GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
Theme C: The Restless Earth Specification Content 1. Plate Tectonics Theory
2. Tectonic Activity in the British Isles
Learning Outcomes
Case studies
1.1 The structure of the earth You should be able to describe the structure of the Earth (core, mantle, crust); 1.2 How plates move … by convection currents You should be able to know that the Earth’s crust is made up of a number of plates and understand how convection currents cause plate movement; 1.3 Plate margins – processes and landforms You should be able to demonstrate knowledge and understanding of the processes and landforms associated with plate margins: – destructive plate margins: subduction zone, ocean trench; – collision zones: fold mountains; – constructive plate margins: mid-ocean ridges; – conservative plate margins: fault lines. 2.1 Tectonic features in our own back yard You should be able to identify landscape features created by tectonic activity and explain their formation – lava plateau, e.g. Antrim Plateau; – basalt columns, e.g. Giant’s Causeway; – volcanic plugs, e.g. Slemish
For 2.1, reference to places for illustration purposes only
CASE STUDY: 2.2 Earthquakes in the UK describe and explain the causes and impact of an earthquake in the British Isles using one case study
3. Earthquakes: Can They be Managed?
3.1 Earthquakes – where and how? You should be able to understand the global distribution and causes of earthquakes in relation to plate boundaries; 3.2 Physical consequences of earthquakes You should be able to know and understand that there may be physical consequences of earthquakes: – tsunami; – liquefaction;
4. Rock types and the rock cycle
Causes and impacts of an earthquake in the British Isles
3.3 Earthquakes – causes, impacts, management response You should be able to know and understand the causes and impacts of earthquakes and evaluate the management responses using two case studies (one in an MEDC and one in an LEDC): – identify the plates involved; – describe the short and long term impacts on people and the environment; – evaluate the management response to earthquakes including o prediction/precautions before the event and o immediate and long term strategies implemented after the event. You should be able to understand the formation of the basic rock types and recognise their characteristics: – igneous: basalt and granite; – sedimentary: limestone and sandstone; and – metamorphic: slate and marble.
CASE STUDIES:
Causes, impacts and management response of an earthquake in an MEDC and an LEDC
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
1. Plate Tectonics Theory Learning Outcomes – by the end of this section, you should be able to • describe the structure of the Earth (core, mantle, crust); • know that the Earth’s crust is made up of a number of plates • understand how convection currents cause plate movement; Key Terms
1.1 The structure of the earth We have a fascination with the unknown. Presents are made to be unwrapped. Boxes are made to be opened. And caves
are meant to be explored. Especially the cold, dark mysterious types. We're intrigued by the question: what's really down there?
There have been plenty of books and movies full of fanciful suggestions of strange, forgotten worlds, full of strange,
forgotten beasts...The reality is a bit more straightforward - which at least makes it easier to learn for your exam! Imagine if you were able to cut a huge big segment out of the earth (kind of like opening an orange but without all the sticky juice running over your fingers). This diagram shows you the structure of the inside of the earth that you’d reveal. Check out the video on the earth’s structure and use the box of information below to help you add annotation (fancy term for labels) to this diagram. For each layer, you’ll need to be sure to label two things (for each layer now – don’t forget!): • what it’s called • what it’s like (i.e. its characteristics)
There are two types of crust. The oceanic crust is thinner, typically 5 km to 10 km thick but is more dense and so is heavier. The continental crust is thicker, typically from 30 km to 50 km thick, but is less dense rocks than is the oceanic crust and so is lighter.
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
1.2 How plates move... How are you with mysteries…?
Have you ever sat bored in a Geography classroom, staring at one of those big world maps that Geography teachers seem to love decorating their walls with? If you have, did you notice how similar in shape Africa and South America are? It’s almost like they’d fit together like two jigsaw pieces.
You’re not the first to spot this. Alfred Wegener, a German weather man of all things, had spotted this and other pieces of strange evidence that led him to put forward what was a bit of a bizarre theory.
He suggested that the ground beneath out feet is not quite a solid and unmoving as we might think, but that it is on the move. He
got this idea from a fieldtrip to Greenland (well, somebody has to have a fieldtrip there) where he watched some icebergs drifting along in the sea. “If icebergs drift along in the sea, could continents drift along too…?” he thought to himself.
He reckoned that continents were on the move. And they had been moving for quite some time. So much so that Africa and South America were, in fact, once joined together. What now?!?
In 1858, geographer Antonio Snider-Pellegrini made these two maps showing his version of how the American and African continents may once have fit together, then later separated.
At first, he was treated like a bit of a mad man by other scientists. “The Earth moving under our feet? Continents bobbing around in the ocean? You’ve been
spending too much time stuck in an igloo in Greenland!” they mocked. Even someone called Albert Einstein was among the sceptics… The big problem was that no one could figure out any
way to explain how our massive continents could literally ‘drift’ across the surface of the planet. In fact, in one
of his more bizarre suggestions, Wegner proposed that it might be the moon that was responsible. If the moon’s
gravitational force was powerful enough to cause tides,
could it drag our continents too, he suggested? Not his best moment, really...
Alfred Wegener,jigsaw puzzle master apparently
And yet the evidence remained … was it just a coincidence that the edges of two of the great continents of the world looked like they were made to fit together…?
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
... by convection currents! Eventually, as the theory developed, scientists discovered a cause, a force powerful enough that it could shift millions of tonnes of solid rock. This discovery led to the theory of plate tectonics as it is now understood today. It states that: • The crust of the earth is not one solid whole, but is divided up into a number of sections known as _______________ • Some of these plates consist of mainly oceanic crust (e.g. _________________ ). Others have a mix of oceanic crust and continental crust (e.g. _________________ ). In fact, it’s not so much the continents that drift, but the plates which move, bringing the continents with them as they do so.
But what is the force that propels these plates? It’s the same force you unleash every time you boil a kettle of water or even just light a match - ____________________ How do convection currents actually move the plates? By three means: o friction between the convection current and the bottom of the plate o as the colder, denser plate sinks (or subducts) into the mantle, it pulls the rest of the plate along (slab pull) o as new magma seeps up into the crust, it pushes the plates apart (ridge push) Add this information into the appropriate boxes in the following diagram:
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
These massive forces of friction manage to move the crust at the staggering rate of up to (are you ready for it?) _____ per year!! Just before
you’re too under whelmed by this figure and before you boast that a granny with a zimmer frame could outrun a tectonic plate, remember the almost
unimaginable mass of rock being moved. Then think of how fast you could push your car by yourself. Not feeling so smug now, I would think. Turns out
that plate tectonics are still pretty amazing.
In fact, it’s probably just as well that the plates don’t move too quickly, otherwise walking to school might get very interesting. Come to think of it, you might never get there at all…
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
1.3 Plate margins - processes and landforms Learning Outcomes – by the end of this section, you should be able to •
show knowledge and understanding of the processes and landforms associated with following plate margins: (1) destructive plate margins and subduction zones & ocean trenches (2) collision zones and fold mountains (3) constructive plate margins and mid-ocean ridges (4) conservative plate margins and fault lines.
Key Terms
On a dinner plate, most of the interesting stuff happens in the middle. That’s were all the lovely food is – your piping hot roast
chicken and roast potatoes and roasted vegetables, all smothered in generous helping of gloopy gravy - delicious. The edges only
really feature if you manage to squelch some of your gloopy gravy over the side and onto your mum’s lovely clean table cloth while tucking into a rather uncooperative bit of broccoli. But when it comes to the earth’s plates, the edge is definitely where it’s at. If you want to see some tectonic action, that’s where
you need to head. So, what are you waiting for? Finish off your dinner (remember to eat up all your greens) and let’s visit some plate margins (fancy term for the edges of plates)! Watch the video about the Marianas Trench to find out how scientists found out about plate boundaries and what was happening at them.
A. Destructive plate boundaries Processes • Formed where plates move ________________________ • These boundaries are associated with the areas where the crust subducts down into the mantle. As the crust sinks, it slowly melts – hence the term destructive margin. Landforms There are two main features found at a constructive margin: • •
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
B. Collision zones and fold mountains Processes • Formed where plates move ________________________ • These are formed when two plates containing continental crust collide. In this case, neither is heavy enough to subduct into the mantle. Instead, the two massive continents crash into each other. Landforms As they crash into each other, they crumple upwards to form mountain ranges. The most famous of these in the Himalayan mountain range, formed as ___________ collided into ___________.
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
Constructive margins – Iceland, the land of fire… (not to be learnt in detail)
Most constructive margins are under the sea and in the middle of oceans. However, in some places, the processes and landforms emerge from the watery depths and we can get up close and personal with what’s going on. Iceland is a great example of this, lying as it does right on top of the Mid-Atlantic ridge. Although you don’t need to learn the following in detail, it will help you get a sense of what’s going on at this type of plate boundary. The plate boundary runs right through the centre of the island, quite
literally pulling it apart and creating new land in the middle. This is the
Leif the Lucky Bridge, which spans the Álfagjá rift valley (60 feet
wide and 20 feet deep) which marks the boundary of the Eurasian and North American continental tectonic plates. All the hot, rising magma brings some benefits to the people living
nearby. This is the Blue Lagoon, a hot spring, naturally warmed by the convention currents.
And this is the geothermal power station, providing electricity to the Icelandic people.
Destructive margins – Mariana Trench and the Challenger Deep (not to be learnt in detail)
The Mariana Trench (or Marianas Trench) Trench is the
deepest part of the world's oceans, and the deepest location on the surface of the Earth's crust. It has a maximum depth of about 10,924m (6.78 miles), and is located in the western North Pacific Ocean, At the bottom, the water column above exerts a
pressure over one thousand times the atmospheric
pressure at sea level. If Mount Everest, the tallest point on Earth at 8,848 metres, were set in the
Mariana Trench, there would be 2,076 meters of water left above it.
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
C. Constructive margins Processes • Formed where plates move ________________________ • These boundaries are associated with the rising section of the convection currents. As the current rises, it experiences reduction in pressure, causing melting and producing magma. This magma fills the spaces left as the plates move apart, creating new crust – hence the term constructive margin. Landforms There are two main features found at a constructive margin: • •
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
D. Conservative plate boundaries & faults Geographers are curious beasties. We notice things that others miss. We’re like those annoying friends you have who notice that your mum has given you your lunch in your old Postman Pat lunchbox because you’d left your usual lunchbox in school and it was the only other one she could find this morning (and stop complaining – if you’d only brought your lunchbox home, you wouldn’t be getting this one etc, etc... you know the drill). So let’s get those pesky powers of observation going here. What exactly are we looking at?
Processes • Formed where plates move ________________________ • At these boundaries, plates are neither created nor destroyed, hence the term ______________.
Landforms The landform found at this type of boundary is
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
Simple 2D diagram
Processes
Landforms
Explanation of name
Direction of plate movement
Destructive
Collision zone
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
Constructive
Summary of plate margins Conservative
• • •
constructive evidence = ______________________________ destructive evidence = _______________________________ collision zone evidence = ______________________________
Take this map of the world’s plate boundaries and try to identify constructive, destructive and collision zone boundaries. Highlight each one a different colour – don’t forget to complete your key! To do this, the key question to ask: what evidence will you have to look for for each type of margin?
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
In your GCSE exam, you will be asked to do more than recall knowledge. Your understanding will be tested alongside your skills of being able to apply this understanding to new situations. So, one of the skills you’ll have to work on throughout your course is the ability to use your understanding to solve problems. Let’s try it out in this exercise.
Problem solving task
Using resource materials Often, you’ll be asked to apply your understanding to previously unseen resource materials. In being assessed about a topic you have studied, you will be given resource materials (diagrams, maps, graphs, photos, extracts) that you have not specifically come across before. You will then be asked to take what you do know (what we have done in class) and apply it to what you don’t know (the new resource material). You will get lots of chances to practice this important exam skill throughout your course, starting here. Remember, like any skill, you will get better at this if you ______________ - so be prepared to make the most of chances like these during the course so that you will be best prepared for your GCSE exam. Here are some past GCSE paper questions to try this out in. 1. Study figure 1 which shows some of the plates of the earth’s surface. Answer the questions which follow.
(i) Name the type of plate boundary at A. _______________________________________________________________________________ (1) (ii) Name a landform which could be found at A and explain how it formed. ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ _______________________________________________________________________________ (3)
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
2. Study figure 2 which shows information about earthquakes in 2004 off the coast of Sumatra, Indonesia. Answer the questions which follow.
(i) Name the type of plate boundary shown in figure 2. ___________________________________________________________________________ (1) (ii) Using figure 2, name the features A, B and C at this plate boundary on the cross section diagram in figure 3 below. (3)
WE’LL COME BACK TO THIS PART OF THE QUESTION AFTER WE’VE STUDIED EARTHQUAKES (iii) Earthquakes have recently occurred at this plate boundary. Using figure 3, explain why this is so. ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ _______________________________________________________________________________ (3)
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
(i) Name the type of plate boundary at A. __________________________________________ (1) (ii) How much movement will there be along boundary A in 10 years? Circle the correct answer. 60 millimetres
60 centimetres
60 metres
(iii) Describe the distribution of earthquakes and volcanoes shown in Figure 2a. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... (iv) Why are there no volcanoes on plate boundary B? ............................................................................................................................... ............................................................................................................................... GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
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(i)
Name the type of plate boundary shown in Figure 2a. ..............................................................................................................................(1) (ii) How many volcanoes are shown on Figure 2a on the Eurasian plate? ..............................................................................................................................(1) (iii) Volcanoes are one characteristic feature of this type of plate boundary.
Describe two other features. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................ (2)
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department