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Size and shape of rock fragments
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As rock is weathered, the broken pieces fall from the original piece of rock and form a pile at the bottom of the rock face. This often forms quite a smooth slope called a scree slope.
The fragments of rock vary in size from large boulders to tiny grains, and the shape also varies from piece to piece.
These fragments have fallen from the rock face onto the scree slope and have remained there.
Remember the words:
particle – частинка pile – купа rock face – вихід гірських порід на поверхню, відслонення slope – схил scree – кам’янистий осип vary – різнитися, відрізнятися boulder – валун tiny – дуже маленький, крихітний to remain – залишатися
Answer the questions:
1. What happens when rock is weathered?
2. What do the broken pieces of rock form?
3. Where is a pile of broken pieces formed?
4. What do we call a “scree slope”?
5. What is the size of rock fragments?
6. Are all rock fragments of the same shape?
7. Where do the rock fragments remain after they have fallen from the rock face?
Exercise1. Render the following to the past beginning with: we learned that…, we knew that…, the teacher told us that…, the teacher said that…
1. On the earth surface the rock will be weathered.
2. The pieces of rock will break off.
3. The broken pieces will form a pile at the bottom of the rock face.
4. A scree slope will be formed.
5. The fragments of rock will be of various forms.
6. The size of rock fragments will vary.
7. The rock fragments will fall from the rock face.
8. The fragments of rock will remain on the scree slope.
Transportation of fragments
If there is fast flowing water passing by the fallen rock fragments then some of these fragments (maybe not the huge boulders!) will be swept along by the water current. This can do two things:
1. It can move them, sometimes huge distances.
2. It can change their shape, as they bounce off other large particles.
Many particles become slightly smaller and more rounded in shape as they move down the river bed.
Larger grains are not carried as far as smaller grains since it takes more energy to
move them. As the river flows quickly down the mountain side it will carry a range of particle sizes, but as it levels out and travels more slowly, the larger grains are deposited as sediment.
This means that particles of a similar size are deposited at the same time, and in the same place. These form sediments and often show a clear distinction between different kinds of particles.
Remember the words:
to flow – текти, литися huge – величезний
to sweep – зносити, змивати current – течія
to bounce – підстрибувати, відскакувати river bed – дно річки, річище
to carry – нести, переносити range – ряд
to level out – нівелювати, вирівнювати deposit – відклад, поклад, родовище
similar – подібний, схожий same – той самий, такий самий
clear – ясний, чіткий, зрозумілий distinction – різниця, відмінність
Answer the questions:
1. On what condition will rock fragments be swept along?
2. What will they be swept by?
3. Why can rock fragments move, sometimes huge distances?
4. Why do rock fragments change their shape?
5. How do rock particles change their shape?
6. Do larger and smaller grains travel the same distance? Why?
7. What happens to larger grains when the river levels out?
8. How are sediments formed?