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Living with Tectonic Hazards - Coggle Diagram
Living with Tectonic Hazards
Natural Hazard
Definition:A naturally occurring event that threatens human lives and causes damage to properly
Tectonic
Caused by plate movements
Climate-related
Caused by severe and extreme weather and climate conditions
Internal Structure of the Earth
Mantle
Mostly solid rock that flows under high temp. and pressure
2900km thick
Temp. between 800-3000 degree Celsius
Crust
Basalt and granite rocks
A few km to more than 70 km thick
Core
Temperature 3000-5000 degree Celsius
About 3500km thick
Separated into liquid outer core and solid inner core
Mostly iron and nickel
Tectonic Plates
What is it?
Oceanic crust
Between 5-8km thick
Consists mainly of basalt, a heavy and dense rock formed from magma which has cooled quickly
Beneath deep oceans
Rocks of less than 200 million years old
Continental Crust
Between 35-70km thick
Consists of lighter rock, including granite
Beneath the earth's continental land masses, under shallow seas close to continents
Wide range of rock ages, from very recent to nearly 4 billion years old
Mixture of both crusts
Why do they move?
Convection currents
and movements of heat within the mantle. Mantle material is heated by the core, it expands, rises and spread out beneath the plates
Causes plates to be dragged along and move away from each other
Hot mantle material cools slightly and sinks, pulling the plates along
Sinking mantle material heats up as nears the core and the whole process repeats
Slab-pull force
occurs when the dense, sinking oceanic plates at subduction zones pull the rest of the plate behind it
Plate Boundaries
Eurasian Plate
Pacific Plate
African Plate
Indian Plate
South American Plate
Australian Plate
North American Plate
Philippine Plate
Nazca Plate
Plate Movements
Convergent Plate Boundaries ===>|<===
Oceanic-Oceanic
The subducted oceanic plate causes mantle material above it to melt , forming magma
The magma rises through the crust and form volcanoes. Eventually, a chain or arc of islands is formed
A
deep oceanic trench
is formed at the subduction zone
Earthquakes may occur at the boundary between the 2 plates due to friction created between the moving rock masses when a plate subducts under another
Denser oceanic plate will subduct beneath the less dense oceanic plate when 2 oceanic plates converge and collide
Example: Oceanic Pacific Plate converges and subducts beneath the slower-moving oceanic Philippine Plate, forming the Mariana Trench and Mariana Islands
Continental-Continental
When 2 continental plates converge and collide, crusts are compressed and causes massive folding
Folding of the crusts causes massive folding
Example: Continental Indian Plate and Continental Eurasian Plate converges, forming the Himalayas fold mountains
Both plates are too thick and buoyant for subduction to occur, instead they collide and push against one another, resisting subduction
Oceanic-Continental
The edge of rocks on the continental plate buckles and folds,
forming fold mountains
The subducted oceanic plate causes the
mantle material above it to melt, forming magma
A
deep oceanic trench
is formed at the
subduction zone
The magma
rises through the crust
, giving rise to
volcanoes and volcanic eruptions
When an oceanic plate converges with a continental plate, the
denser oceanic plate subducts beneath the less dense continental plate
.
Example: Oceanic Australian Plate subducts under a section of the continental Eurasian Plate, forming the Sunda Trench and the Barisan Mountains
Oceanic Nazca plate subducts beneath continental South American Plate, forming the Andes fold mountains.
Divergent Plate Boundaries <===|===>
Oceanic-Oceanic
Fractures form at the plate boundary when 2 oceanic plates diverge
Sea-floor spreading
occurs at the zone of divergence, where magma rises from the mantle, flows out onto the sea floor, cools and solidifies
This creates a ridge of new ocean floor, called the
mid-oceanic ridge
that divides the ocean basin in half
At various points along the mid-oceanic ridge, magma builds up to form
undersea volcanoes
When the volcanoes eventually grow above sea level, they are known as
volcanic islands
Example: Mid-Atlantic Ridge in the Atlantic Ocean, between the North American Plate and the Eurasian Plate
Continental-Continental
Fractures form at the plate boundary when 2 continental plates diverge and stretch
The land in between the 2 continental plates sink, forming a linear depression known as a
rift valley
Example: East African Rift System, where the Nubian boundary of the African Plate moves away from the Somalian boundary of the African Plate
Steep Sides
Flat Lowlands
Linear Depression
Elongated