A lagoon is a 咸水湖. It's an enclosed water body (salty water), usually enclosed by a sand bar / snd spit near the sea. It may also be found in inland area, usually in a basin where all the water plus the mineral salts are drained into the lake in the middle of mountains.
It may dry up one day if there is no continuous supply of water. It will first turn into marshland / swamps and then turn into a new piece of land formed by deposition.
on Tb p.2.63- Blow-holes. (a) "Why Cheung Chau Cheung Po tsai cave donnot have water inside, just can feel a little bit wet only? Is it given eroded or.....? Where is the hydraulic action of waves? (b) Why there is a hole on the top of sea cliff? How can we know that there is a sorm happened in the sea?
Ms Leung's response:
Cheung Po Tsai cave is an emerged landform. It is raised above sea level OR the sea level dropped.
On Tb p.2.63- How can we clarified the types of beaches? There are sandy beach, pebbles beach and boulder beach.
Ms Leung's response:
There is definition for snad, pebbles and boulder (i.e. particle size). Pls refer to this website (pls click the icons): http://www.wiley.com/college/strahler/0471480533/animations/ch12_animations/animation2.html
Why the sea wall needs to be curved when facing the sea?
Ms Leung's response:
Good observation! Some sea walls are curved while some are stepped. Some are even rubble-covered. (Pls refer to this document: http://140.194.76.129/publications/eng-manuals/em1110-2-1614/a-c.pdf )
I think it’s related to physics力學問題. Science students from 4A, 4B and 4C, who’d like to try this question?
To nourish a beach, it is important to keep the water clean. Sewage in the nearby settlement should be treated first, before dumping into the sea.
Just like the case of Lung Mei beach, the water quality is poor because all the untreated sewage from the nearby villages are collected into a sewage pipe discharging it into Lung Mei. When an artificial beach is built in Lung Mei, the sewage pipe will be extended a distance away from the beach (but tides will bring them back).
Question 1.
回覆刪除I am not understand the true meaning of "offshore"
Ms Leung's response:
It's the coastal area always under the lowest tide level, i.e. always in sea water.
Question 2:
回覆刪除What are the characteristics of laggon?
Ms Leung's response:
A lagoon is a 咸水湖. It's an enclosed water body (salty water), usually enclosed by a sand bar / snd spit near the sea.
It may also be found in inland area, usually in a basin where all the water plus the mineral salts are drained into the lake in the middle of mountains.
It may dry up one day if there is no continuous supply of water. It will first turn into marshland / swamps and then turn into a new piece of land formed by deposition.
Question 3:
回覆刪除on Tb p.2.63- Blow-holes. (a) "Why Cheung Chau Cheung Po tsai cave donnot have water inside, just can feel a little bit wet only? Is it given eroded or.....? Where is the hydraulic action of waves? (b) Why there is a hole on the top of sea cliff? How can we know that there is a sorm happened in the sea?
Ms Leung's response:
Cheung Po Tsai cave is an emerged landform. It is raised above sea level OR the sea level dropped.
question 4:
回覆刪除On Tb p.2.63- How can we clarified the types of beaches? There are sandy beach, pebbles beach and boulder beach.
Ms Leung's response:
There is definition for snad, pebbles and boulder (i.e. particle size). Pls refer to this website (pls click the icons):
http://www.wiley.com/college/strahler/0471480533/animations/ch12_animations/animation2.html
Question 5:
回覆刪除What is ' Storm waves'?
Ms leung's response:
Big waves formed during storms. Pls refer to the footages of this website:
http://www.oceanfootage.com/stockfootage/Storm_Waves
Question 6:
回覆刪除Why the sea wall needs to be curved when facing the sea?
Ms Leung's response:
Good observation! Some sea walls are curved while some are stepped. Some are even rubble-covered. (Pls refer to this document: http://140.194.76.129/publications/eng-manuals/em1110-2-1614/a-c.pdf )
I think it’s related to physics力學問題. Science students from 4A, 4B and 4C, who’d like to try this question?
Question 7:
回覆刪除Why toe protection is need to place in front of the sea wall?
Ms Leung's response:
Smart question! Let me divide this question into sub-questions:
1.Where is the toe of a sea wall?
2.What is done at the toe of a sea wall?
Imagine how we protect our toes by wearing shoes. There are many different types of shoes. There are many types of toe protection for sea walls too.
Pls refer to this link:
http://www.tendringdc.gov.uk/NR/rdonlyres/8DDD624E-4FA2-4535-8529-5CA37714B104/0/ArchiveCliffParadeWalton.pdf
Question 8:
回覆刪除Why beach nourishment also need sewage treatment?
Ms Leung's response:
To nourish a beach, it is important to keep the water clean. Sewage in the nearby settlement should be treated first, before dumping into the sea.
Just like the case of Lung Mei beach, the water quality is poor because all the untreated sewage from the nearby villages are collected into a sewage pipe discharging it into Lung Mei. When an artificial beach is built in Lung Mei, the sewage pipe will be extended a distance away from the beach (but tides will bring them back).
Question 9:
回覆刪除Why vegetation planting on cliffs can increase their stability then stabilize the shore?
Ms Leung's response:
This is something you learnt in S.1. Remember the chapter “unstable slopes”? Two forces are working on slopes: strength & stress.
Do you think vegetation planted on slopes can increase the strength OR can decrease the stress of a slope?
But this engineering measure to stabilize slope is debatable. Do you find many man-made slopes in HK planted with a lot of trees? Why not?