Y9 exam Flashcards
Why do earthquakes occur?
Due to movement of earth’s plates. Friction and pressure cause it.
Where do earthquakes occur?
Found along plate boundaries+major fault lines
Around African plate
Edge of Indo-Australian plate
Linear formation around West coast of America
Clustered in a linear pattern+long narrow belts
Hotspots eg Hawaii
Anomalies- within plates eg Eurasian-China
What is the focus? Are deep or shallow focuses more effective?
The point where earthquakes originate, deep focuses cause less damage and are less felt than shallow.
What is the epicentre?
The point directly above the focus, where the earthquake is most felt.
What are shockwaves?
Seismic waves generated by an earthquake that move through the earth’s crust, travel out from the focus.
Describe the primary waves
The first waves that travel fastest and cause back and forth movement.
Describe secondary waves
They are slower and cause side to side movement
Describe longitudinal waves.
They cause up and down movement
Describe transverse waves.
Cause side to side movement which causes much damage.
What is the Richter scale?
A logarithmic scale that measures the strength or magnitude of an earthquake. The number after is after is 10x more powerful than the one before
What is the Mercalli scale?
A scale that is used with Roman numerals
What is a fault line?
Line along tectonic plates slowly move towards or away from each other
What are seismic waves?
A wave produced by an earthquake (usually) Earthquakes energy is released in seismic waves.
What are the 3Ps that reduce impact of earthquakes?
Prediction- forecast when an earthquake will happen
Preparation- hospitals, emergency services, inhabitants practicing drills
Protection- building to an appropriate standard
Give an example of an MEDC (more economically developed country) country, when it happened, the population and it’s magnitude on the Richter scale.
Kobe- Japanese earthquake, measured 7.2 on Richter scale
Tuesday 17th Jan 5.46am 1995
Kobe- 2nd most populated and industrialised area in Japan.
Population- 1.5million
Where was the focus and epicentre for Kobe’s earthquake?
Focus- 16km below surface (shallow)
Epicentre- Close to a heavily populated area (so loads of damage)
What was the cause of Kobe’s earthquake?
Destructive plate boundary- denser oceanic Philippines plate subducted under less dense Eurasian continental plate
What were the primary and secondary effects of Kobe?
Primary- Ground shook 20s and 3mins on reclaimed land! ground moved 50cm horizontally and 1m vertically, buildings and bridges collapsed
Secondary- 6000 deaths, 30,000 injured, 300,000 homeless, refugees moved to temp. accommodation, collapsed buildings blocked roads (hard for emergency services) fires caused by fractured gas mains+sparks from cables, 7500 wooden houses burnt down
What were the short and long term responses for Kobe?
Short- emergency shelter for 300,000 found in schools, town halls, parks, several days for emergency rations to arrive, rescue teams searched 10 days for survivors
Long- many moved away permanently, jobs created in construction industry (rebuilding programme), railways back in Aug, water, electricity, gas, telephone services back in Jul, most ports working next yr but Tanshin expressway down, new laws to make buildings+transport earthquake proof, more instruments installed to monitor earthquakes.
Example of LEDC earthquake, where, magnitude, date, epicentre
Haiti earthquake- 12th Jan 2010 (Tues) 4:53pm. 7 on Richter scale.
Haiti- Island of Hispaniola in Caribbean Sea
Epicentre 25km south west of capital, Port-au-Prince
Strongest earthquake to hit Haiti in 200yrs
What was the cause of the Haiti earthquake?
Conservative plate boundary with North of Caribbean plate and North American plate
Why did people die in the Haiti earthquake?
Shallow focus
Very densely populated
Poorest country in Western Hemisphere
Buildings not earthquake-resistant
3million in Port au Prince lived in slums
Rescue teams hampered by damage to port, airport+roads
Effects of Haiti earthquake?
Buildings collapsed 316000 deaths 300,000 injured 1.5 million homeless Infrastructure damaged: port, airport, electricity network, roads, water supply Roads blocked with rubble
Responses to Haiti earthquake?
Local used hands to dig people out of rubble
Countries sent aid but airport damaged, delays. When fixed, aid piled up but lack of fuel
Delays caused looting+violence
Rubble blocked roads
Port badly damaged
Refugee camps for the homeless
Oct 2010- cholera killed 5000, blamed Nepal, led to violence
NGO- Oxfam, Red Cross, water aid, action aid, save the children
Hurricane Tomas- Nov 5th 2010, led to flooding and increase in cholera
What are Tsunamis?
Special type of wave (or series of waves) where entire depth of sea or ocean is set in motion by an event (often an earthquake) which displaces water above it and creates a huge wave
How are tsunamis usually caused?
Caused by earthquakes at sea- when plates suddenly move against each other. Energy from the earthquake vertically jolts seabed by several metres, displacing hundreds of cubic km of water
Which way do tsunami waves travel? And what are their movement?
Large waves move through ocean away from epicentre. At deep water, tsunamis move fast but at coastal slowly but increase height. Water pulled back from beach exposing sea bed to create wave
Give an example of a Tsunami, date, magnitude of earthquake that caused, epicentre
Japan Tsunami- 11th March 2011, earthquake- 9 on Richter scale
Epicentre- 100km east of Sendai, out at sea
Cause of Sendai tsunami? Speed of tsunami? Size and number of waves?
Subduction of pacific plate (200km length) under North American plate causing flick upwards of earths crust (5-10m) Speed- 80kph across pacific 40m high after 30m+9 more 10m ones 1000+ aftershocks Swept up to 10km on shore
Responses to Sendai tsunami?
Emergency services weren’t prepared (only for earthquakes)
Specialist search and rescue teams
100,000+ Japanese soldiers distributed essentials
Exclusion zone around Fukushima nuclear plant
Building and reconstruction
Tsunami defences extend beyond 12 m (acceptable level)
Effects of Sendai tsunami
20,000+ deaths 500km2 coastal plains inundated 200,000 buildings destroyed Ruptured gas pipes --> fires Explosions at Fukushima nuclear plant, topped flood defences and contaminated Electricity cut off at 6million homes No running water in 1million homes Heavy snow blocked by debris+landslides and aftershocks hampered relief efforts
Define a volcano
An opening or vent in the earth’s surface where molten material erupts and solidifies as lava
Where are volcanoes found?
On or around plate boundaries In a linear form, long narrow belts esp around Pacific plate (Ring of fire) Along plate boundaries esp constructive and destructive Mid-Atlantic ridge
