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Brendan Kennelly for Leaving Cert English: Begin

"Begin" by Brendan KennellyYou may also like: 2019 Guide to Leaving Cert English. Full notes on Brendan Kennelly will be made available to everyone who has the 2019 guide, free of charge, as soon as they are ready.

Summary: a philosophical reflection on starting something new again and again communicated through the description of a morning walk across the Grand Canal in Dublin.

Style features:
anaphora (1) (highlighted in bold) adds a sense of determination as does the repetition of the word “begin” throughout the poemenjambment highlights the never ending need to begin again imperative tone, “begin again” is an encouraging command to never give up alliteration e.g. “dying in dark / determination” enhances the imageryreference to familiar places, “Pembroke Road” near the Aviva Stadium in Dublin 4, make the poem more accessibleimagery appeals to multiple senses: “summoning birds”, “sight of the light”, “roar of morning traffic”, “crying birds in the sudden rain”, “branches…

Plate Tectonics for Leaving Cert Georgaphy

This is a chapter from our Geography Notes. Coming soon! In the meantime, here are the full sets of notes we have in store. 

Tips

Plate tectonics is the basis for much of what is to come in the physical geography section of the course, so it is important that you have a firm grasp of this chapter. There will always be short questions on the very basics of plate tectonics, so learn the basic stuff well and you’ll be guaranteed some marks.

My approach to geography was always to write out a list of keywords and definitions at the start of the chapter, and try to incorporate as many of these into your answers as possible. This is useful as, naturally, the key definitions will be easily transferable from one answer to another, so this cuts down the amount of learning you’ll have to do.

Another piece of advice I would have about this chapter is know and understand your diagrams very well. If you can imagine what subduction for example would look like if you could see it happening then it will be much easier to write an answer about it.

Keywords 

Crust: thin outer shell of the earth. Made up of solid rock that is called the lithosphere. The crust can be divided into continental crust and oceanic crust. 

Mantle: lies between the crust and the core of the earth. Very hot, but most remains in solid form. 

Outer core: made up of hot, molten rock. 

Inner core: up to 5000 degrees Celsius. Under so much pressure that it remains solid rather than molten. 

Oceanic crust: lies underneath oceans. As thin as 5km thick at parts (v thin). Made up of very old rocks eg Basalt. 

Continental crust: main land masses situated on this crust. V thick- can be up to 60k thick. Consists of younger rocks eg Granite 

Lithosphere: rocky outer part of the earth. Made up of the brittle crust and top part of the upper mantle. Coolest and most rigid part of the earth. 

Asthenosphere: the denser, weaker layer beneath lithosphere. Lies between 100km and 410km beneath Earth’s surface. Temperature and pressure so great that rocks soften and become partly molten. 

Plates: each of the several rigid pieces of the earth’s lithosphere which together make up the earth’s surface. 

Semi-molten magma: mixture of melted and half-melted rock found beneath the earth’s surface. 

Thermal convection currents: the movement of magma in the mantle caused by the heat coming from the core. Causes plates to move. 

Destructive boundary: a boundary where plates collide. It is called such because land is being destroyed. Causes features such as earthquakes and fold mountains. Eg Nazca Plate and South American Plate. Also known as convergent boundaries. 

Constructive boundary: a boundary where plates separate. Called such because land is being created. Causes features such as volcanoes. Eg Eurasian Plate and North American Plate. Also known as divergent boundaries. 

Conservative boundary: a boundary where two plates slide past each other. Crust is neither created nor destroyed. Also known as passive/transverse/neutral/transform boundaries. Eg North American Plate and Pacific Plate. 

Continental Plates: Earth’s major plates on which the continents are situated. 

Plate Boundaries


***KEY DIAGRAM*** Study and memorise this diagram very well. Questions examining it come up very often in short questions, and it is useful to know when you are providing examples in long questions.



The red lines are plate boundaries. The arrows indicate the direction in which the plates are moving. Where two arrows point away from each other, there is a divergent boundary. Where two arrows point toward each other there is a convergent boundary.


Types of Plate Boundary:


Conservative plate boundary 


Convergent plate boundary


Divergent plate boundary


Q: Examine- with the aid of a labelled diagram- the process of global crustal plate movement as it is currently understood. (30 marks)

Tips: Before jumping into any question, be sure to underline the keywords. It’s easy to miss the finer details of a question while under exam pressure. Here, I would underline ‘labelled diagram’ and ‘global crustal plate movement’. 

Also note that it is worth thirty marks. As each SRP (standard relevant point is worth two marks, you will need fifteen SRPs. Your diagram will make up some of these marks, too.

Answer: 

The earth’s core is extremely hot- almost 5000 degrees Celsius. The mantle is made up of semi-molten magma, so it can flow. When the magma nearest the core is heated, it rises slowly toward the earth’s crust (or the lithosphere), as this part is less dense than the cooler parts that are further away from the core. 

As the rising magma reaches the earth’s crust, it is forces to spread laterally. As this happens, it can cause plate boundaries to collide or separate. When the plates separate, it’s called a divergent boundary. At divergent boundaries, land is created. Often magma escapes through the fault in the crust and forms a volcano eg in the Mid-Atlantic Ridge. A mid-ocean ridge forms when a line of volcanoes form under the sea. After magma hits the air or seawater having escaped through the fault, it cools and hardens.

When plates collide, it’s called a convergent or destructive boundary. Land is destroyed at this type of boundary. What can occur here are fold mountains, where the plates under the pressure eg Rocky Mountains at the North American Plate and Pacific Plate Boundary. Volcanoes can also be formed here as a result of subduction. Subduction happens when the heavier plate in a convergent boundary goes under the lighter one, and melts and turns to magma eg Mt. St. Helen’s at the North American Plate and Pacific Plate boundary.

When plates slide past each other it can be called a passive/ conservative/ neutral/ transform/ transverse boundary. Land is neither created nor destroyed at these boundaries. Eg Pacific Plate and North American Plate.

This can all happen as the plates are all separate rigid sections of the earth’s crust, which are divided by fault lines and are floating on the mantle’s magma, and, therefore, are capable of movement.

Temperatures in the lithosphere are cooler, so the laterally moving magma cools, becomes more dense, and sinks back down toward the core. It eventually returns to its original position, and, in this way, the circular convection current of magma is completed.

Theory of Continental Drift and the Theory of Sea-Floor Spreading

Keywords 

Alfred Wegener 
1912 
Pangaea 
Supercontinent 
Laurasia- N. America, Europe, Asia, 
Gondwanaland- S. America, Australia, India, Antarctica, Africa 
Tethys Sea 
200 MYA (million years ago) 
50 million years from now 
Africa breaking apart. 
2cm per year 

Tip: use these keywords as a basis for every answer you write on this topic. Try to get at least one SRP out of each keyword.

Proofs 

Continental fit: Africa and South America’s coastlines have shapes that would fit into one another like a jigsaw. People tried to say this proof was irrelevant as erosion would’ve changed the coastlines, but it is proven to be true as their underwater coastlines (which are not subject to erosion) match, too. 
Matching mountain ranges: Appalachian Mts, Donegal Mts, Scottish Highlands- all run North East to South West 
Matching fossils: certain types of ferns and lizards can be found in both Africa and South America- must have been a land border at one point. 
Matching glacial deposits 
Same rock types despite being miles apart 

Q: Write a note on the Theory of Continental Drift (30 marks)

In 1912, a man called Alfred Wegener first proposed the theory of continental drift which we accept today as being true.

Approximately 200 MYA (million years ago), there was only one continent on earth; a supercontinent called Pangaea. As the tectonic plates are constantly moving, about 60 MYA, the continent had shifted dramatically. There were now four large land masses, and they were given two names. The largest land mass was now a continent called Laurasia, which contained today’s continents of Europe, North America, and Asia. The other three were called Gondwanaland, and this contained South America, Africa, India, Australia and Antarctica. Gondwanaland and Laurasia were separated by the Tethys Sea. The land masses then began to separate at a rate of 2cm per year. By 65MYA, the land masses had separated to become the continents we know today: Europe, Asia, Africa, Antarctica, North America, South America, and Australia.

This theory was proved by a number of factors. One was the fact that S. America and Africa’s coastlines looked as though one would slot into the other, despite the fact that they are separated by an entire ocean. This is called the theory of continental fit. People at the time discredited this theory by saying the coastlines would’ve eroded, and there was no way they’d still look the same millions of years later. They investigated underwater coastlines, which wouldn’t have been subject to erosion, and found that these coastlines matched too, proving the continental fit theory. Wegener also discovered matches between rocks and rare fossils in Brazil and South Africa. There are matching mountain ranges in very different parts of the world, for example the Appalachian Mountains in North America, the Donegal Mountains in Ireland, the Scottish Highlands, and also in Norway and Sweden. These mountains all run North East to South West. This meant that they were all formed at a time when the Eurasian and North American plates collided. They are fold mountains. There are also matching glacial deposits in Australia, Antarctica, India, Africa and South America.

Continental drift never stops because there are constantly thermal convection currents in the earth’s mantle with semi-molten magma moving the plates. 50 million years from now, the earth will look completely different. Africa will probably even be divided into two separate parts.

Theory of Sea Floor Spreading

Keywords 

Rock in the centre of Atlantic sea floor- 2 million years old 
Rock at the edge- 200 million years old 
Atlantic Ocean getting bigger 
Mid Ocean Ridge- Mid Atlantic Ridge 
Harry Hess 
1963 
2.5cm per year 
North American and Eurasian Plate 
South American and African Plate 
Divergent plate boundary 
Constructive movement 
Iceland/ the Azores 

Elaborated:

When the theory of continental drift was being investigated, researchers went underwater and tested the rocks there. They discovered that the rock nearest the Mid-Atlantic Ridge in the middle of the Atlantic Ocean was about 2 million years old, and that the further away the rock was from the ridge, the older it was. This shows that magma was coming out of the ridge, cooling, and forming land. Some of the furthest rock on the sea floor from the ridge was about 200 million years old, which is around how long ago Pangaea began to separate. This was all discovered by Harry Hess in 1963.

The North American plate and the Eurasian plate continue to move away from each other at a rate of 2.5cm per year. The South American and African plates are also separating from each other, and also causing the Atlantic Ocean to get bigger These boundaries are divergent/constructive, which is what caused the Mid-Atlantic Ridge. The Mid-Atlantic Ridge is effectively just an underwater volcanic mountain range. It runs from North to South.

When the magma hardens under the water and forms a particularly high peak, the land comes above the water and forms islands. Two examples of this are the Azores and Iceland.

Tip: There isn’t a whole lot of information on this particular title, so make sure to know what we do have well and use up all of your keywords in an answer. Being specific will win you marks in any question you do, so try to remember dates (in this case, the year Harry Hess discovered this concept: 1963), and definite examples (the Azores and Iceland).

Types of Plate Movements/Boundaries 


Divergent/Constructive 

Oceanic Divergence features: Mid-Ocean Ridges eg Mid-Atlantic Ridge 
Volcanoes 
Continental Divergence features: Rift Valleys eg African Rift Valley 

Convergent/Destructive 

Oceanic-oceanic convergence features: island arc, ocean trench 
Oceanic-Continental convergence features: volcanic mountains eg the Andes 
Continental-continental convergence features: fold mountains eg the Himalayas 
(Earthquakes are common to all types of convergent boundaries) 

Conservative 

Earthquakes 
Rift valleys 

Q: Explain with the aid of a labelled diagram how one feature of oceanic divergence is formed. (30 marks)


Tip: Before starting this question, as always, underline your key words. For me here they would be diagram, one, oceanic divergence, formed. Remember that you will lose marks if you do not include a diagram. It doesn’t have to be good, it just has to be clear about what’s happening.


Answer: One feature of oceanic divergence is a Mid-Ocean Ridge. An example of this is the Mid-Atlantic Ridge, which was first discovered in 1948. Mid-Ocean ridges from when two underwater plates separate from one another. In the case of the Mid-Atlantic Ridge, the Eurasian Plate and the North American plate are separating. This is a constructive boundary, as new land is being formed. 

In the earth’s mantle, there are thermal convection currents of magma. This causes the plates to pull apart from each other. The plates are rigid sections on the earth’s lithosphere, which are floating on the mantle’s magma. 

Magma emerges through the crack that has been formed. It meets the cold water, hardens quickly and creates new oceanic crust. The rock that is formed is basalt. This continues to occur as the plates move apart at a rate of 2.5cm per year.

The magma builds up and forms a mid-ocean ridge. The theory of sea-floor spreading reinforces this theory. The rock near the middle of the ocean floor is just 2 million years old whereas the oldest is about 200 million years old. Though the ocean is getting bigger, Earth is not, so land is being destroyed during subduction in other places. 

Most of the ridge remains below sea level, but in some cases it rises so high that it forms an island above the water. Some magma emerges more violently in individual pipes to form hundreds of volcanic mountains.

Q: Explain with the aid of a labelled diagram how one feature of continental divergence is formed (30 marks)

When two plates of the earth’s crust separate from one another, it is called a divergent plate boundary. An example of two such plates is the Arabian plate and the African plate. About 400 million years ago, the Eurasian and African plates collided, which weakened the crust and caused the fissure. At this fissure, a rift valley, called the African Rift Valley has formed. This rift valley is over 4800km long. Huge pressure built up in the molten magma and magma rises up to cause a dome in the earth’s crust. This causes huge parallel faults to occur. The African Rift Valley formed when land between the faults slipped downward as tension pulled the plates apart.


The separation is ongoing. As he earths lithosphere is divided into rigid sections called plates which are floating on the magma and being moved by convection currents, they move apart from each other at a rate of about 2.5cm per year. Already the rift is filling up with water and creating lakes such as Lake Tanganika and Lake Milawe. This is also how the Red Sea separating the Arabian and African plates, and also the Gulf of Aden were formed.

As they continue to separate, in about 50 million years, Tanzania, Kenya and Somalia will have split from the rest of Africa as the gulf will have filled completely with water. 

Q: Plate boundaries are zones where crust is both created and destroyed. (30 marks)


The earth’s lithosphere is divided into rigid sections which we call plates. All of the plates are floating on semi-molten magma which is about 1000 degrees Celsius in the earth’s mantle. The earth’s core is about 5000 degrees Celsius. The magma nearest the core heats and becomes less dense. It floats to the top, spreads laterally when it hits the crust, cools, condenses, and sinks back to its original position, which completes a cycle called a thermal convection current.

The plates are separated by cracks or fissures. The thermal convection currents cause the plates to move. A number of things can happen at the boundaries of these plates. If two plates are moving toward each other, they are said to be convergent, also known as a destructive boundary. Here, land is destroyed eg the Indo-Australian and Eurasian plates boundary. Here, a huge amount of pressure caused the plates to buckle and form a fold mountain range called the Himalayas. What can also occur at convergent plate boundaries is subduction. This happens when one of the two plates that are converging is heavier than the other, so the heavier ne ‘subducts’ or sinks under the lighter one and melts, causing huge volumes of magma which rises up through the fissure and creates a volcano eg Mt Vesuvius at the African and Eurasian plates boundary. 

When two plates are moving away from one another, they are said to be divergent or constructive, as land is being created. What can occur here are volcanic mountain ranges, such as the Mid-Atlantic Ridge at the Eurasian and North American plates boundary. The plates separate, widening the fissure and allowing magma to come to the earth’s surface, which then cools and hardens. In the underwater instances of this, sometimes so much lava cools that it creates a mound and rises above the water, forming an island arc eg Japan at the Pacific and Eurasian plates boundary.

Here is some analysis of the 2017 paper from The Independent

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