Flashcards · 5014 · Topic 6

Natural hazards flashcards

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

Study mode needs JavaScript. Every card is listed below, so you can still cover the answers and test yourself.

All 17 cards

For a quick read-through or printing. Cover the right-hand side to test yourself.

Why do explosive volcanoes form at destructive plate boundaries?: One plate is forced beneath another and melts, producing magma that rises to the surface.
Why are there no volcanoes at conservative boundaries?: The plates slide past each other, so no plate is destroyed and no magma is produced. Stress is released as earthquakes.
Magnitude vs intensity of an earthquake: Magnitude: the energy released, measured on the Richter or moment magnitude scale. Intensity: how strongly shaking is felt at a place, measured on the Mercalli scale.
How much larger is the ground motion of a magnitude 7 earthquake than a magnitude 5?: 100 times: each whole step on the scale is a tenfold increase in ground motion, and 10 × 10 = 100.
How can volcanic eruptions be predicted?: By monitoring with seismometers for small earthquakes, gas sensors for changing emissions, and measurements of ground swelling.

What are tropical cyclones called in different regions?: Hurricanes, typhoons or cyclones, depending on the region.
Why do tropical cyclones not form on the equator?: The Earth’s rotation is needed to make the system spin, and its effect is too weak at the equator.
What powers a tropical cyclone?: Warm, moist air rises over the ocean, condenses and releases heat, which drives the storm.
How do mangroves protect coasts from cyclones?: Their dense roots and trees absorb wave energy and reduce the force of storm surges.

Why does urbanisation increase flood risk?: Impermeable surfaces such as concrete and drains send rainwater quickly to rivers, shortening lag time and raising peak discharge.
Give a benefit of flooding: Floods deposit fertile silt on floodplains, improving farmland.
Give one advantage and one disadvantage of building a flood embankment: Advantage: protects the area behind it effectively. Disadvantage: costly, and it can move the flood problem further downstream.
What is floodplain zoning?: A soft engineering approach that restricts building on land most at risk of flooding, keeping it for uses such as farmland or parks.

Define drought: A long period of below-average rainfall that leads to a shortage of water.
How can human activity make drought worse?: Overusing water and poor land management, such as overgrazing and deforestation, increase water shortage and soil damage.
Give two drought management methods suited to a low-income farming community: Rainwater harvesting and drought-resistant crops. Drip irrigation and small storage reservoirs are also suitable.
Why can drought lead to conflict and migration?: Crop failure, livestock deaths and water shortages force people to move or compete for scarce resources.