Rivers and coasts, Year 8: more practice：全部卡片
整套按顺序列出——孩子看到之前，您可以先通读一遍。
- What is it called when seawater is forced into cracks in a cliff, compressing the air and widening the cracks?
Hydraulic action
提示The sheer force of the water itself does the work.
为什么Each wave pushes air in the crack under pressure, and as the water drains back the air expands. Repeated again and again, this breaks rock apart.
- Why does a headland of hard rock stick out into the sea while a bay of soft rock lies beside it?
The soft rock erodes faster, leaving the hard rock behind
提示Compare how quickly different rocks wear away.
为什么Waves cut back soft rock such as clay more quickly than hard rock such as chalk or granite. This is called differential erosion.
- A waterfall forms where a river flows over hard rock lying on top of soft rock. Which rock is worn away faster?
The soft rock
提示The one that is easier to erode.
为什么The soft rock below is undercut, leaving the hard rock as an overhang. Eventually the overhang collapses and the waterfall steps back upstream.
- A waterfall keeps retreating upstream over thousands of years. What steep-sided valley does it leave behind?
A gorge
提示Think of a narrow, deep valley with rocky walls.
为什么Each time the overhang collapses the waterfall moves back, and the channel it abandons becomes a gorge.
- On the inside of a meander, the water is slow. What does the river do there?
It deposits sediment, building a slip-off slope
提示Slow water cannot carry as much load.
为什么The sediment piles up into a gently sloping bank of sand and gravel, while the fast outside bend erodes a steep river cliff.
- A meander loop is cut off from the river when the narrow neck between two bends is eroded through. What is the cut-off loop called?
An oxbow lake
提示It is named after a curved part of an old farm yoke.
为什么Deposition seals the ends of the abandoned loop, leaving a curved lake. Over time it can dry out into marshy ground.
- Waves attack a crack in a headland. After the crack widens into a cave, what landform forms if the cave is cut right through?
An arch
提示Think of a rock doorway into the sea.
为什么Waves keep eroding the back of the cave until it breaks through the other side of the headland, leaving an arch.
- When the sea wears down a stack, what small rocky remnant is left, often only visible at low tide?
A stump
提示Think of what is left when a tree is cut down.
为什么The sequence is crack, cave, arch, stack, stump. Waves keep eroding the stack until only a low remnant remains.
- Which type of rock lets very little water soak in, so rainwater runs off into the river and makes a flood more likely?
Impermeable rock
提示Think about the land the rain falls on.
为什么On impermeable rock, water cannot sink in, so it runs over the surface to the river and the river fills faster.
- Cutting down forests on a hillside raises flood risk downstream. Why?
Fewer trees intercept rain and take up water, so more runs quickly to the river
提示Think about what leaves and roots do with rainwater.
为什么Trees catch rain on their leaves and draw water up through their roots. Without them, water reaches the river faster and the peak flow is higher.
1★ KS3-GEOG-RIV-0036
2★ KS3-GEOG-RIV-0037
3★ KS3-GEOG-RIV-0038
4★ KS3-GEOG-RIV-0039
5★ KS3-GEOG-RIV-0040
6★ KS3-GEOG-RIV-0041
7★ KS3-GEOG-RIV-0042
8★ KS3-GEOG-RIV-0043
9★ KS3-GEOG-RIV-0044
10★ KS3-GEOG-RIV-0045