1. TOPIC 1:TECTONIC PROCESSES AND HAZARDS
(Lesson 6)

2. 1. Why are some locations more at risk from tectonic hazards?
ENQUIRY QUESTION 1:
1. Why are some locations more at risk from tectonic hazards?

3. Previous Lesson Objectives:
To consider further developmental theories regarding plate tectonics
3.The Discovery of the Mid Atlantic Ridge (MAR)
4. Palaeomagnetism and sea floor spreading
5. Subduction and ocean trenches

4. Specification content
1.1 The global distribution of tectonic hazards can be explained by plate boundary and other tectonic processes
1.2 There are theoretical frameworks that attempt to explain plate movements

5. Today’s lesson Objectives
To have a good spatial understanding of the distribution of plate boundaries resulting from divergent, convergent and conservative plate movements by looking at global maps
To have detailed understanding of processes occurring at constructive plate boundaries
(REF: Edexcel A Level Book 1Hodder p2-5
Geography for Edexcel A Level Year 1 Oxford p9-11)

6. World Map showing plate boundary types Q: What do you think the black arrows indicate?

7. What is a plate boundary?
When 2 tectonic plates meet they form a PLATE BOUNDARY.
Each type creates distinct processes and landforms.
It is at these plate boundaries that MOST tectonic activity takes place ( mountain building, volcanoes, earthquakes..)

8. Three main types of plate boundary:
Convergent/
Destructive
Divergent/
Constructive
Transform/
Slipping/
Conservative/
Passive
Firstly, there are three types of plate boundary, each related to the movement seen along the boundary.
Divergent boundaries are where plates move away from each other
Convergent boundaries are where the plates move towards each other
Transform boundaries are where the plates slide past each other.
Presenter: See diagrams for each - it is important to remember the names of the boundary types and the motion involved.

9. What are the names of the following plate boundary types:
Where two plates move apart from one another?
Divergent/constructive
Where two plates move towards one another and meet?
Convergent/destructive
Where two plates move past each other either in the same or different directions?
Conservative/transform/slipping/transform

10. A fourth plate boundary…
COLLISION PLATE BOUNDARY
Where 2 continental plates move together
Collision

11. Constructive Destructive Conservative Collision
Where an oceanic and continental or oceanic/oceanic plate converge (meet)
Where two plates (oceanic or continental) diverge (move apart)
Conservative
Collision
When two plates move past each other in different directions or at different rates
Where two continental plates converge (meet)

12. Kung Fu Panda! (click below)

13. Dynamic plates

14. Pacific Ring of Fire Volcanism is mostly focused at plate margins…
This map shows the margins of the Pacific tectonic plate and surrounding region. The red dots show the location of active volcanism. Notice how the majority of the volcanism is focused in lines along the plate boundaries? For this region this area is known as the “Pacific Ring of Fire”.
But why are all of the volcanoes located at the plate margins?
Volcanism is mostly focused at plate margins…

15. As with volcanoes, earthquakes are not randomly distributed over the globe
At plate boundaries, friction causes them to stick together. When built up energy causes them to break, earthquakes occur ( N.B. but some are also found intra plate…)
Figure showing the distribution of earthquakes around the globe
The black dots on this map of the world depict where earthquake activity is occurring. You can see that, as with volcanoes, the earthquakes are NOT randomly distributed around the globe. Instead they occur in linear patterns associated with plate boundaries.
(Note this diagram of earthquake distribution closely resembles the Pacific Ring of Fire distribution of volcanism).

16. Pacific Ring of Fire movie ( click below )

17. The Tectonic Processes which occur at Constructive/divergent plate margins

18. Constructive/Divergent plate boundaries(see p.23)
What happens at a constructive plate margin?
Here, tectonic plates are moving AWAY from each other.
Convection currents in the asthenosphere( or by ‘ridge push’ ) rise to create doming in the lithosphere and tensional forces that pull the plates apart.
New crust is created by up- welling basaltic lava producing some of the youngest parts of the earth’s surface( see earlier notes on sea floor spreading..)
( watch secs to 5.40 secs)

19. 1.Constructive/Divergent
Plates move apart, usually under the ocean
Cracks and fractures form where there’s no solid crust.
Magma forces its way up to the surface to form a VOLCANO( often submarine)
Shallow focus Earthquakes also occur.
Transform faults also often form
Example: The Mid Atlantic Ridge

20. Age of Oceanic Crust Courtesy of www.ngdc.noaa.gov
Ocean Ridges: This map shows the age of the oceanic crust. The red colouring shows the youngest ages, whilst the dark blue shows the oldest ages (around 200 million years old).
Presenter ask: Where are the Ocean Ridges located? I.e. where are the divergent boundaries?
Answer: The divergent boundaries are where the plates are pulling apart and new material is being produced. Therefore the Ocean ridges are in the middle of the red areas (the boundaries are in fact shown on the map). We can see a progression of the oceanic crust getting older away from the ocean ridges (like a conveyer belt).
Presenter: Before moving on to the next slide, point out Iceland. The divergent boundary runs straight through Iceland….
Courtesy of