Chapter 1 Gateway 1: Plate Tectonics Flashcards
What is a natural hazard?
A naturally occurring event that threatens human lives and causes damage to property
What can a natural hazard be?
- Tectonic
2. Climate-related
What is the impact of natural hazards
Natural hazards can impact places at different scales
What are tectonic natural hazards caused by?
Plate movements when continental crusts and ocean floors move
What are examples of tectonic natural hazards?
- Earthquakes
2. Volcanic eruptions
Where are tectonic natural hazards concentrated?
The occurrence of many tectonic hazards such as earthquakes and volcanic eruptions is mainly concentrated near the coastlines of the Pacific Ocean
What are climate-related natural hazards caused by?
Severe and extreme weather and climate conditions
What are examples of climate-related natural hazards?
- Floods
- Droughts
- Storms
- Tropical cyclone
Where are climate-related natural hazards concentrated?
Climate-related natural hazards such as floods, droughts, storms and tropical cyclones are widely distributed. They are found in the Pacific Ocean, Atlantic Ocean, Indian Ocean, North America, South America, Africa, Australia and Asian regions
What are the three main layers of the earth?
- Core
- Mantle
- Crust
Where is the core located?
Centre of the earth
How thick is the core?
3500 kilometres thick
what is the core composed of?
Mostly of iron and nickel
What is the core made up of?
- Inner core
2. Outer core
What is the temperature of the core?
3000-5000 degree celsius
What is the state of the inner core? Why?
Solid
The extreme pressure exerted on it by the surrounding layers
How thick is the inner core?
1200 kilometres thick
What is the state of the outer core?
Liquid
How thick is the outer core?
TBD
Where is the mantle located?
Above the core
How much does the mantle occupies?
Occupy 80% of the earth’s total volume
How thick is the mantle?
2900 kilometres thick
What is the mantle composed of?
Mostly of solid rock that flows under high temperature and pressure
What is the mantle made up of?
- Upper mantle
2. Lower mantle
What is the state of the upper mantle?
Solid
What is the state of the lower mantle?
Molten
What is lithosphere? Description?
The outer part of the mantle along with the overlying crust
Rigid and brittle, floats on the softer asthenosphere
What is asthenosphere? Description?
Weak sphere
Where high temperatures and pressure bring the rocks close enough to their melting point for them to be easily deformed
Where is the layer of the crust?
Earth’s outermost layer
How thick is the crust?
5 to 70 kilometres thick
How is magma formed?
When the rocks in the lithosphere melt
What are the types of crust?
- Oceanic crust
2. Continental crust
Where is the oceanic crust located?
Beneath deep oceans
How thick is the oceanic crust?
5 to 8 kilometres thick
What does the oceanic crust consist of?
mainly of basalt
What is the age of the oceanic crust?
Rocks that are lesser than 200 million years old
Where is the continental crust located?
Beneath the earth’s continental land masses and under shallow seas close to continents
How thick is the continental crust?
35 to 70 kilometres thick
What does the continental crust consist of?
Lighter rocks, including granite
How old is the continental crust?
Very recent to nearly 4 billion years old
Why tectonic plates move?
- Convection currents are movements of heat in the mantle. Material in the mantle is heated by the core, causing the mantle to heat up, rise and spread out beneath the plates
- This causes plates to be dragged along and to move away from each other
- Then, the hot mantle material cools slightly and sinks, pulling the plates along
- The sinking mantle material heats up again as it nears the core and the whole process repeats
- Slab-pull force occurs when the dense, sinking oceanic plate at subduction zones pulls the rest of the plates behind it. This is currently the main driving mechanism for plate movement
- The subduction or sinking plate drives the downward-moving portion of convection currents
- The mantle material which is found far away from the plates subduct drives the rising portion of convection currents
What is divergent plate boundaries?
Areas where the plates move away from each other
When does oceanic plates form?
Magma moves upwards to the surface where it cools
What does divergent plate boundaries include?
- Southern boundaries of the australian plate
2: Southern and eastern boundaries of the pacific plate
Where are divergent plate boundaries found?
- Oceanic-oceanic plate boundaries
2. Continental-continental plate boundaries
Example of oceanic-oceanic plate divergence
Mid-Atlantic ridge in the middle of the Atlantic Ocean was formed when the North American plate and the Eurasian plate moved away from each other
Convergent plate boundaries
When two plates move towards each other and become faulted, folded and sometimes subducted
Example:
North of the pacific plate and the North American plate
Between the Philippine plate and the Eurasian plate
Found:
Oceanic-oceanic plate boundaries
Continental-continental plate boundaries
Oceanic-continental plate boundaries
Oceanic-Oceanic Plate divergence process
Convection currents drag the oceanic plates above it and cause it to diverge. As the plates diverge, fractures are formed at the plate boundary. Magma rises at the zone of divergence. The lava cools and solidifies and new sea-floor is formed. This process is called sea-floor spreading. The newly formed rocks are closest to the plate boundary and the older rocks are further away. When two plates diverge, a mid-oceanic ridge is formed. The layers of lava cool and solidify to form undersea volcanoes. Over time, lava builds up above sea level to form volcanoes known as volcanic islands
Continental-Continental Plate divergence process
Convection currents drag the continental plates above it and cause it to diverge. Due to tensional forces, they are stretched and faults are formed at the plate boundary. When sections of the crust extend along fault lines, the central block of land subsides between a pair of parallel faults forming a linear depression known as a rift valley
