Tectonic Hazards Flashcards
All 18 cards in this deck
What drives the movement of tectonic plates?
Convection currents in the mantle, and slab pull where a dense sinking plate drags the rest of the plate with it.
Describe the global distribution of earthquakes and volcanoes.
They occur in long, narrow belts along plate margins, e.g. around the edge of the Pacific Ocean (the Ring of Fire).
At a constructive plate margin, how do the plates move and what hazards result?
Plates move apart; magma rises into the gap, giving gentle volcanic eruptions and weak, shallow earthquakes.
At a conservative plate margin, how do the plates move and what hazards result?
Plates slide past each other (in different directions or at different speeds); friction locks them until pressure is released as an earthquake.
True or false? Earthquakes can happen at all three types of plate margin.
True. Earthquakes occur at constructive, destructive and conservative margins – but volcanoes do not form at conservative margins, because no magma reaches the surface there.
Give two primary effects of the Nepal earthquake (2015).
About 9000 people killed and 20 000 injured; over 3 million left homeless as buildings, roads and historic sites (e.g. Dharahara Tower) collapsed.
Give two secondary effects of the Nepal earthquake (2015).
An avalanche on Mount Everest killed 19 people; landslides blocked roads and valleys, and tourism income fell sharply.
Give two immediate responses to the Nepal earthquake (2015).
International search and rescue teams and helicopters rescued survivors; emergency aid of tents, food, water and medical care was distributed.
Give two long-term responses to the Nepal earthquake (2015).
Roads were cleared and Everest trekking routes reopened to restore tourism; homes and heritage sites were rebuilt using international aid and loans (over US$3 billion pledged).
Give two immediate responses to the Chile earthquake (2010).
Emergency services and the army responded within hours, setting up field hospitals and emergency shelters; power and water were restored to 90% of homes within 10 days.
Why are the effects of an earthquake usually worse, and the responses slower, in a low income country than in a high income country?
Poorer countries have weaker buildings with unenforced building codes and poor infrastructure, and less money for monitoring, emergency services and rebuilding, so they rely on foreign aid.
Give three reasons why people continue to live in areas at risk from tectonic hazards.
Fertile volcanic soils for farming; jobs from tourism, mining or geothermal energy; family, home and work ties, or being too poor to move; belief that eruptions/earthquakes are rare or that protection will keep them safe.
Name two things scientists monitor to help predict a volcanic eruption.
Small earthquakes/tremors (seismometers), ground swelling or bulging (tiltmeters), gas emissions such as sulfur dioxide, and rising ground temperature.
Give two design features of an earthquake-resistant building.
Rubber shock absorbers (base isolators) in the foundations, cross-bracing or a steel frame that can sway, deep foundations into bedrock, and automatic gas shut-off valves.
State two ways that planning can reduce the damaging effects of an earthquake or volcanic eruption.
Plan evacuation routes and practise drills; prepare hazard maps of areas most at risk; stockpile blankets, clean water and food and educate people on what to do.
True or false? Monitoring and prediction can stop a volcanic eruption happening.
False. They cannot prevent the event, but warnings allow evacuation and preparation, which reduces deaths and damage.
Which management strategy is generally most effective at reducing deaths from earthquakes, and why?
Protection through earthquake-resistant building design and enforced building codes, because most deaths are caused by collapsing buildings and earthquakes cannot yet be reliably predicted.
True or false? Earthquakes can be reliably predicted, giving the exact date and place they will strike.
False. Unlike volcanic eruptions, earthquakes cannot be predicted reliably — monitoring only shows which areas are at risk, so protection and planning matter most.