♥ Monday, April 27, 2009 ♥
Hello I'm being responsible and blogging today! (like right after today's lesson)
Haha hooray me, and for us! :D
So firstly, we learnt about
THE RIVER PROCESSES today. :)
Basically,
deposition->
transportation ->
erosion.
Which means that, after deposition, if there is still excess energy, transportation will take place, and again, if there is still some more excess energy, erosion will take place.
Now, let me show you a graph, which would help to enhance your understanding! ;)
Critical erosion velocity (the Hjulstrom curve)
Okay, I hope that you've understand the first part of today's lesson.
Next, we went deeper into the transportation process!
- Traction- Heaviest/Largest material is rolled along the river bed, and this requires the most energy out of all the subgroups.
- Saltation- Sand-sized particles bounce along the riverbed in a "leap-frog" motion.
- Suspension- Smaller particles (silt and clay-sized) are carried within the water by turbulent flow. Turbulent flow refers to water not flowing straight. :)
- Solution- Some minerals will be dissolved in the water and will be carried in the solution, and this requires the least energy.
Now moving on, if there is still excess energy, erosion will take place.
There are 4 types of erosion:
1) Corrasion
2) Hydraulic Action
3) Solution
4) Attrition
Corrasion, or also known as Abrasion, targets the bedrock. The nature of corrasion is either called the 'drilling' or 'sand paper', which is the rubbing effect on sediments. The outcome of this process are potholes banks, which are wider and also smoother because of the 'sand paper effect'.
Hydraulic Action, or also known as Weathering, targets cracks. The nature of this process is air pressure. Air pressure increases when water seeps into the cracks, and air pressure decreases in the cracks when the water flows out. This will cause the cracks to expand, and it is an explosive process. The outcome of this process are collapsed banks.
Solution, targets the bedrock too. Bedrocks are rocks which have not been weathered yet. And the nature of this process is chemically driven.
Attrition, targets the sediment load. And this process takes place because of the impact of the sediment load constantly knocking against each other. The outcome of this process is the formation of smaller and rounder rocks.
Its the end! Haha yay aren't you glad, thats all! (for the erosion process) ;D
Now imagine a hill...
Okay nevermind, I shall attempt to draw it out for you on paint! :/
There you go! HAHA :)
Now to explain about the River Valley...
Upper Course takes the shape of a V-shaped valley due to mass movements, such as landslides and avalaunches. This is called vertical erosion, which deepens the bedrock channel, thus forming landforms like the Grand Canyon.
This beautiful picture shows the famous Grand Canyon of Yellowstone. The V-shaped valley is very obvious in here. :)
Middle Course takes the shape of a wider and flatter valley as a result of the sediments being already weathered, and broken down. This can also be named as alluvial. There is increased sinuosity, which means the distances widens and increases, which forms landforms like meanders and grasslands.
This picture shows a typical meander along the grassland. Notice that the grassland is much flatter and wider than the valley along the upper course. :)
Lower Course also takes the shape of a wider and flatter valley. The reason to this formation is exactly the same as how the middle course forms a wide and flat valley. At the lower course, floodplains and levees are the types of landforms formed.
The picture shows a floodplain, which is flat or nearly flat, and is adjacent to a stream or river. This position causes it to be flooded occasionally. :)
Hope you enjoyed reading this post!
Haha alright, see you people around.
By, Joel Tay (22)
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hiie, i was totally amazed by what we learnt today. When I think about how water comes about, I'll always just think about the hydrological cycle which we've learnt previously and have never thought of how water sources such as river comes about. Today, I have learnt about the different processes that occur in river and the energy level that brings about the different processes. Last year, I've learnt how volcanoes are formed, and this year, I've learnt how rivers are formed. I hope to learn more about the formation of these wonderful natural features. =)
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Haha yes of course! Nature is so interesting huh, about volcanoes, the atmosphere & hydrosphere, and their its landforms like waterfalls, meanders, and valleys, etc.! :) okay, all the best for the 20% test tomorrow people! :D
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oh...i missed out this lesson and i totally forgot we can get the information from here!!!:P
it is really amazing and the pictures are so fantastic:) i think i found out a bit late..eh..so long after the test already. anyway, learning geog is not only for the test, right?! we learn it for fun!haha, so interesting!i'd like to read through my notes again:):)
hold on,i got one question. for transportation, why clay-sized particles need least energy to be carried? i thought there is a possibility that they would stick together and then may be harder to carry???
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hiie, i was totally amazed by what we learnt today. When I think about how water comes about, I'll always just think about the hydrological cycle which we've learnt previously and have never thought of how water sources such as river comes about. Today, I have learnt about the different processes that occur in river and the energy level that brings about the different processes. Last year, I've learnt how volcanoes are formed, and this year, I've learnt how rivers are formed. I hope to learn more about the formation of these wonderful natural features. =)