Tectonic hazards Gateway 1

Question 1

Why do tectonic plates move?

Answer 1

1. Convection currents are movements of heat within the mantle. Material in the mantle is heated by the core, causing the mantle material to expand, rise and spread beneath the plates.
2. This causes plates to be dragged along and to move away from one another.
3. Then, the hot mantle material cools slightly and sinks, pulling the plates along.
4. The sinking mantle material gains heat again as it nears the core and the whole process repeats.
5. Slab-pull force is when the dense, sinking oceanic plate at subduction zones pulls the rest of the plate behind it. ( Main driving mechanism for plate movement)
6. The subducting or sinking plate drives the downward moving portion of convection currents.
7. Mantle material found away from subducting plates drives the rising portion of convectional currents.

Question 2

What are different types of plate boundary?

Answer 2

• Divergent (Plates moving away
  from one another)

-Convergent (Plates moving towards one another)

-Transform (Plates moving past one another)

Question 3

Types of Diverging plate boundaries?

Answer 3

• Oceanic-Oceanic plate divergence
• Continental-Continental plate divergence

Question 4

How are landforms formed at Oceanic-Oceanic plate divergence?

Answer 4

When two oceanic plates diverge, fractures are formed at the plate boundary → magma rises at the zone of divergence to create a edge of new ocean floor known as the mid oceanic ridge → at various points of mid Atlantic ridge magma builds upand solidifies to form undersea volcanoes → when these volcanoes grow above sea level, they are known as volcanic islands.

EX: Mid-Atlantic Ridge in the middle of Atlantic ocean, formed when North American and Eurasian plate moved away from one another.

Question 5

How are landforms formed at continental-continental plate divergence?

Answer 5

When two continental plates diverge, they are stretched causing fractures to form at the plate boundary → the land in between the two continental plates sink forming a linear depression known as a rift valley

EX: East African rift system involves the Nubian and Somalian plate

Question 6

Types of Converging plate boundaries?

Answer 6

-Oceanic-Oceanic plate convergence

-Continental-Continental plate convergence

-Oceanic-Continental plate convergence

Question 7

How are landforms formed at Oceanic-Oceanic plate convergence?

Answer 7

When two Oceanic plates diverge → denser Oceanic plate subducts beneath the less dense Oceanic plate. → The area where this occurs is called the subduction zone. →At the zone, a depression is formed, which is the Oceanic trench.→
At the same time, the denser subducting plate causes mantle material above it to melt, forming magma which rises to the crust to form volcanoes.

EX: Convergence of Pacific plate and Philippine plate, forming Mariana Trench & Mariana Islands

Question 8

Internal structure of the earth

Answer 8

Core → radius of about 3500 km → composed of mostly iron and nickel → solid inner core of about 1400 km thick →liquid outer core of about 2100 km thick →3000°C to 5000°C

Mantle →2900 km thick → 800°C to 3000°C

Crust
a few kilometres to more than 70 km thick → less than 1% of earth’s volume

Question 9

Oceanic-oceanic plate convergence

Answer 9

When two oceanic plates converge and collide, the denser oceanic plate will subduct beneath the less dense oceanic plate → a deep oceanic trench is formed at the point of subduction → the subducted oceanic plate causes the mantle material above it to melt, forming magma → the magma rises through the crust and forms volcanoes. eventually a chain or arc of islands is formed → earthquakes may also occur at the boundary between two plates. this is due to the friction created between the moving rock masses when a plate subducts under another

Ex- Philippine plate and pacific plate → mariana trench and mariana islands

Question 10

continental-continental plate convergence

Answer 10

When two continental plates converge and collide, the crusts are compressed and causes massive folding → the crust of the continental plate buckles and folds→ the folding of the crusts forms a range of fold mountains

Ex- Indian plate & Eurasian plate → himalayas

Question 11

oceanic- continental plate convergence

Answer 11

When an oceanic plate converges with a continental plate, the denser oceanic plate subducts beneath the less dense continental plate → an oceanic trench is formed at the point of subduction → the continental plate buckles and folds forming fold mountains

euraisian plate annd australian plate → sunda trench and barisan mountains

Question 12

oceanic- continental plate convergence

Answer 12

When an oceanic plate converges with a continental plate, the denser oceanic plate subducts beneath the less dense continental plate → an oceanic trench is formed at the point of subduction → the continental plate buckles and folds forming fold mountains → at the subduction zone, the sinking plate causes the mantle material above it to melt, forming magma → magma rises through the crust giving rise to volcanoes and eruptions

Ex- Australian plate and Eurasian plate → barisan mountains and sunda trench

Question 13

Transform plate boundaries

Answer 13

Plates slide past each other forming a transform fault → in the process tremendous stress builds up and is eventually released → often in the form of violent earthquakes