Tectonics Flashcards
What are that x4 processes that drive tectonic plate movement?
- Mantle Convection
- Sea Floor Spreading
- Slab Pull
- Subduction
What is a natural hazard?
A naturally occurring process or event that has the potential to affect people
What is a natural disaster?
A major natural hazard that can cause significant social, economic and environmental damage to a vulnerable population
What is vulnerability?
The ability to anticipate, cope with, resist and recover froma natural hazard
Why is Nepal vulnerable to natural hazards?
- Monsoon rain
- Poor infrastructure
- Excessive snow melt
- Poor technology
- Poor economy
- Located on a plate boundary
- Relief rainfall
What is the inner core?
- Hottest part of the Earth - heat is generated by radioactive decay
- Solid due to extreme temperatures & pressure
- Consists of ion
What is the outer core?
- Temperatures range from 4500 to 6000
- Semi molten
- Consists of liquid iron and nickel
What is the mantle?
- Cooler
- Semi molten
- Consists mostly of silicates
- Thickest layer
- Upper mantle can be split into two layers - lithosphere and asthenosphere
What is the crust?
- Temperatures range form 200 to 400
- Solid
- Thinnest layer of the Earth’s structure
- 2 types of crust - oceanic (thin and dense) and continental (thicker, older & less dense)
What is the lithosphere?
Thin solid layer where tectonic plates are formed
What is the asthenosphere?
Semi molten layer which tectonic plates ‘float’ upon
What is mantle convection?
- Long thought to be responsible for plate movement
- Heat produced by the decay of radioactive elements in the core eats the lower mantle - creating convection currents
-These cause the plates to move
What is slab pull?
- Increasingly seen as a major driving force for plate movement
- Newly formed oceanic crust at mid-ocean ridges becomes denser and thicker a it cools
- This causes it to sink into the mantle under its own weight pulling the rest of the plate further down with it
What is subduction?
- As new crust is being created in one place, its being destroyed in another - by subduction
- As two oceanic plate move towards each other, one slide under the other into the mantle - where it melts in an and are known as a subduction zone
What is seafloor spreading?
- In the middle of many oceans are huge made-ocean ridges, or underwater mountain ranges
- These are formed when hot magma is forced up from the asthenosphere and hardens - forming new oceanic crust
- The new crust pushes the tectonic plates part in a process called seafloor spreading
What is paleomagnetism?
The study of past changes in the Earth’s magnetic field
What is a plate boundary?
Place on Earth’s crust where two or more plates meet
What is a plate margin?
The area either side of the plate
What is a Benioff Zone?
Area where plates make contact and friction occurs - results in an earthquake
What is an Island Arc?
A long chain of active volcanoes with intense seismic activity found along convergent plate boundaries?
What is a Mid-Ocean Ridge?
Seafloor mountain system formed at divergent plate boundaries
What is a Rift Valley?
Steep-sided valley formed at divergent plate boundaries when the land between faults collapses
What happens at convergent plate boundaries?
- Plates move toward each other
-3 types
-Oceanic meets continental
-Oceanic meets oceanic
-Continental meets continental
What happens at divergent plate boundaries?
- 2 plates move apart
-Leads to formation of new crust - Forms mid-ocean ridges and rift valleys
What happens at conservative plate margins?
- Two plates slide past each other
-Results in major breakage in the crust between them
-Break is called fault or transform fault - Tectonically very active
- Associated with powerful earthquakes
- Can sometimes stick together
-Suddenly released as a strong. shallow focus earthquake
What is the focus of an earthquake?
The point inside the crust from which the pressure is released
What is the epicentre of an earthquake?
The point on the surface directly above the focus. This is where the most shaking and damage occurs
What are primary seismic waves?
- Body wave
- Fastest and first to reach surface
- Travel through solids and liquids
- Only damaging in the most powerful earthquakes
What are secondary seismic waves?
- Body wave
- Slower (60% slower than P waves)
- Only travel through solids
- Do more damage than P waves
What are love seismic waves?
- Surface wave
- Slowest
- Cause most damage
- Larger
- Focus all energy on the Earth’s surface
What is earthquake magnitude?
Measures the amount of energy released at the epicentre
What scale is used to measure magnitude?
Moment Magnitude Sale
What is earthquake intensity?
An earthquakes effect on people, structures and the natural environment
What scale is used to measure earthquake intensity?
Modified Mercalli Intensity Scale
What are the physical impacts of an earthquake?
- Magnitude and depth
- Distance from epicentre
- Geology
- Coastal location
- Topography
What are the human impacts of an earthquake?
- Country’s level of development
- Population size/density
- Level of preparation
- Effectiveness of response
What are primary effects?
Effects that happen as a direct result of an earthquake, such as :
- Ground shaking
- Crustal fracturing
What is ground shaking?
This causes building, bridges, roads and infrastructure to collapse, killing or injuring those nearby
What is crustal fracturing?
When energy released during an earthquake causes the crust to crack, leaving large gaps behind
What are secondary effects?
In many earthquakes, secondary effects cause as much damage than the initial shacking. These include:
- Liquefaction
- Landslides & Avalanches
- Tsunamis
What is liquefaction?
Violent shacking during the earthquakes causes the surface rocks to lose strength and act more like liquid
What are landslide & avalanches?
The ground shacking puts stress on slopes which eventually causes them to fail
