Natural Hazards Flashcards
Name each layer of the Earth from centre outwards
Inner core; outer core; mantle; crust
How many tectonic plates are on Earth?
7
What are the two types of Earth’s crust and what are their properties?
Continental crust - older, lighter, permanent;
Oceanic crust - younger, heavier, destroyed and replaced
Name the four different plate boundaries
Destructive; constructive; collision; conservative
What happens at a destructive plate boundary?
Continental crust collides with oceanic crust. The heavier oceanic crust sinks into the mantle and melts through subduction. Pressure builds, creating earthquakes. A large volcano forms from the melted oceanic crust and mantle and there are violent eruptions.
What happens at a constructive plate boundary?
This only happens underwater when two oceanic crusts move apart. The plates separate, releasing a gentle volcano. The magma solidifies, creating more crust. Gentle earthquakes are also found here.
What happens at a collision plate boundary?
Two continental crusts collide, creating violent earthquakes. Both plates buckle upwards, creating mountains.
What happens at a conservative plate boundary
The plates slide past each other, all of the building up pressure creating earthquakes.
How do plates move?
Convection currents work as parts of the liquid mantle heat up near the core and rise. They then travel along the crust, dragging it along slightly, cooling as they go. When they cool down so much, they will fall and repeat the process.
What is the epicentre of an earthquake?
The point on the surface closest to the focus.
What is the focus of an earthquake?
The built up pressure where the earthquake originated.
What are seismic waves?
The earthquakes energy travelling outwards in waves.
What is the Mercalli Scale?
A 12 point scale that measures earthquakes by describing the DAMAGE that can be seen afterwards.
What is the Richter Scale?
A 12 point scale that describes the MAGNITUDE or POWER of the earthquake, measured by a seismometer. Note that the Richter Scale is logarithmic.
What magnitude reading on the Richter scale does it have to exceed for it to be classified as an earthquake?
5
Case study: Christchurch
When did it happen?
12:51pm, 22nd February, 2011
Case study: Christchurch
Where did it happen?
Christchurch, New Zealand
Case study: Christchurch
What was the magnitude of the earthquake?
6.3
Case study: Christchurch
How many people were killed and how many seriously injured?
185; 164
Case study: Christchurch
What is liquefaction?
When the earthquakes vibrations cause underground water to be brought to the surface, turning the ground to thick, muddy slush.
Case study: Christchurch
How many buildings were damaged?
About 100,000, leaving over 10,000 homeless
Case study: Christchurch
What was the response like?
A plan of action was in place within 2 hours. Many countries came to help as well as many organisations bringing thousands of volunteers including farmers with machinery and students to clear up liquefaction.
Case study: Haiti
When did the earthquake take place?
Tuesday the 12th January 2010, at 16:53
Case study: Haiti
Where did the earthquake happen?
Haiti, the western third of the Caribbean island of Hispaniola in North America between the Caribbean Sea and the North Atlantic Ocean