YEAR 9 Natural Hazards Flashcards
List the four parts of the earth:
The crust, mantle, outer core and inner core
Describe the crust
35-70km thick, like the skin on an apple. The crust is split up into many parts known as the tectonic plates.
Describe the mantle
Has the consistency of jam, contains molten rock, hot, has a high pressure.
Describe the outer core
Largely liquid, made from iron.
Describe the inner core
Solid, made of iron. Radioactive decay takes place here, which ends up causing convection currents.
What is a plate?
A piece of the earth’s crust, there are 7 main ones and other smaller ones.
What is a plate boundary?
Where two plates meet, and they can move in three different directions, causing natural hazards such as earthquakes.
What is continental crust?
Older, lighter crust that cannot be destroyed, permanent.
What is oceanic crust?
New heavier crust that can be destroyed.
Describe the distribution of earthquakes and volcanoes.
Volcanoes are most commonly found along destructive plate boundaries and a place called the Ring of Fire which is found in and around the Pacific Ocean, and earthquakes are found and occur on all plate boundaries, however the severity of them depends on the type of boundary.
Describe the features of a constructive plate boundary.
Also known as the parting plate, it is when two oceanic crust pull apart. It causes gentle earthquakes and volcanoes, new crust is formed due to the magma that can rise up to the surface and cool, and an example of this is found in Iceland.
Describe the features of a destructive plate boundary.
It is when a continental crust and an oceanic crust collide, which causes violent earthquakes and volcanoes, it can also cause trenches and fold mountains and an example is it is found in the Andes Mountain Range and along the west coast of South America.
Describe the features of a collision plate boundary.
It is where two continental crusts meet and start rising together due to the pressure that they are generating, and it causes violent earthquakes but no volcanoes, and the Himalayas are being formed this way.
Describe the features of a conservative plate boundary.
Also known as the scraping plate, it is where two plates either scrape past each other or are travelling in the same direction but usually at different speeds. The plates get stuck, which often causes violent earthquakes but no volcanoes and an example of is found in the San Andreas Fault.
What is the epicentre of an earthquake?
It is the point on the earth’s surface directly above the focus. This is where the most damage from the earthquake is caused.
What is the focus of an earthquake?
The start of the earthquake within the crust.
What are the seismic waves of an earthquake?
They spread outwards away from the focus, the strength decreases as they travel further from the focus, and they make the rock contract and expand.
What happens as you travel further away from the epicentre?
The damage decreases with the distance from the epicentre.
What are the primary effects of earthquakes?
Ground shaking
Building collapsing
Ground splitting
What are the secondary effect of earthquakes?
Subsidence
Tsunamis
Contamination of water supplies
Disease
Gas leaks
Power outages
Fires
Floods
List the Christchurch earthquake figures:
Magnitude-6.3
Deaths-185
Injured-164
Buildings destroyed-100,000 buildings
Homeless-100,000
List the Haiti earthquake figures:
Magnitude-7
Deaths-316,000
Injured-300,000
Buildings destroyed-250,000 homes and 30,000 other buildings
Homeless-1,000,000
Why are the poor most at risk from earthquakes?
Construction
Poor medical facilities
No emergency plan prepared
Clearing up can be difficult due to lack of teams and workers.
What are the benefits of living in hazardous areas? (positive)
People who live in hazardous area can make huge amounts of money from the fertile oil from the volcano ash, the energy resources which don’t cause greenhouse gases to be produced (so it is good for the environment) and the mineral wealth from all the gold and diamonds that can be mined there.
What are the some procedures that can be prepared for the people living in hazardous areas?
People who live in hazardous areas should have a suitable emergency plan for either the volcano or earthquake. Also, they could choose to live by volcanoes which have been identified by a volcanologist as less or not active, meaning that it is less likely for the volcano to erupt so it is safer to live there.
How can we predict earthquakes?
Earthquakes are very unpredictable, which makes them very dangerous.
Observing animal behaviours
Seismographs
Tiltmeter
How can we protect against earthquakes?
We can make buildings earthquake proof, however higher income countries can achieve this better due to their greater wealth, so this means that the poorer countries are more at risk as they can’t protect themselves as well as the richer countries can.
How can we prepare for earthquakes?
Areas which are earthquake proof should have a full emergency plan put in place.
How do convection currents work?
Firstly, the heat source is made by the radioactive decay in the earths core, which heats up the mantle closest to the core. Then, the mantle rises because it has become less dense and lighter until it reaches the crust, where it cools down as it is far from the heat source. The liquid rock sinks down to the core to be reheated again. This movement of the mantle causes the tectonic plates to move, which causes natural hazards such as earthquakes and tsunamis.
