1. Sunday, 30 June 2019
Enquiry Q2 – What impact does tectonic activity have on landscapes and why does this impact vary?
Learning objectives:
How does extrusive activity impact the landscapes?
Why does the activity and impact vary from place to place?
How does volcanic formation and morphology vary?
How are these differences linked to the processes at plate boundaries?
PLC: 2a, b, c, d
Key words:
Cinder volcano
Composite volcano
Shield volcano
Dike
Extrustion

2. What’s happened in the news in the last week to do with tectonics?
You should know!!!

3. Key word test Define these key terms: VEI Asthenosphere Divergent
Disaster
Convergent
Pyroclastic flow
Seismologist
Lapilli
Geotherm

4. Case study check!
Get out your case study sheets so I can look through them.
Have you been filling in your tracker?
I will ask you to make 12 case studies in total this year.
They need to be extremely detailed so you can refer back to them in the exam.
When I set homework tasks, I will ask you to use the same case study as before, but research a different aspect of it.

5. What are tectonic hazards ?
Overview of the range of tectonic events, hazards,
disasters and trends.
What is an event profile?
What is the hazard risk equation?
What are the causes of tectonic hazards?
Current theories on plate tectonics
Spatial patterns of tectonic hazards
Tectonic activity at main plate margins
Physical Impacts on landscapes
extrusive activity: volcanoes + hotspots
intrusive activity
earthquakes and tsunami
Differing landforms from extrusive and intrusive igneous activity: volcanic features +effects of earthquakes

6. ENQUIRY QUESTION 2: What are the physical effects of tectonics on the landscape?

7. What are these? Where are they? How did they get there?

8. They are part of a volcanic landscape in Cappadocia, Turkey
They are part of a volcanic landscape in Cappadocia, Turkey. The landscape was created by volcanic activity. The region is covered with deep layers of tuff (consolidated volcanic ash), basaltic lava flows and lahar deposits.
The combined effects of weathering, water and wind erosion, and the variable strength and dip of the rock layers have created highly unusual features.
Where bedding is horizontal and the rock layers relatively strong, rivers have carved steep sided valleys as at Ilhara gorge

9. Where bedding is horizontal and the rock layers relatively strong, rivers have carved steep sided valleys as at Ilhara gorge

10. The famous fairy chimneys are created by erosion processes working on layers of soft tuff covered by layers of hard rock, usually lahar deposits. The hard rock forms a protective cap, preventing the tuff layers from being eroded. The result is a mushroom shape, often with the cap layers perched precariously on top.
Eventually, when the cap is eroded away or the base of the rock pillar becomes too narrow, the chimney will collapse. *sometimes called earth pillars, or hoodoos in the USA)
People were attracted to the area because of its rich volcanic soils. They discovered that the layers of tuff could be easilyu carved into homes, stables and churches. Local people still use rooms carved out of the rock for storage, animal shelters and as part of their homes. There are several underground cities including schools, stables, churches and cooking areas, used by locals has hiding places when enemy invaders came.

11. Hoodoos in new Mexico and Banff, Canada

12. Tectonic landscapes
Tectonic processes are responsible for created incredible landscapes, which may be further modified by physical and human processes (weathering, glacial/fluvial erosion, development etc)

15. Key ideas: Extrusive igneous activity
Different types of volcanoes – formation, morphology and eruptions
Intrusive igneous activity – formations and landforms
Earthquakes and their effects on landscapes

16. Extrusion?
The upward movement of magma through the earth’s crust and onto its surface as lava. Extrusive volcanic landforms form once the lava has cooled and hardened...

17. Homework feedback!
What 3 examples did you find?

18. Extrusive Volcanic Landforms
Volcanic Cones
Fissures
Lava Plateaux

19. Volcanic Cone

20. Fissure (Laki, Iceland)

21. Fissure (Hawaii)

22. Lava Plateau (Deccan Traps, India)

23. The Deccan Plateau
700,000km2 expanse of basaltic lava covering the majority of Southern India. Formed during the later Cretaceous period, between million years ago. It may have been the result of a series of major eruptions from a hotspot that is currently under the island of Reunion in the Indian ocean
700,000km2 expanse of basaltic lava covering the majority of Southern India. Formed during the later Cretaceous period, between million years ago. It may have been the result of a series of major eruptions from a hotspot that is currently under the island of Reunion in the Indian ocean
Take google earth tour???

24. Lava Plateau (Aokigahara, Japan)

27. Volcanoes
Volcanoes are often found in chains, either because they are at plate boundaries, or because a plate is moving over a hotspot. See google earth of Mt St Helens with volcano layer showing 13 volcanoes within the cascades.
A typical cross section you may have come across at GCSE or in Science – the reality is, of course, much more complex!

28. Types of volcanoes

29. Types of Lava
Watch the clip and describe the types of lava you see. Comment on the colour, thickness and quantity! 29

30. Types of Lava
Basic or Basaltic Lava- dominated by iron manganese and is low in silica. Gas bubbles have freedom to expand as the magma rises to the surface. Eruptions are fluid and free-flowing. Constructive margins! 30

31. Types of Lava
Andesitic Lava- medium in silica content. Acid lava is medium in terms of viscosity. Temperature of eruption °C. Destructive margins. 31

32. Types of Lava
Acid or Rhyolitic Lava- rich in silica. Acid lava is so thick and viscous the gas bubbles struggle to expand. This builds up pressure to create violent eruptions. Destructive margins. 32

33. Temperature of Eruption
Types of Lava
Complete the following table to describe the chemical compositions, viscosity and temperature of each type of lava.
Basaltic Lava
Andesitic Lava
Rhyolitic Lava
Silica Content
Viscosity
Temperature of Eruption
The thicker the lava, the more violent the eruption…give reasons for this general rule! 33

34. Temperature of Eruption
Types of Lava
Complete the following table to describe the chemical compositions, viscosity and temperature of each type of lava.
Basaltic Lava
Andesitic Lava
Rhyolitic Lava
Silica Content
Medium
Viscosity
Low (runny)
High (thick)
Temperature of Eruption °C
Less that 750°C
The thicker the lava, the more violent the eruption…give reasons for this general rule! 34

35. Temperature of Eruption
Types of Lava
Complete the following table to describe the chemical compositions, viscosity and temperature of each type of lava.
Basaltic Lava
Andesitic Lava
Rhyolitic Lava
Silica Content
Low
Medium
High
Viscosity
Low (runny)
High (thick)
Temperature of Eruption °C °C
Less that 750°C
The thicker the lava, the more violent the eruption…give reasons for this general rule! 35

36. Decipher the types of lava and justify your answer!B

37. Decipher the types of lava and justify your answer!
Basic/Basaltic
Low Silica
Low Viscosity
High Temperatures A

38. Decipher the types of lava and justify your answer!
Acid/ Rhyolitic
High Silica
High Viscosity
Low temperature B

39. Extrusive Features in action!
Remember, these are the result magma rising to the surface and erupting as lava. The features are dependent upon the types of lava and whether the extrusion is gaseous, solid or liquid.
Aa forms when lava flows rapidly. Under these circumstances, there is rapid heat loss and a resulting increase in viscosity. When the solid surface crust is torn by differential flow, the underlying lava is unable to move sufficiently rapidly to heal the tear. Bits of the crust are then tumbled in and coated by still liquid lava, forming the chunks.
Pahoehoe forms when lava flows more slowly. Under these circumstances, a well-developed skin can form which inhibits heat loss. 39

40. Fissures and Vents
Lava can erupt from long cracks called fissures or localised vents. The resultant landforms created are greatly determined by the nature of the opening from which the magma emerged to form lava.
Fissure eruptions- basic lava creates extensive lava plateaus. Hollow areas of the landscape are filled to create flat, featureless basalt plans.
Vent eruptions- usually create cone shaped landforms such as the iconic volcano images complete with a summit crater. 40

41. Types of volcano The type of volcano will be affected by:
The type of lava erupted
The nature of the eruption
The type of plate margin
The type of volcano produced by eruptions depends on the type of lava erupted and the nature of the eruptions themselves. These in turn are greatly influenced by the type of plate margin on which they are formed

42. Magma type & volcano morphology
Basaltic – huge, low relief shield volcanoes plus small scoria cones and fissure vents.
Andesitic – steep sided strato-volcanoes; layers of lava, ash and tephra.
Rhyolitic – central craters with lava plugs / domes, due to high viscosity of the lava.

43. Types of volcano Divergent margins
Fissure eruptions and shield volcanoes
Low, gently sloping sides, wide base
Basaltic lava, low viscosity, high temp so covers long distances before it cools and solidifies
Frequent, low magnitude eruptions
Also found at hotspots
Convergent margins
Cone shaped
Less frequent, more explosive eruptions
More silica and cooler, so more viscous
Flows slowly, cools quickly creating cone shape with narrow base and greater height
Often composite with alternating layers of ash and lava
1. Divergent margins
2. Tend to give rise to fissure eruptions and shield volcanoes.
Fissure eruptions occur along fractures and fault lines, while shield volcanoes erupt from a vent.
3. Shield volcanoes are typically low in height with long, gently sloping sides and a wide base.
4. The lava that erupts from them is basaltic, which means it has a low viscosity due to its low silica content. Being quite fluid and hot (about 1200 C, the lava flows quickly and covers long distances before it cool and solidifies, which explains the shape of the cone.
5. Eruptions are frequent but low in magnitude – magma is able to reach the surface relatively easily since the plates are diverging and the crust is fracturing. This means that there is seldom a real build – up pf pressure.
6. Such volcanoes also occur at hotspots
7. At convergent margins
8. Eruptions tend to be less frequent and much more explosive. Rising magma often has a much greater thickness of crust through which to pass, and fractures providing easy routeways tend to be less common.
8. The lava has more than 50% silica. This, along with lower temps of about 800 C make it much thinker and vidcous so it flows slowly and cools quickly, giving rise to a cone with a narrow base and a greater height.
9. They are often composite in structure, with alternating layers of ash and lava. The ash is produced by a highly explosive eruption, often after blocking of the vent, fragmenting parts of the cone or the plug of solidified magma.
Watch video

44. Hawaii – shield volcanoes
Volcanoes formed by tectonic plate moving north west over hotspot
Oceanic hotspot location
Gently sloping sides
Oceanic hotspot location
Gently sloping sides due to “runny” lava comes directly from the asthenosphere (over 1000C) and can travel up to 60 km/hr, sometimes reaching the sea
As the plate has moved north west, the volcanoes have been carried away from the hotspot in a northwest direction creating a chain of volcanic islands and extinct submarine volcanoes
A new volcano is erupting 35 km south-east fo hawaii. Loihi is only 3,000 m tall and 2000m below sea level but is expected to reach the surface in 10,000 to 100,000 years.
New volcano, 3000m tall and 2000m below sea

45. Soufriere Hills, Montserrat – Composite volcano
Ash eruptions, pyroclastics flows, mudslides and lava flows have built up a composite volcano

47. Volcano type Diagram Key features Explanation Example Fissure Shield
Dome
Cinder
Composite
Caldera
Laki (iceland) - fissure
Kiluaea – Shield volcano
Montserrat – composite volcano
Yellowstone – caldera
In your explanation, try to include information on what type of eruption caused the volcano
Wherever possible, try to use examples we have already used e.g. Kiluaea, Montserrat, Yellowstone

48. Teaching time!
You have 4 minutes to read over your type of volcanic eruption.
You will then be teaching each other your type.
You need to include:
What type of magma it is
A general description of how it erupts
An example of this type of eruption
Any extra things of interest

49. Types of eruption Hawaiian – calm, non explosive
Vulcanian – explosive, short lived
What type of eruption is associated with your case studies? Why? What impact has this had? Add this to the explanation column on your table
There are other types, students should research the main types, with reference to their case studies

50. Next lesson ….
Intrusive igneous landforms

51. Reflection time
Fill in your PLC for 2a, b, c – d is your homework so this need to be filled in before next lesson.

52. Homework set 30/09 DUE 6/10
Research the theory of hotspots made by J. Tuzo Wilson. Was the theory accepted at the time? Has it stood the test of time? What examples do we have of this theory now?
Complete the sheet about volcano types given in the lesson and refer to your case studies in it. Make sure the example refers to the type of plate boundary it is on.
Pick two tectonic activities (case studies) and research the type of landforms they produce (try and use case studies that you have already looked at). Make a presentation to give next lesson! (5 minutes each).
Where is it?
What landforms are there now?
How were they formed?
What specific feature of the tectonic activity caused it to form these specific landforms? (eg. type of volcano/plate boundary)
Any other information that is relevant