Tectonic Hazards Flashcards
Different layers of the earth and their key characteristics
Inner core- This part of the core is solid
Both the outer and inner core are made up of metal, mainly iron mixed with nickel
Only 1260km thick
This is the hottest part of the earth
Outer core- Both the outer and inner core are made up of metal, mainly iron mixed with nickel
About 2220km thick- thicker than the inner core
This part of the core is a liquid
Mantle- Thickest part of the earth at about 2900km thick
The outer mantle is hard, but further in it is like soft toffee
This is made of denser (heavier) rock than the crust
Crust- We live on this layer
Made of less dense (lighter) rock so floats on the mantle
This is the thinnest layer, ranging from 8-65km thick
This is the Earth’s hard skin
Continental crust & Oceanic crust
Continental crust- Makes up land masses Less dense (lighter) Thicker - on average 20-50km thick Mainly made of granite Oceanic crust- Forms on the ocean floor Denser (heavier) Thinner - on average 7km thick Mainly made of basalt
describe the main processes and landforms associated with the following plate margins: constructive (divergent),
Constructive: moving away from each other, two plates diverging above the upward plume of a convection call. Magma rises through the gap between the two plates, resulting in volcanoes. The erupted lava cools, and solidifies to form new crust. Along the mid-Atlantic Ridge much of this takes place below the ocean surface, forming a mid-ocean ridge. When a volcano breaks through the ocean surface, it creates a volcanic island such as Iceland. Eruptions and earthquakes along constructive margins tend to be relatively gentle.
describe the main processes and landforms associated with the following plate margins: destructive (convergent)
Destructive margins occur where two plates, one made of oceanic crust and one made of continental
crust, are converging. When the two plates meet, the oceanic plate dives beneath the continental plate, because it is denser. This process is known as subduction. The continental crust can buckle upwards, creating a range of fold mountains. The sinking plate can get ‘stuck’ due to friction, leading to a build up in pressure. This pressure is released in a sudden slippage of the plates, resulting in powerful earthquakes. The friction also generates a lot of heat, causing the descending crust to melt. This creates extra magma which rises to the surface through cracks in the rock, resulting in violent volcanic eruptions.
describe the main processes and landforms associated with the following plate margins: collision (convergent)
A collision margin occurs when two plates made of continental crust converge. Because neither plate is denser than the other, subduction does not occur. Therefore, the plates simply buckle up to create a range of fold mountains. There are no volcanoes along collision margins, because there is no rising magma, but very powerful earthquakes do occur.
describe the main processes and landforms associated with the following plate margins: conservative
Conservative plate margins occur where two plates move parallel to one another in opposite directions or in the same directions. At the Sun Francisco Fault in California, both plates are moving in a northwesterly direction, but the Pacific Plate is moving faster than the North American Plate. Friction can cause the two plates to stick, and pressure builds up. When the plates slip, this pressure in released as a powerful earthquakes (e.g. San Andres in 1906 and 1989). There are no volcanoes on conservative margins, because there is no rising magma.
At a constructive plate boundary you see…
Volcanoes because it creates volcanic islands
At a destructive plate margin you see…
Both earthquakes and volcanoes
convection currents, along with their effect on the earth’s plates.
The core heats up the mantle and as heat rises the magma rises, and goes up towards the crust and loses heat as it is further away from the heat source, and it goes into a cycle and creates a circular motion. The circular motion creates a drag which causes the tectonic plates to drag as the plates are floating on the mantle and causes the continents to move. The magma in the mantle sinks when it is cooled
Distribution of earthquakes and volcanoes around the world
The volcanoes are found in a linear pattern around the plate boundaries
The earthquakes and volcanoes are unevenly distributed
There is a high concentration of volcanoes and earthquakes on the west coast of South America and the South West of North America
There is a high concentration of volcanoes and earthquakes along the boundary of the Pacific plate but not in the centre of the plate
Why do earthquakes happen?
At plate boundaries, earthquakes occur when energy, which has been stored up by rocks which are locked together, is suddenly released when the pressure gets too much. Before the energy is released it is known as strain energy. It is then released in waves called seismic waves. These waves pass through the earth causing shaking.
What is happening at each plate boundary to cause and earthquake
Conservative – The plate are moving parallel to each other. The plates can get stuck which causes pressure to build up. When the plates slip this pressure is released in the form of an earthquake.
Destructive – An oceanic and a continental plate are moving towards each other. The oceanic plate is denser than the continental plate and is therefore subducted beneath the continental plate. Pressure builds up and this is released in the form of an earthquake
Collision – Two continental plates are moving towards each other. The plates buckle upwards and pressure builds up. This pressure is eventually released in the form of an earthquake.
Earthquake
A sudden, brief and intense shaking of the ground cause by stress accumulating in the Earth’s crust that causes rocks to fracture and slip
Focus
The point within the Earth’s crust where the rocks slip along a fault line; seismic waves radiate out from this point.
Epicentre
The point on the Earth’s surface immediately above the focus; in theory, this is the place that experiences the strongest shaking, as the seismic waves have the shortest distance to the surface to travel and therefore lose least energy on the way
