Regarding format of the comment block.

I've changed the way the comment block appears in every entry because I think this format will be more convenient as you guys can refer back to the entry itself while commenting.

All the best.
Minh.

(Haha, jusk asking, can the changes made to the format of the blog be counted as 1 comment for me? :D).

Summary

Time flies really fast doesn't it? Well, that's a good cause MR HEAH IS BACK!!!!!! :DDDDD

so basically here are the things we have learnt throughout the term

Key Learning Points

1) How different things interact and work together to form a system

2)Balance is essential in every system

e.g. Thermodynamic equilibrium

Sara's example: Carbon dioxide, too little and we will freeze to death, too much and we will have global warming.

Its ironic that we are messing up the very balance that is keeping us breathing

3) Structure and composition of the atmosphere

-Nitrogen: 78%

-Oxygen: 21%

-Carbon Dioxide: 0.03%

-Other gasses: 0.97%

4) Importance of the atmosphere

-Block out UV rays

-provides oxygen

-keeps the Earth warm

5) The classic "place shapes people, people shapes place",that we have been learning since last year. Let's name this Heah's law :D

e.g. eskimos adapting to live in the cold

6) Global warming

WE HAVE TO DO SOMETHING ABOUT THIS PEOPLE!!!

7) The different types of rain, how do they occur and when do they occur.

-Relief (contributes to the formation of deserts)

-Frontal

-convectional

(adiabatic cooling is involved in all of the above)

8) Climate and weather

These 2 can always be seen as how warm and how wet a place is and is also dependent on its latitude and longtitude.

9) How to read a climograph

Apart from reading from the graph, we would also have to interpret the data or else all those numbers would just be useless.

10) Seasons and its relevance to the tilt and shape of the Earth

(refer to Minh's post dated February 23rd, very detailed)

11) How winds move

-The 3 cells (Hadley, Farrell and Polar)

12) Deserts

To clear up a common misconception, deserts are not formed where it is very warm, but rather where it is extremely dry. This can be expained byt the direction of winds which carry the water vapour which ultimately results in percipitation. :D

-Formation can be explained by tricellular model or relief rain

13) Drainage basin

-What happens to percipitation (Infiltrate, throughflow, baseflow, interception, throughfall, stemflow etc)

14) Hydrographs

-How to read them

-Its use (to predict the chances of flooding and how authorities have to evacuate the people before it starts to flood, or before the situation worsens)

In this case, the lagtime is very important to determine how much time they have to evacuate

-The factors which affect the shape and height of the hydrograph (shape,size, geology, etc)

15) River processes

-Transportation (the different types of loads)

-Erosion

16) Braided channels and deltas

17) Meanders

caused by -Diff velocities at diff parts of river

- Helicodial flow

How it can result in an oxbow lake

LIFE SKILLS

BE CONCISE

NEVER MEMORISE, UNDERSTAND

BREAK DOWN QUESTIONS

ITS ABOUT THE QUESTION NOT THE ANSWER

Change in Blog Format by Minh.

Hi everybody!!!
I've just changed the blog format so that hopefully it would be easier for all of you to edit your own post and make comment.
Best regards,
Minh.

Hello. Today, we just did some revision and we were asked to read up on the water formations along the river such as waterfalls, meanders and oxbow lakes. So, I shall now try to revise for you what meanders are and teach you what oxbow lakes are.

Meanders

A meander is a bend in a river, normally at its middle or lower course where the channel is deeper and wider, which is caused by two things:
a) the difference in velocity between the inside and outside bend of the river
b) helicoidal flow

A. There is a difference in the velocity of water between the inside and outside bend of the river. Water flows faster on the outside bend of the river (because water is flung out of the bend as it curves through the outer bend, causing greater erosion, resulting in a deeper channel and thus, less friction). This is why the bank of the outer bend is steep (refer to picture).
It is opposite in the inner bend where the water is slow moving due to a shallower channel and more friction, causing deposition rather than erosion. This material deposited builds up and creates a slip-off slope (refer to picture).
Hence, because there is higher velocity at the outer bend, erosion happens and vice versa for the inner bend, creating this wondrous formation - MEANDERS!

B. Besides that, helicoidal flow, which is water flowing in a spiral, means that water does not flow straight, so there will be meanders.





Oxbow lakes

Following up from meanders, it is (so) obvious that as a meander gets more and more meandered, the difference in velocity will become even larger because the inner bend will have collected so much deposition that it is much shallower than the extremely eroded outer bend, so as a river is more and more meandered, it will cause it to become even MORE AND MORE MEANDERED! It is a kind of positive feedback thing….

So what happens when it gets so meandered that the river actually joins together again? You will get an oxbow lake! Look at the picture and you can see that as it gets super meandered, the neck of the straight paths is only separated by a little land. So, the water can just break through, leaving the meander out of the river. Soon, this oxbow lake will dry out because it won’t receive any of the river’s water and it will become a meander scar.

So, there. Now you know what oxbow lakes are. Thanks for reading this. You have just wasted 5 minutes of your life trying to understand me because all you had to do was watch this animation (http://www.cleo.net.uk/resources/displayframe.php?src=309/consultants_resources%2F_files%2Fmeander4.swf) which is everything I just said. :D

The end.

Done by WENG KIN.

Geography rocks! (get the pun? :D)

PS: You can also read http://geobytesgcse.blogspot.com/2006/11/middle-course-of-river-meanders-ox-bow.html

Braided Channels and Deltas

Ok, this is my first blog entry and may be my last post also (unless we have 22 more lessons :D).
Today lesson, we've come up with two concepts: braiding and deltas. Now I'm going to do some recap for you guys.

1) Braiding:
- A braided channel is a river within which the stream is divided into smaller and interlacing channels by small islands called "bars". (the picture looks like a bunch of epidemal cells, really)
- These bars are sediments deposited by the river and are very firm (in Bangladesh, people make use of these islands to build house on) because when old sediments are removed, new ones will arrive and be deposited at the bars
- Causes of this braiding features:
+ The river banks are easily eroded (materials from the banks will form the bars)
+ The more abundant the sediments are, the bigger and more of bars will be formed
+ If the river's discharge changes, formation of bars also changes. If less discharge, the river's velocity as well as its ability to transport sediments decrease and vice versa.
+ It also depends on the gradient of the river, if it's steep, velocity of water is greater and hence less deposition occurs. If the water flows more slowly, materials are easily dropped along the way.

2) Deltas:
- When a very large amount of sediments is deposited at the river mouth, materials will be piled up and new lands are formed here. These lands are called "delta".
- The river then has to divide to smaller channels called "distributaries" to overcome these blocks
- There are two types of Delta: arcuate and bird's foot (why not bird's feet???) but since (Miss) Peixin didn't say anything about them so i'm not going to mention here.

Extra stuffs about Delta:

Introduce you guys to the largest Delta in Vietnam!!! We call it "Đồng bằng sông Cửu Long", as translating to English, it'd mean "Nine Dragons river delta":

This Delta is formed at the mouth of the Mekong River. As you can see in the picture, the river itself has divided into 9 (nine) (:D) distributaries, that's why it's called "Nine-dragons...". In this area, people rely heavily on agricuture due to the rich of alluvium brought by the river.

OK that should be it :) Before i end my entry and go mug Chem stuffs, i want to remind you of the contents tested in assessment paper:
+ Atmosphere: - Climates, seasons
- Climograph
- Heat balance (no need to remember all the numbers but if you want to challenge your brain, then go ahead :D)
- Rain formation (adiabetic coolings, movement of air, types of rains)
* No global warming stuffs
+ Hydrophere: - Hyrpgraph
- Drainage basin (not sure about this)
- River channels processes
- Formation of waterfall
- River's features.

OK done! Have fun! :)

Vu Ngoc Quang (aka CT rep :D) 5/5/2009

Today (24/4) Ms Lin walked into class.

and basically covered some new content that was essential to the following lesson's discussion.

Upper Course	Middle Course	Lower Course
V-shaped Valley	Wider flatter valley	Wider flatter valley
Mass movements	Wider and deeper channel Alluvial(loose material like sand/sediments)	Wider and deeper channel Alluvial(loose material like sand/sediments)
Vertical erosion (Bedrock[hard rocks] channel)	Increased sinuosity	Floodplains and levees

THEN we went onto River Processes and sedimental transportation

Ways that sediments can be transported

1. Traction - heaviest material that rolls along river bed requires the most energy to carry

2. Saltation - Rocks bounce 

3. Suspension - Small particles like salt/clay/sand that is carried with water through turbulent flow. The MAIN form of sediment transfer

4. Solution - Minerals dissolved

Processes of erosion

The excess kilojoules of a river is harnessed to erode, the process of picking up and removal of material.

 

	Corrasion/Abrasion	Hydraulic Action	Solution	Attrition
Targets	Bedrock	Cracks	Bedrock	Sediment load
Nature	Drilling/sand paper	Pressure	Chemical	Impact
Outcome	Vertical/lateral erosion	Collapsed bank		Smaller/rounder

Erosion of RIVER CHANNEL

Sandpaper - the sediment load rubs against load, in collision

Hydraulic Action - Water enters the holes/cracks, which results in increased pressure. The air bubbles burst after heavy compression

Attrition - High pressure just result in impaction, collision 

There was this Velocity-Particle grain size(diameter) graph shown which shows the velocity needed to carry a certain coarse material. However, the values of the graph cannot be considered seriously because not all particles are round.

So after these mundane content we started looking at pictures! Such as deltas...meanders...etc. and apply our knowledge!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

taro

Friday 17th April 2009 =D

Today we did a recap on River Processes:
1) Erosion
2) Transportation
3) Deposition

So basically, the river erodes the rocks or soil and transports it and then deposits it when there is not enough energy left to carry it. (details are in the previous post by DL =D )

So we went over to the concept of Energy!

What affects the energy of the river?
- Discharge, which is the amount of water
- Velocity, which is based on the gradient, the cross-section/channel shape, and friction)

Discharge is easy to understand. If the river has more water flowing, it has more energy =D

Gradient too, if the river is more sloped (say, a waterfall, then it has more energy)
This is due to gravity:

Remember this?

Oh the horror...

Now for Channel Shape.
If the channel is narrower, there will be less friction for the water because there is a greater wetted perimeter/ greater amount of water in contact with the perimeter, thus wetting it/ greater- oh i dunno what la...
(wikipedia puts it as 'the greater the wetted perimeter, so there =D )
Also, wetted perimeter = the cross-sectional area that is 'wet' (courtesy of wiki as well xD)

So a river channel like this

will have more friction than one like this


supposedly, but won't the additional water that figure 1 can hold make up for the increase in the wetted perimeter, thus having a canceling effect or something?

ANYWAY, lastly, we have friction =D
This changes with different types of rocks

Next, we split into groups to try and predict how velocity changes from source to mouth.
btw, the source is defined as the tributary that is furthest away from the mouth =D

My group said that it varies because the friction due to greater wetted perimeter cancels out with the greater amount of discharge, so it's mostly dependent on the gradient, which can change randomly =D

The correct answer, anyway, was that velocity increases downstream as the eroded rocks get smaller and rounder, sediment load decreases, so velocity increases downstream =D

KK so that's basically what we did for lesson xD with this final extra question:
Will a group of salmon travelling upstream to, let's say, Bread, affect the velocity of the river?
My answer: No! xD

Here's a diagram why:
oh look, a fish!
Fishie wags his tail...


Fishie moves forward, Pushing the water infront of it infront...

So now we have a swarm of salmon...

AND VIOLA!!! (i'm sure i spelt this wrongly)
THE ARROWS CANCEL EACH OTHER OUT!!!
you can see that there are the same number of front-arrows as back-arrows =D

And this concludes LLJ's FISH THEORY OF CONSTANT VELOCITY

(All pictures courtesy of ME and Macromedia Fireworks xD [seriously, you all should get this])

Current Geo Challenge Score: 1833 (T.T)

Oh well...

Until next time then...

Well-Wishes
LiangJie

MR HEAH GET WELL SOOOOON!!!!!!!!! <3 (hahas yes i just typed that)