Challenges of natural hazards - teconic hazard Flashcards
What is the eraths structure?
the earth is composed of 4 main layers:
-The inner core which is a dense solid layer which is under a ot of pressure. Composed of iron and nickel. Temp around 5500 degrees
- The outer core which is a semi molten layer with temps around 5000-5500 degrees
- the mantle which is a semi molten layer that surrounds the core. The upper portion of the mantle is a weak layer called the asthenosphere which can deform like plastic
- teh crust is the outermost layer of the earth and there are 2 types: oceanic and continental crust
what is the difference between oceanic and continental crust
-Oceanic crust is thinner but much heavier and denser than the continental crust hense why it is the one which subducts and is constantly getting destroyed. It is formed by basaltic rock.
- continental crust is older but thicker and lighter than the oceanic crust because it is not destroyed.
What is the rigid shell on the surface of the earth formed by the upper mantle and crust called?
lithosphere
Tectonic plates are broken fragrements of what?
lithosphere
what is the name given when 2 plates meet?
plate margin
what are the 3 main types of plate margins>
destructive, conservative and constructive
what are each of the plate margins?
-Destructive: It can happen between 2 continental or one of each.
If 2 continental plate margins colide, there is no subduction due to no difference in density. Insead they become crumpled and uplifted with pressure between the 2 plates, this results in the creation of fold mountains. This collision causes earthquakes but no volcanic erruptions due to no magma present
If one of each crust collides, the oceanic crust subducts under the continental crust. This causes the pressure of magma to build up and force its way up through the cracks of the rocks and rises up through composite volcanoes. Causing colcanic erruptions and easrthquakes.
- At a conservative plate margin, the plaate move past each other in the same direction but at different speeds or in opposite directions. They form earthquakes but not volcanoes.
-contructive plates are when 2 plates move away from each other and when the plates move apart, magma rises between the gapes which then pours onto the surface and the lava dries up, forming volcanoes. Earthquakes can also happen due to the vibration when the plates move apart. This process can happen both on oceanic and continental crust.
On land, they can form steep sided rift valleys and in oceans, new land can be formed and this is known as sea floor spreading.
At the same time volcanoes form on constructive plate margins but wekaer erruptions happen becasue the magma barely reaches onto the crust.
why do conservative plate margins cause earthquakes?
when the sliding happens, pressure builds up between the plates and eventually it becoems so large that the plate moves ina. sudden jolt and the plates slip and shift, causing large amounts of energy to be released and this sends vibrations through the grounds and causes an earthquake. On an oceanic crust or in the ocean, this can displace large amounts of water and create tsunami. No volcaoes are formed as no magma is generated and no gaps for the magma to rise.
Why are both earthquakes and volcanoes found on destructive plate margins?
As the plates colide, pressure builds up and eventually the rocks fracture and causes an earthquake . Similarly, when the oceanic crust subducts it leaves a deep ocean trench and causes part of the mantle to melt, creating magma. The magma rises and creates pressure with some eventually errupting out of the surface producing a linear belt of volcanoes. This causes violent erruptions.
what is a tectonic hazard?
the threats that are caused by the movement of tectonic plates that have the potential to cause damage to life, property and the environment.
What are the 2 theories responsible for the movement of tectonic plates
Convection and slab pull and ridge push
what is the convection currents.
when plates move due to the movent of the magma which creates convection currents. The cores temp casues hotter and less dense magma to rise and the sink back down towards the core when it reaches the top and becomes cooler (denser) However there has only be limit evidence supporting this
what is the slab pull ridge push
this is the process which drives the mantle convection instead of the other way around.
During ridge push, the plate moves apart and the magma rises. Then the magma cools and forms new plate material. It becomes denser as it cools and slides away from the ridge, causing plates to move away fro each other.
During slab pull, the denser plate sinks back into the mantle due to gravity and pulls the rest of the plate with it.
General distribution of earthquakes and volcanoes
- occurs on plate margins.
- earthquakes and volcanoes can be found both on land and sea
- earthquakes can be found along all types of plate margins but volcanoes can only be found on destruction and constructuve plate margins.
-Large band of earthquake and volcanoe circling the pacific plate is the ‘ring of fire’
-The belt of volcanoes throigh the mid alantic ocean is called the mid alantic ridge
what are the effects and responses of tectonic hazards?
Primary effects =P
Secondary effects =S
effects:
-intense shaking of ground (P)= tsunamiis (S)
-injuries and people being killed (P)= trauma and loss of income as peoples livlihoods are destroyed (S)
- Infrastructire destroyed (P) = homlessness and social disorder/conflicts (S)
responses:
1) immediate:
- providing food and water