Year 13

YEAR 13 – JUNE 2009 – REVISION

I’m getting lots of emails etc. at the moment asking questions etc.. which is great – you are clearly working very hard. It makes sense for me to also post answers to emails here so that you can see if any of the questions are asked are ones you wanted to ask and what the answers were – I will add answers / questions as they come through:

1. What to put in if an essay talks about spatial and temporal variations in mass balance:
  
Ok – obviously the first part of this essay you will be making it clear what mass balance is – show understanding of a glacier system – inputs, stores/transfers and outputs (and examples) – could also mention the diagensis process (snow-ice) – and the key terms accumulation / ablation
 
1. Spatial – differences in mass balance – temperate / polar
Alpine glaciers (e.g. Glacier de Bon Pierre – Alps) – precipitation over 2000mm – greater input – and higher temps in summer – so mass balance fluctuate more widely compared to high latitude area – e.g. Alaska – much lower preciptiation and less melting so less fluctuations in mass balance (more of an equilibrium) – but even variations between temperate glaciers. Here are some figures for you to make some comparisons about spatial differences linked into retreat – between temperate glaciers
Rates of glacial retreat:
Norway – 1850 – 1988 (28.7 m yr-1)
Alps – 1894 – 1980 (15.6 m yr-1)
Rockies – 1890 – 1974 (15.2m yr-1)
New Zealand – 1894 – 1990 (25.9m yr-1)
 
2. Temporal
(i) Diurnal – flucutations day / night
(ii) Seasonal –  talk about seasonal variations – winter v/ summer – there is the net budget over a year diagram that could also be put in and explained
(ii) Annual – link to climate change – nice bit here linked to Athabasca and its retreat over recent times – it has been in retreat for over 200 years (so started retreat before industrialisation & associated inc. in GHG) BUT – nevertheless – http://earthobservatory.nasa.gov/IOTD/view.php?id=7679 “In the past 125 years, the Athabasca Glacier has lost half of its volume and receded more than 1.5 kilometers (0.93 miles) “- another useful quote from this website – ” Since 1960, glaciers around the world have lost an estimated 8,000 cubic kilometers (1,900 cubic miles) of ice. That is approximately enough ice to cover a two-kilometer-wide (1.2 mile-wide) swath of land between New York and Los Angeles with an ice sheet that is one kilometer (0.62 miles) tall.”
 
Could also bring in the 1750-1850 mini-ice age in Europe – so would have been more positive mass balance (even the River Thames froze – had frost fairs) – alpine glaciers advanced down into main valleys.
 
Can in the conclusion do the recognition bit that even if negative mass balance and glacier in retreat – glacier may move forward under gravity – so can appear that a retreating glacier is advancing.
 
Some essays will have less to write than others – but remember to make sure you have talked about all the theory associated with the focus of the essay – e.g. in this case mass balance, accumulation, ablation, equilbirium, net-budget, glacial systems (inputs, stores, outputs etc.) etc…
 
2. What do I need to write about the influence of climate , soil/topography and humans on distribution, structure and functioning?
 Regarding ecosystems – I would structure the essay according to the distribution, structure and functioning – and then talk about the relevant factors affecting them, rather than the other way round – particularly if find less to talk about on terrestrial factors (rather than writing it according to atmospheric, terrestrial and human – and then applying these to distribution, structure and functioning does that make sense)?
 
Distribution is simply the location / how spread out – so can look at atmospheric conditions, as well as soil – although of course the soil is also affected by the climate anyway – with human activity – if for example Trop Rainforest – you can talk about deforestation – impact on distribution – learn some figures – maybe deforestation rates / amount loss to be able to illustrate this. For Temperate grasslands – could look at desertification caused by extensive agriculture etc.
 
Structure – is really the physical structure – biomass- including vegetation and animals – could talk about the layering for example in the Tropical Rainforests and the reason for this – the diversity of the vegetation and the fact that therefore vast amount of ecological niches and then link this to the diversity of the animals. Also how climate has affected structure – with some of the adaptations in the Trop Rainforests, the Buttress Roots, the fact that because the soil is relatively infertile – most of nutrients near surface due to recent leaf fall / rapid decomposition – lots of the roots are close to the surface. Again human activity in Trop rainforest – opening up the rainforest – impact on diversity of vegetation, removal, destruction of the 4 layered system. Shifting cultivation – opening up small areas – creates more light – impact of this etc. -in turn because shifting cultivation smaller scale – may lead to some secondary succession.
 
Functioning – loads to talk about – this relates to
(i) Nutrient Cycling – look at Gerhsmls model – climate – rapid decomposition etc… – so explain little litter store etc…. ; soil heavily weathered – again relatively small store – large amount in biomass – how does human activity then affect the nutrient cycle following deforestation – so think about the disrupted nutrient cycle (remmeber you have a labelled diagram of this) – lack of interception, removal of nutrients by surface runoff etc. etc.
(ii) Functioning – energy flows / productivity – so GPP / NPP / linked into high biomass which might have mentioned in structure – but lots to talk about with the climate here on the NPP/GPP – human impact – if removing vegetation?
 
 
Does that help??
 
3. What are Temporal Variations and changes in an ecosystem?
 
(i) could be natural changes in an ecosystem – succession occuring over time; some sort of disturbance resulting in a sub-climax (e.g. some arresting factor); or a large scale disturbance – causing secondary succession, or creating area of new land-surface (e.g. Krakatoa -part of island destroyed – new succession on the new area
(ii) could be human induced – plagio-climax – heather moorlands – but if human activity were to stop what would happen??? could again be deforestation (large scale) or shifting cultivation small scale. (iii) Foot and mouth – less sheep grazing etc.. – succession
– could also be +ve impact of humans – upgrading soil etc. through fertilisers etc.
 
If talking large scale in terms of biomes – human impact – deforestation, desertification – massive impact on both Tropical Rainforest / Temperate Grasslands
 
Yes spatial – is just comparisons between eocsystems – so spatial differences in productivity (hence learning your NPP figures / climate  / soils etc.. for various types of ecosystems (and not just TPR / Temperate Grasslands) or functioning (agan learning your different nutrient cycles) – remember I said that although the 2 you have to learn in detail is one grassland and one tropical rainforest – you still need to know your facts and figures from the fact files for the other biomes as you may need to refer to several smaller case studies if the essay is more general – for example spatial differences in productivity etc…. Also spatial variations – linked to human aspect – within Amazon – certain areas affected more than others – e.g. due to access – like around river.

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YEAR 13 – NOVEMBER 2008 – Preparing for Glaciation Test

Posted: Thursday 6th November

Firstly I must apologies for not being able to be with you this week – I will be back with you on Monday. Please remember as you have been told by Mrs Mottram, your GLACIATION TEST (for both groups) will be during the hour lesson on MONDAY 10th OCTOBER. I will then mark your test ready for parents evening on the Wednesday. To help you with your revision, below is a check list of what you need to learn. I have also included some summary notes – in particular on what you have been doing this week whilst I have been away – i.e. finishing glacial deposition (I have included my powerpoint), fluvio-glacial erosion (spillways and diversion channels) and living in lowland glacial areas.

Revision Checklist for Glaciation Test – Monday 10th November 2008:

1. GLACIAL EROSION PROCESSES

2. FACTORS AFFECTING GLACIAL EROSION RATES

3. GLACIAL EROSION FEATURES (e.g. corries, roche moutonnee etc. etc.) – formation and characteristics of and examples.

4. NAMED EXAMPLES OF GLACIAL EROSION AND DEPOSITION FEATURES

5. DIFFERENCE BETWEEN GLACIAL AND FLUVIO-GLACIAL DEPOSITS

6. GLACIAL DEPOSITION FEATURES – formation and characteristics of (see your notes on the different features – remember which are glacial and which are fluvio-glacial).

7. ADVANTAGES & DISADVANTAGES OF LIVING IN GLACIAL LOWLAND AREAS.

Below are some summary revision notes on the 3 areas that I have not been able to be with you for this week – please make sure you read these carefully and make sure you understand them – if they are helpful you can always print bits and add to your notes.

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1. GLACIAL DEPOSITION – remember we went through many of these features together before half term

I have included two powerpoints below – one of Glacial Deposition Features and one of Fluvioglacial deposition features. Remember we got up to looking at Kames on the fluvio-glacial features and this week you should have finished making notes on Kames and Eskers – I have included the powerpoint I used with you below for you to follow this up.

Powerpoint 1. Glacial Deposition

Powerpoint 2. Fluvio-glacial Deposition

Remember you should be broadening your knowledge and understanding by reading around the subject and there are also some excellent follow up links for reading around some of the glacial and fluvioglacial deposition features on the Fettes school site, particularly useful if you are finding it difficult to understand these features – try the following links:

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2. Glacial Spillways / Diversion Channels (THE ROLE OF MELTWATER IN EROSION)

Meltwater can have an important role in erosion and can affect drainage systems through forming glacial spillways and diversion channels.

GLACIAL SPILLWAYS

  • Pro-glacial lakes are found in front of glaciers, where the ice blocks a valley, enabling meltwater to build up in front of the glacier and bounded by the valley sides to form a lake
  • As pro-glacial lakes rise in height they may find cols (low parts in the valley side) over which they can flow into adjacent valleys – as they do so they cut deep channels into the lower valleys called spillways.

GLACIAL DIVERSION CHANNELS

  • As ice sheets expand they may also block the paths of rivers causing them to divert their course.
  • The River Severn for example once flowed north into the Dee Estuary. However during glacial times, the River was cut off by the ice and formed a pro-glacial lake this rose and flowed over a glacial spillway to flow south creating a glacial diversion channel, following a new course lower than the original and hence why the River Severn now flows south into the Bristol Channel.

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3. ADVANTAGES AND DISADVANTAGES OF LIVING IN A LOWLAND GLACIAL AREA

ADVANTAGES

  • Till deposits are fertile and well drained – for example East Anglia has good productive arable land as a result of the underlying glacial deposits
  • The reason for this is that mix of particle sizes helps drainage and the presence of fine clays retains moisture and the stones present retain heat. A range of minerals and nutrients are also often present due to the various origins of the mix of material
  • valley floors in upland areas are therefore good for dairy farming – e.g. Cheshire (heavy boulder clay providing natural pasture land) and also places in the Lake District
  • in some areas, ridges of moraine on valley floors have created dams to the down-valley flow of post-glacial streams and rivers creating lakes which have benefits for recreation and leisure
  • kettle lakes such as at Thetford, also provide benefits for recreation and leisure
  • fluvio-glacial deposits such as eskers have graded materials and are therefore often exploited for quarrying sands and gravels
  • likewise sand and gravels in terminal moraines although more mixed in size are useful in the construction industry.

DISADVANTAGES

  • some soils formed by glacial deposition, particularly in areas of high rainfall can be poorly drained and are subject to waterlogging which leads to marshlands and makes them unsuitable for commerical agriculture (e.g. the drumlin fields in Northern Ireland).
  • Fluvio-glacial outwash deposits of sand and gravel form infertile soils resulting in mainly heather vegetation which is of little economic value (however can be useful for recreation and tourism and sometimes used for military bases).
  • Glacial boulder clay is ‘friable’ i.e. can easily crumble and where coastlines, such as the Holderness Coast (Humberside) are made up of boulder clay, they are particularly susceptible to coastal erosion resulting in the loss of industry and settlement (refer back to your GCSE notes on the Holderness Coast for rates of erosion!).

Plus there is the department GLACIATION WEB – which has notes on glacial transport, deposition, erosion etc.. and a reminder of the Snowdonia fieldtrip!

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PREPARATION FOR THE SYNOPTIC PAPER – JULY 2007

Synoptic Skills (Question 1 on Synoptic Paper) – (50 MARKS)

The Synoptic Paper is a 2 hour paper containing 5 questions in total. You are expected to answer two of these questions. There are a total of 75 marks available.

Question 1 is compulsory – this is a skills based question and carries the bulk of the marks for this paper (50 marks). It has four sections to it (a – d), all of which must be answered. You are advised to spend 1 hour 15 minutes on this section. I suggest that you look at the questions and then spend the first 15 minutes interrogating the resources that you are given in the resource booklet.

The resource booklet for question one will contain a mixture of tables, graphs, text, photographs, diagrams and maps. You must make sure that you look at and use ALL the resources. During the first 15 minutes of going through the resources annotate them to draw out the key points, identify trends etc. Try and make any links between the resources – there will be ‘clues’ to the answers scattered throughout the booklet and you need to be using the resources and making reference to them.

Before answering the questions, read each question carefully and identify the command word – they often follow a pattern. Through the four questions you are likely to be asked to do the following: describe; describe and explain; examine and critically assess a viewpoint. It is important if you are examining or crticially assessing a viewpoint that you express your own view here.

Skills to develop in preparation for this paper:

  1. annotation of the resource booklet to pick out key points
  2. description of trends / patterns in data – spot general trends, look for anomalies and obvious inconsistencies (but don’t be tempted to talk through every little change)
  3. when describing relationships use terms such as positive and negative relationships and when describing patterns use terms such as clustered, uneven, linear, nucleated etc.
  4. use ALL material – they are all there for a reason – check that you have used them
  5. use your OWN WORDS – do NOT just lift chunks of text from resources – for each piece of text you use make sure you make a comment as to how it relates to the question
  6. be prepared to consider different points of view
  7. obey the command words and stick to it! (describe / explain / assess etc.) (a useful list of command words used in exams and their meanings can be found here)
  8. if asked to critically examine use phrases such as therefore, thus, however etc.

Make sure you have practiced all the past skills based questions from your Revision Booklet – remember read through the resources carefully and pay careful attention to the command words used in the questions.

  • June 2005 – Causes and Consequences of the growth of Las Vegas
  • June 2004 – Durban: The impact of urban development on the environment
  • Jan 2004 – Exploitation, Management and protection in the South Downs
  • June 2003 – Exploiting and Managing Resources – the Toshka project
  • Jan 2003 – The Effects of a Changing Environment in Alaska
  • June 2002 – Human Activity in Challenging Environments – the Isle of Skye

For further advice on how to write successful answers in Section A (Qu 1) of the synoptic paper you can download this summary which includes advice from the Teachers guide.

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Synoptic Essay (2nd part of the Synoptic Paper) – (25 MARKS)

Synoptic Essay Advice

As well as completing the compulsory question 1 (skills questions) worth 50 marks, you will need to select one essay (questions 2-5) worth 25 marks. At St Ivo we prepare you for question 2 (the first essay question), which looks at how Physical environments influence human activity.

Analysing the essay question

The essay titles in the synoptic unit are likely to draw on knowledge gathered from several links and will not ask for a particular process or environment. Make sure that you learn your case studies in detail to support your essay and to reach the higher marks.

When reading essay titles you need to highlight and deconstruct the essay to determine what is really been asked. First identify the essay topic (i.e. the subject matter being addressed / what the essay is about), secondly pay careful attention to the command word – what are you asked to do? e.g. examine, describe, analyse etc. You also need to ensure that you identify the focus of the question – i.e. the angle / point of view / range / location you are expected to focus on.

You should be able to apply the following phrases / words to the themes you have studied.

1. Short term and long term

  • This is a common focus, particularly when looking at the impact of hazards. However dependent on the context, the terms may vary – for example if looking on a human scale, short term is likely to mean hours, days, weeks or months, whereas on a geological timescale, thousands of years may be seen as short term for geologists.

2. MEDC or LEDC

  • We use the terms MEDC and LEDC to refer to More Economically and Less Economically Developed countries, but remember that in reality there are no clear divisions and many countries are between the two. Likewise you should always remember that there is great variation within countries.

3. Intentional or Unintentional

  • Intentional modifications of the environment – where policies and management decisions are taken with the intention in mind
  • Unintentional modifications – these are unpredictiable and unintended consequences of a modification of the environment.

4. Challenges and Opportunities

  • Challenges – refer to those challenges that are posed by environments that need to be overcome – e.g. challenges of living in a highland glaciated landscape (communications etc.)
  • Opportunities – refer to how environments can be exploited for social or economic gain (e.g. hydro-electric power generation in highland glaciated landscapes, or oil exploitation in Alaska)

5. Positive and Negative

  • Remember to be balanced in consideration of positive and negative effects as few actions / events are completely good or bad. Varying perspectives should also be considered as what is positive for some may be negative for others.

6. Rural and Urban

  • We can make contrasts between rural and urban environments, but remember that the distinction between rural and urban is increasingly hard to identify (particularly in MEDCs)

(source – summarised from Advanced Geography, N Yates et al.)

HINTS AND TIPS FOR ESSAY WRITING & MAXIMISING YOUR MARKS

  1. Start by Planning your essay for 5 minutes – this doesn’t need to be overdetailed but jot down quick ideas for the introduction, case studies to use for the bulk and points for concluding. (do not cross out your plan – you may be rewarded for it depending on content;
  2. When writing your essay ensure you use a clear structure – introduction, bulk and conclusion and you should make sure that you write in paragraphs
  3. Each paragraph shouldmake a point and you should illustrate it with an example – also try to make a reflective comment – e.g. “This suggests / demonstrates / shows that….” (also remember that quality of grammar, punctuation and spelling is assessed within the levels of the mark scheme)
  4. Keep re-reading the question and make sure that you are clearly answering the question in what you are writing (it is worth using the phrases every now and again from the question in your links to help ensure you are answering it);
  5. For level 4/5 essays, you need to make good use of case studies – to get these levels you need a wide range of exemplification, good locational detail and you need to illustrate your points with examples.
  6. Draw a good conclusion -this should not just be a precis – don’t just repeat what you have written, say something new – throw in a ‘pearl of wisdom’ or a twist – try and think through / learn possible conclusions to essays.
  7. Recognise variability and try not to be too one-sided in essays, construct arguments / present evidence considering various points of view. An A grade student is seen as one that argues rather than asserts – viewing the world as a complex place. You need to consider the various aspects of a topic in order to give a balanced – being evaluative is seen as a higher candidate skill;
  8. You can’t lose marks only gain them – so do not cross out anything you have written andif in doubt – put it in!
  9. Remember – you only have 45 minutes to write in so plan your essay and time carefully!

WHAT IS THE EXAMINER LOOKING FOR FOR YOU TO ACHIEVE TOP MARKS?

  • wide ranging and accurate descriptive knowledge
  • thorough explanation and balanced discussion of all aspects of the question
  • good understanding of geographical concepts used to support the arguements
  • examples are detailed – with a range of diagrams, maps and data used if appropriate
  • a range of scales is important- local – global
  • good English – fluent, expressing ideas clearly, few if any grammar, punctuation or spelling errors and good use of geographical vocabulary

Whilst revising, practice planning out essays and in particular draft out examples of introductions and conclusions and points you could include. You must also have some practice of writing under timed conditions.

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GOOD LUCK WITH THE PHYSICAL A2 EXAM!!!! (June 12th)

One the physical exam is out of the way I will post some advice / links etc. related to the synoptic unit for you.

REVISION TIME IS HERE!!! – MAY / JUNE 2008

Well we haven’t used the blog for a while as things have been quite hectic but I want to make use of it for revision to post some reminders and helpful revision resources. I will keep this at the top of the page but keep posting new things below – so keep an eye out!!

REVISION MATERIALS – 3rd June 2008

GLACIATION – REVISION NOTES

The following links provide summary revision notes I wrote a few years ago for the first couple of sections of the glaciation unit (not all of it I’m afraid!)

Plus remember there is the GLACIATION WEB – which has notes on glacial transport, deposition, erosion etc.. and a reminder of the Snowdonia fieldtrip!

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ECOSYSTEMS REVISION POWERPOINT

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PERIGLACIATION – PROCESSES AND LANDFORMS REVISION

I have just remembered these notes I wrote 2 years ago from the VLE pages – they may be useful as a revision tool for you!

Permafrost characteristics and an introduction to periglacial landforms and features

Periglacial Features 1 Solifluction lobes, asymmetrical valleys and valley camber and bulge

Periglacial Features 2 Involutions and Pingos

Periglacial Features 3 Ice Wedge and Stone Sorted Polygons

Periglacial Features 4 (features related to freeze thaw above ground – blockfields, scree; features of fluvial action – braided streams and dry valleys and features of aeolian action – loess, sandur)

Periglacial Features 5 – Nivation Hollows and Protalus Rampart

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GLACIATION REVISION QUIZZES

Some interactive quizzes that you may have forgotten about… (my apologies in advance – I’m sure in one of these there is a mistake and I can’t find it at the moment – if you spot it maybe you could let me know and I will change it – will also keep you on your toes!)

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Soils – Latosols / Ferralitic Soils

Just to make it clear that latosols are also known as ferralitic soils. Remember these latosols are the soils typical of the tropical rainforest biome, they are zonal soils. They often have poorly distinguished horizons due to leaching. The processs of ferrallisation, giving rise to the ferrallitic soils, is the process of iron / aluminium enrichment, it occurs as the clays within the soil break down quickly under the hot/humid conditions and rapid leaching of silicates occurs down to lower levels. However as iron, aluminium and manganese minerals are relatively insoluble they remain in the upper layers. It is this accumulation of iron oxides in the upper layers which gives rise to the characteristics red colour of the latosols / ferralitic soils.

There is a good animation of latosol/ ferrallitc soil profiles here on the Wycombe Geography site

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Cheluviation (Soil Process)

Nutrients and organic acids, known as chelating agents are released during the decomposition of organic matter. These attack clays and other minerals in the A horizon and release iron and aluminium. The chelating agents combine with the the cations of the iron and aluminium forming soluble chelates (organic metal compounds). Cheluviation occurs as these chelates are transported down through the soil. Lower down the profile, the pH is slightly higher and iron and aluminium may be deposited here.

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What is a thermokarst landscape and how does it develop?

Thermokarst is an uneven landscape with hummocks between shallow depressions and pits and troughs. It is formed where there is extensive thawing of ground ice causing material to collapse into the spaces once occupied by ice. For example, this may occur where ice wedges thaw leaving behind elongated depressions and where the ice cores in pingoes melt, collapsed pingoes characterised by circular depressions with raised rims are formed (ognips). Thermokarst landscapes are also the result of the irregular distribution of sands, silts, gravels etc. within the ground. As they have different water holding capacities e.g. gravels more free draining than silt, differential rates of freezing will occur. This results in the formation of involutions under the ground, as the advancing ice layer descends at the end of the summer, when the active layer re-freezes putting these sediments under pressure. Again this will give rise to a very uneven surface layer. Thawing of the ice may be due to climatic warming or may simply be due to the modification of local conditions, e.g. disturbance to vegetation cover exposing ice cores.

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Remember your essay writing skills – here is a nice reminder from Wycombe High School on Writing Good A’level Essays (includes command words – but you should have these already)

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SOILS

I meant to mention this link to you a while ago (I may already have – so apologies if I have) – but this is a great section from the Wycombe High School site – including some useful soils animations!

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Revision Request – Mass Balance / Glacial Budget

A glacier is a system and is the product of the balance between inputs, stores / transfers and outputs.

The upper part of the glacier is known as the zone of accumulation – this is where inputs exceed outputs. The lower part is known as the zone of ablation and is where outputs exceed inputs. Where rates of accumulation and ablation are equal this is known as the zone of equilibrium.

The glacial budget (mass balance) is important in the development of the glacier system, it is the balance between accumulation and ablation over a year.

Over a year – glaciers expand and contract due to mass balance changing with the sesons. Whether a glacier grows or shrinks over a longer period depends on mass balance averaged over a year – the NET BALANCE (if accumulation in winter = ablation in summer – annual net balance = 0).

  • +ve mass balance – accumulation > ablation – ice grows and the snout of the glacier advances (normally winter) – i.e. net gain of ice throughout the year – the firn line moves down the valley
  • -ve mass balance – accumulation < ablation – ice decreases and the ice front retreats (contraction of the glacier) (normally summer) – i.e. net ablation – there is an up valley movement of the firn line.
  • Where accumulation and ablation are equal – the glacier is in equilibrium and will remain stable in its position.

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Revision Request: Growth and Decay of Ice Sheets

Just a few points to remind you of some of the factors influencing the growth and decay of ice sheets:

Factors influencing the growth of ice sheets:

  • growth of ice sheets results from accumulation of ice
  • climate is the main control – in winter the main precipitation is snow – shorter summers means less time for ablation therefore snow becomes permanent throughout the year
  • further snow will fall resulting in the gradual accumulationof ice – gradually turning from snow – firn (neve) – true glacial ice
  • Aspect is also important – permanent snow-line is at a lower altitude on north-facing slopes

Factors influencing the decay of ice sheets:

  • decay of ice sheets results from ablation
  • where summer temperatures are high – resulting in ablation, if outputs exceed inputs, the ice will retreat (i.e. a negative mass balance.

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Revision Request: Photosynthesis

The process of photosynthesis is essential to life on earth. Whilst heat energy cannot be trapped by plants or animals, light energy can be trapped by green plants which are known as autotrophs (’self-feeders’). These have the ability to produce their own sugars and food from inorganic compounds. The suns energy is trapped by ‘chlorophyll‘ which then converts solar energy, carbon dioxide (absorbed through stomata in leaves) and water (taken up by roots), into chemical energy (glucose) and oxygen. For effective photosynthesis to occur, temperatures usually need to exceed 10oC, where the air temperature falls below 6oC, plants tend to cease to produce chlorophyll and therefore photosynthesis ceases. Through photosynthesis, energy is produced for the producers to use in growth and respiration, and reproduction – food energy is also created which can be consumer by herbivores at the start of a food chain. The by-product of photosynthesis is essential for animal life on earth.

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Corrie Formation

Following a request on the blog to go over corrie formation – here is a simple sequence of events which results in the formation – do be prepared to be able to draw labelled diagrams to support your essays – diagrams and examples where appropriate are often credited in the highest mark bands if well used!

A simple sequence of corrie formation:

  • the process starts with the development of a small hollow in which there is the annual accumulation of snow – the hollow is enlarged by nivation processes (set of processes operating underneath / near to the snow – including freeze thaw, solifluction etc.)
  • continued enlargement occurs and as further fresh snow falls, compression of snow results diagenesis with continued compaction of snow resulting in the eventual formation of true glacial ice.
  • As the ice reaches a critical depth, rotational movement of the ice under its own weight occurs resulting in deepening of the base of the hollow;
  • As rotational movement results in extending flow, plucking of the back wall occurs making it steeper
  • This plucking creates debris and further debris is available from rock fragments falling into the bergschrund (at back) – the availability of debris under the ice allow abrasion to further erode the hollow
  • Due to the deepening of the hollow, ice at the front is thinner and therefore has less erosive power leaving a rock lip at the end which may also contain moraine deposits
  • In post glacial times, corries are often occupied by glacial lakes known as tarns.

(references drawn on – Yates, N – Advanced Geography)

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GLACIER MOVEMENT – 30th April 2008

Ok – having been marking your 5 mark answers on “Distinguish between the mechanisms of movement in polar and temperate glaciers” I thought I would highlight a few resources on glacier movement. Remember the essay could have been a 20 mark one including ideas on factors affecting rates of movement so you should be prepared for this.
To start with have a look at this useful website summarising Glacier Movement (British Society for Geomorphology).

NOTES FOR THE GLACIAL DEPOSITION ESSAY – 30th October

My sincere apologies for the delay in uploading this – here are the notes from the essay plan we created on the IWB (essay_glacial_deposition.pdf) – they are in .pdf format (so you will need adobe acrobat reader to view them).

Week Beginning 15th October 2007 – Post 2 Glacial Deposition

This week we continue to look at the processes and landforms created by Glacial Deposition. Remember the collective term for all glacial deposits are glacial drift. We can look at two types of deposition – direct deposition by ice and indirect deposition by meltwater and ice-contact stratified drift. The deposits of direct glacial deposition (lodgement and ablation till) and fluvioglacial deposits can be distinguished from each other by their distinctive characteristics. Remember glacial deposits are unsorted (a random mix of large and small stones), are fairly angular in shape (although have lost the jaggedness of frost shattered material) and are unstratified. In contrast fluvio-glacial deposits are sorted (largest material deposited first as water looses its energy and drops the heaviest material first), stratified (layers of material due to annual variations in meltwater) and more rounded in shape (due to the influence of attrition – as rocks and debris knock against each other within the waters flow).

We started this week looking at glacial till deposits (unsorted, unstratified and angular) and the landforms that are created. Remember these include: drumlins, moraines, erratics and till plains.

The powerpoint below is the one used in class and may help you when revising these distinctive deposition features.

Remember you can also use many of the points we have discussed should you have an essay concerning fieldwork evidence for the extent and direction of ice movement – for example:

  • Drumlins – the long axis is parallel to the direction of ice movement (also case studies in your notes too look at how drumlin shape etc. can indicate patterns of ice movement – see case study sheet – Lake District)
  • Erratics – can indicate the power and direction of the ice movement (you have examples in your notes – to help illustrate this e.g. Alisa Craig, Norber erratics etc.)
  • Morraines can indicate the extent of flow – for example the terminal moraine marks maximum extent of the glacier and recessional and push moraines can indicate periods of advance and retreat.
  • Till plains – till fabric analysis – remember this involves measuring the orientation and dip of the long axes of stones from a till sample. A rose diagram can be used to indicate the general orrientation of the sample and it is believed that the stones in ground moraines align with the ice, parallet to the direction of flow – thus allowing reconstruction of the direction of ice movement (again see case study sheet).

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Week Beginning 1st October 2007 – Post 1 – GLACIAL EROSION

My apologies for not being able to start the blog earlier – things have been a bit hectic – I will over half term add some links to the topic areas we have already covered this term – i.e. on Glacier formation and distribution; types of glaciers; surface features (crevasses and moraines). As it is I am going to start my blog posts on the work we have been doing on Glacial Erosion

The specification states that you must know.. Processes of glacial erosion (plucking and abrasion) and weathering and factors influencing the rates of these processes.

Remember – there are 2 main erosion processes (i) Abrasion and (ii) Plucking, however sub-glacial water erosion is also an important erosion process active in temperate glacial environments. Weathering processes such as dilation (pressure release) and frost shattering can help to facilitate glacial erosion by making these processes more effective (for example through opening up joints in rock, enabling more effective plucking etc.)

Your first essay of the year is based on glacial erosion:

1. Distinguish between the glacial erosion processes of abrasion and plucking (5 marks)

2. Assess the relative importance of the factors influencing rates of glacial erosion (20 marks)

DUE IN: Monday 8th October 2007

Remember to plan your essay carefully and consider its structure carefully. A clear beginning, middle and end structure is required.

ESSAY WRITING SKILLS:

We have talked these through in class – but you should also read this excellent guide on how to write a good A2 Essay in Geography from Wycombe High School’s Geography Department. Essay writing is going to be the key to your success at A2 and you are going to be writing many essays over the year – over the next few weeks you will be given advanced warning of some of the essay titles you will be tackling this term.

Resources for your Glacial Erosion Essay:

As well as the Geography textbooks in the department and in the Resources Centre (yes you should be carrying out research!), you should find the following resources useful..

And to help you with the essay and for revision purposes, here is the powerpoint on Glacial Erosion we have used in class.

If you have any questions about the essay, you can either add a comment here on the Year 13 blog page (but no surnames please), or e-mail me.

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One Response to “Year 13”

  1. Lizzie Says:
    June 4, 2008 at 12:36 pm

    i have my geography a2 exam in 2 days and found your site invaluable and SO helpful! thank you!

    Reply

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