks managed?: Earthquakes cannot be reliably predicted, so the focus is preparation: resistant buildings, building codes, drills and land-use planning. Volcanoes can be monitored with seismometers, gas sensors and ground-deformation measurements to give warnings.
Why do people live near volcanoes?: Fertile volcanic soils, geothermal energy, minerals and tourism.

What conditions are needed for a tropical cyclone to form?: Warm ocean water of at least about 26.5 °C, and a position away from the equator so that the Earth’s rotation makes the system spin.
Why do tropical cyclones weaken over land?: They lose their energy supply of warm, moist air from the ocean, which releases heat as it condenses.
What is a storm surge, and why is it so dangerous?: A rise in sea level driven by strong winds and low pressure. It floods low-lying coasts rapidly and often causes the greatest loss of life.
How can the impact of tropical cyclones be reduced?: Tracking by satellite and radar for warnings, evacuation plans, cyclone shelters, strengthened buildings, coastal defences, mangrove protection and education.

What causes river floods?: Prolonged or intense rainfall, rapid snowmelt, saturated or impermeable ground, urbanisation that sends water quickly to rivers, and deforestation.
Hard vs soft engineering flood management: Hard: dams, embankments, flood walls, channel straightening; effective but costly and may move the problem downstream. Soft: floodplain zoning, afforestation, wetland restoration, warning systems; cheaper and more sustainable.
What is lag time on a flood hydrograph?: The time between peak rainfall and peak river discharge. Urban surfaces shorten lag time and raise the peak.
Rain peaks at 09:20 and the river peaks at 13:05. What is the lag time?: 3 hours 45 minutes.

What is a drought?: A long period of below-average rainfall that causes water shortage.
What causes drought?: Persistent high-pressure systems, changes in ocean and atmospheric patterns, and climate change. Overuse of water and poor land management make the effects worse.
What are the impacts of drought?: Crop failure and food shortages, livestock deaths, reduced water supply, wildfires, migration and conflict over resources.
How can drought be managed?: Water conservation, rainwater harvesting, drip irrigation, drought-resistant crops, storage reservoirs, reuse of treated wastewater and early warning from rainfall monitoring.