P1- Section A - Natural hazards and tectonic hazards Flashcards
What is the difference between natural events and natural hazards ?
Natural events have no risks whereas natural hazard pose potential risks of damage to property and loss of life .
How are different types of natural hazards classified ?
Tectonic Hazards-
Atmospheric Hazards
Geomorphological hazards
Biological hazards
What are tectonic hazards ?
Such as Earthquakes or tsunamis , which involve movemnt of tectonic plates in the Earths crust .
Examples of atmospheric hazards
hurricanes
examples of geomorphological hazards
ones that occur on the earths surface , flooding , glaciers , avalanches
example of biological hazards
such as forest fires , which involve living organisms .
Howis globalwarming a cause natural hazards ?
As it is warmer , more glaciers arre melting causing sea levels to rise , causing potential tsunamis , hotter climate caused droughts heatwaves , and warmer weather incresases the tempertaure of the oceans affecting marine species and ecosytems .
How is Deforestation a cause of Natural hazards ?
There arelos of trees on slopes , heavy storms could make tress collapse causing contamination in the water as soil could get into the sea and landslides .
How is Urbanisation a cause of natural hazards ?
More crowding in places means more poeple could be effected if an Earthquake hits and more builidng on impereable surfaces can increase flooding .
Why do people live in hazardous areas ?
CANNOT MOVE
due to living expenses ,
DONT WANT TO GO
Jobs
its worth staying due to the area (fertilised area due to a volcanic eruoton)
Overconfidenn in defences against hazards
Optimistic the hazard will not happen .
What are the four layers of the Earth (In layers starting from the outside )
Crust . Mantle , Outercore , Innercore
Describe the crust
Hard outershell that is cracked , the pieces are called plates . Very thin vompared to mantle and core
Describe the Mantle
Upper is hard but bellow that is semi-molten rock , 3800 degress celcius covers the core , made of material that flows very slowly (3800 degrees c ) the upper portion of the mantle is a weak layer called the asthenosphere .
Describe the Outer Core
Liquid Iron and Nickel
Inner Core
solid very hot - up to 5500 degress celcius
What aree the two types of crust ?
Oceanic Crust and Continetal Crust
Facts about Oceanic Crust
Under the ocean
5-10km thick
It is desner (think heavier ) than continetal crust
It is continually being renewed and subducted (destroyed )
It is mainly madeof basalt , made from solidified lava
Oceanic crust is young ;kss than 200 millioon years .
Facts about Continental Crust
25-100km thick
It is less dense (2.7g/cmcubed) than the oceanic curst
Cannot sink or be destroyed
It is older than Oceanic crust - 3.8Billion years old
Mainly made of granite rocks (lower part maily basalt and diorite )
What is the Earth’s structure (inwards out )
At the center is the core , (descrbe both cores ) then mantle (describe mantle ) , outermost layer is *crust * (describe crust )
what do the crust and mantle form
They from a rigid shell on the surface of the earh called the lithosphere .
What is significant about the lithosphere
The lithosphere is broken into bits called tectonic plates which move very slowly across the upper mantle . Movement can be tracked using gps .
How do tectonic plates move
There are two theories
convecton
or slab pull (ridge push ) - more accepted explanation
Describe convection
The core’s temerature is around 6,000 , this causes magma (molten rock ) to rise in the mantle and sink towards the core when it cools . The currents flowing beneath the lithosphere , nuilding up lateral pressure and carrying the plates with them . However only liited evidence about cc has been found so far .
Describe Slab pull
At constructive margins ocean ridges from high above the ocean floor . Beneath ocean ridges , the magma melts . the molten magma rises as the playes move apar and cools down to form new plate material . As the lithosphere cools , it becomes denser and starts to slide down awy from the ridge which causes the plates to move away from eachother .
What is it known where two plates meet
A plate margin
What are four different plate margins
constructive
destructive
conservative
collison
What does interactions between different tectonic plates adn the mantle trigger ?
Earthquakes and volcanic activity .
Where are Earthquakes and volcanicoes located
Uusually where plate margins are located
where are earthquakes specifically located ?
are found on all three plate margins
where are volcanoes specifically located ?
on constructive ad destructive plate margins .
What are the band of volcanoes and earthquakes which run along the west coast of north and south american known as where is it
It circles the pacific ocean and is known as the ring of fire .
What are the earthquakes that occur in the middle f plates known as - example ?
They are known as hotspots , hawaii has formed due to volcanic erruptions at a hot spot located far from the dge of the pacific ocean
What direction to plates move in constructive plate boundaries
move away from eachother
what type of crust is in constructive plate boundaries
oceanic crust
Why are earthquakes and volcanoes found at constructive plate margins ?
- At constructive margins , the upper part of the mantle melts and the hot molten magam rises
- As the tectonic plates are moved away from eachotherby slab pull , rdge push or a combination , the motlen magma rises between nd coolds don to form oslid rock . This forms part of the ocenaic plate .The new solid plate sometimes is fractured s it is moved causing earthquakes .
- Much of the magam never reaches the surface is buoyant enouh to form ridges . Om a few placces magma erupts onto the surface producing lava tha t is runny and spreads out before solidygin , A shield volcanoe forms 0 ha wide base and gentle slope .
Example of contructive plate margins
Midatlantic ridge . North ameircan plate and eurasian plte runs thorugh the middle of atlantic ocean extedns to iceland .
Another thing ridges can do ? example
ridges can form isalnds - the azore islands in the atlantic oceans
How could you tell that mid atlantic ridge is constructive plate margin ?
The strain put on the lan as tectoic plate move away from eachother caises cracks or faults to form on eather side .
Are earthquakkes experienced at constructive plate margins explain ?
At a constructive plate margin the plates move apart from one another. When this happens the magma from the mantle rises up to make (or construct) new land in the form of a shield volcano. The movement of the plates over the mantle can cause earthquakes. The new solid plate sometime frctures as it is moved , causing earthquakes .
Wha direction do plates move in destructive pate boundaries ?
They move towards eachother .
What crust is involved in destructive plate boundaries
Oceanic and continental crust .
What type of plate boundary is destructive plate boundary why ?
Convergent plate boundary as convection currents move towards echother .
Explain destructive plate boundaries
Convection currents move towards eachother
2. this movment generates friction between the convectoin currents and pltes and drags the plates towards eachother .
As oceanic plte is denser thhan continetal plate , the oceanic plate is subudcted .
As it is subducted it rubs causing earthquakes known as the benioff zone .
The part of the oceanic plate that is subducted under the continetal crust becomes superheated and melts .
This causes magma to rise upp underneath the continetal plate and starts to fill magma chamber
Hot magma rises through the the overlying mantle and lithosphere and some can evenrually errupt producing aa linea rbelt of volcanoes .
A trench is also formed where the oceanic crust is subducted .
Mountain ranges = destructive plate boundaries ?
The pressure of the oceanic plate pushing into the continetal plate , bends and folds the continetal plate , which is why we get veyr long mountain ranges .
example of a mountain rnage due to destructive plate boundary
Rocky mountains - north america
example of a trench due to destructive plate boundary
Marinas trench - philliphnes
example of volcanoe formed on contintal plate
Mount ST Helens
What is the moevemnt of plates in conservative plate boundaries
Two plates have atranfrom plate movemnt , a conservtive plate margi occrus when tectonic plates move parallel to eachohter .
What are the the 2 ways conservative plate boundareis can move ?
In opposite directions
same diretion but at different different speeds
Why dont volcanoes occur on conservtive plate boundaries
There is no volcanoes as magma cnnot rise to fill a graph as there is no grpah created between the tectonic plates and therefore there is no new land formed . Neither is any land destroyed as no tectonic plate is subducted into the mantle .
Why are Earthquakes founda t conservatie plate margins ?
As the plates slide pst eachother , friction causes them to become stuck . Friction builds up and up until eventually the rock fractures in an earthquake .
where is the focus of the earthquake in a conservative plate boundary ?
The foucs of an earthquake is tupically the area of friction ina conservative plte boundary .
example of conservtive plate boundary
san andreas fault - paciifc plte and north maerican plte , moving in same direction but pacific plate i moving faster (6cm) north american is moving (1cm)
What type of plate boundary is collions plate boundary why
convergent plate boundary - beacuse they move towards eachotehr
What are coservaitve the plates made of why ?
The plates have ot be the same density ,
continental +continental or
oceanic +oceanic
Explain collision plate boundaires
C.c move toward eachother which geneartes friction between c.c and earth’ crust .
Friction drgas plates twoards eachother , because they have the same density and cannot subduct , so they collide and squash together creating fold mountains .
Example of collison plate boudnaries
Himalayals - Indian plate and eurasian plte - two continetal crusts .
