Tectonic Hazards Flashcards
Describe how Tectonic Plates move according to the convection current theory
(BLURT QUESTION)
- The CORE heats up the MAGMA in the MANTLE
- The HOT MAGMA is LESS DENSE than that in its surroundings so it RISES
- When it REACHES the TOP the magma COOLS
- It becomes MORE DENSE so COOLS and SINKS
- It is REHEATED and the CYCLE continues
- The PLATES are pushed and pulled by the convection currents
What is the global distribution of Earthquakes and Volcanoes?
(BLURT QUESTION)
-Occur along tectonic plate boundaries
-Along the Ring of Fire
What is the Ring of Fire?
(BLURT QUESTION)
-A TECTONICALLY ACTIVE area around the Pacific Ocean
-It follows the BOUNDARIES of the PACIFIC PLATE which has FREQUENT SUBDUCTION ZONES
-Countries included are Japan, USA, New Zealand, Chile…
Why might some Volcanoes NOT form along plate margins?
-Hotspots are areas where magma breaks through the plate and up to the surface.
E.g Hawaii
What happens at a Constructive Plate Margin?
(BLURT QUESTION)
-Plates move APART from each other
-MAGMA RISES in between the GAP left by the PLATES
-Lava POURS onto the SURFACE
-VOLCANOES FORM in the AREAS where LAVA POURS OUT, usually shield volcanoes
What happens at underwater Constructive Plate Boundaries?
-Seafloor Spreading
-> the creation of new oceanic crust due to molten magma
->this can cause islands to form as the rock builds up
What happens at inland Constructive Plate Boundaries?
-Rift Valleys are formed
-> A lowland areas caused by huge land fractures
E.g The East African Rift Valley
What happens at Destructive Plate Margins?
(BLURT QUESTION)
-The plates move towards each other
-The Oceanic Crust is SUBDUCTED below the thicker, lighter Continental Crust
-The plate that is SUBDUCTED leaves a deep OCEAN TRENCH
- FRICTION between the two plates causes STRONG, DEEP EARTHQUAKES
-The OCEANIC CRUST is MELTED as it is PULLED DEEPER into the MANTLE which creates MAGMA
-This MAGMA causes PRESSURE to build up beneath the CRUST
-Eventually, the MAGMA breaks through the crust, forming EXPLOSIVE VOLCANOES
What happens when two oceanic plates move towards each other?
The DENSER plate is SUBDUCTED. Underwater islands form such as the Marina Trench.
What happens when two continental plates move towards each other?
-The plates CANNOT SUBDUCT so they CONTINUE to move towards eachother
-This causes the land to CRUMPLE UPWARDS
-This creates FOLD mountains.
What happens at Conservative Plate Boundaries?
(BLURT QUESTION)
-Parallel plates MOVING in DIFFERENT DIRECTIONS or SPEEDS
-When these plates move side by side FRICTION BUILDS
-As these plates move past eachother
-Eventually the PRESSURE becomes so LARGE that the plates UNSTICK and move in a SUDDEN JOLT
-This releases lots of energy which sends vibrations through the ground. This causes EARTHQUAKES.
What happens when two Continental Crusts move alongside eachother?
Faultlines occur where the ground cracks from movement.
What happens when two Oceanic Crusts move alongside eachother?
Tsunamis due to displaced water.
What are some Primary Effects of tectonic hazards?
-Intense SHAKING off the GROUND
-INFRASTRUCTURE and HOMES DESTROYED
-Injuries
-People KILLED by DAMAGED BUILDINGS or by HOT ASH and GAS from a VOLCANO
-DAMAGED electricity, water and communications (e.g telephone lines)
What are some Secondary Effects of Tectonic Hazards?
-Mudflows
-Avalanches
-Tsunamis
-Homelessness
-Loss of Incomes
-Conflict
Some tectonic hazards are beneficial to a population because…
- Near volcanoes the soil is very fertile
-> this is immensely useful for profiting from agriculture
-Tourism
-> creates job opportunities, e.g Guides around Mount Etna, a very active volcano in Italy
Sometimes the threat of tectonic hazards can be overlooked because…
(BLURT QUESTION)
-Hazards are MONITORED and MANAGED
->Some places have ADAPTED to tectonic hazards which DECREASES the HAZARD RISK
->EARTHQUAKE-PROOF-BUILDINGS and WARNING SYSTEMS have allowed for IMPROVEMENTS in the EVACUATION and SURVIVAL RATES of a population during a tectonic hazard
->e.g Japan
Some tectonic hazards might seem insignificant because…
-They are very INFREQUENT
-> Some of the LARGEST CITIES in the world, such as California, sit on PLATE BOUNDARIES.
Some people do not have a choice to live in an area of Tectonic Risk because of…
-POVERTY and EDUCATION
->Some people are UNABLE to AFFORD to MOVE AWAY
->Some may not be EDUCATED on the RISKS of the AREA and hence are actually UNAWARE they are in DANGER
When discussing Hazard Management, what is meant by Monitoring?
Detecting and recording physical changes and warning signs
What is meant by Predicting?
Using monitoring and historical trends to predict if and when a tectonic event might occur
What is meant by Protecting?
Increasing the resistance of a population to a hazard by physically designing things that will withstand hazards.
What is meant by Planning?
Having systems in place to prepare a population in advance
How do scientists monitor tectonic hazards?
They monitor changes in the area surrounding fault lines and volcanoes to see how far away a hazardous event might be
How do Tiltmeteres help to predict and monitor earthquakes?
MEASURES the TILTING or SWELLING of the GROUND as STRESS BUILDS near FAULT LINES
(ground deformation near fault lines)
What are fault lines?
Cracks in the crust
How do GPS devices help to predict and monitor Earthquakes?
MONITORING:
Tracks plate movements
PREDICTION:
This gives insight into where earthquakes will/could occur
How do Seisometers help to predict and monitor Volcanoes?
MONITORING:
Monitor volcanic earthquakes caused by magma movement
PREDICTION:
Can signal building pressure, potentially leading to an eruption
How does Gas Monitoring help to predict and monitor Volcanoes?
MONITORING:
Increased gas emissions indicates increased volcanic activity
PREDICTION:
This could signal an impeding eruption
How can people be protected from tectonic hazards?
-Concrete blocks and explosives can be used to DIVERT or SLOW lava flows
-Earthquake proof buildings which have shock absorbers and strengthened foundations are built
How can planning help people at risk?
-Hazard Mapping
->DIVIDING hazardous areas by LEVEL of RISK and using land accordingly
->Therefore necessities such as HOSPITALS can be built FAR from FAULT LINES and VOLCANOES
-Coordinating Evacuation Routes
