Стр.146-147 Across the curriculum ГДЗ Комарова Ларионова 9 класс
9 Geography Natural wonders of the world 1 Match the words with the pictures. 1 volcanic crater 2 waterfall 3 cave 4 glacier 5 canyon 6 sea cliffs 7 reef 8 lava flow Underground wonders (limestone caves) 2 Read the text and answer the questions.
Приведем выдержку из задания из учебника Комарова, Ларионова 9 класс, Русское слово:
9 Geography
Natural wonders of the world
1 Match the words with the pictures.
1 volcanic crater
2 waterfall
3 cave
4 glacier
5 canyon
6 sea cliffs
7 reef
8 lava flow
Underground wonders (limestone caves)
2 Read the text and answer the questions.
1 Is limestone an igneous, metamorphic or sedimentary rock?
2 What is the chemical composition of limestone?
3 How did limestone rocks form?
4 Why can water erode limestone?
5 What formations are the result of erosion in limestone?
Limestone and chemical erosion
Limestone is a hard. grey, sedimentary rock which formed millions of years ago in areas where there used to be tropical seas. Small animals or plants containing calcium carbonate (CaC03) lived in those tropical seas and when they died, their remains accumulated into layers of calcium carbonate. With pressure and heat over millions of years, limestone rocks began to form.
Water enters cracks in the limestone rock and gradually erodes the cracks until they become very large. When rivers reach an area of limestone, they often disappear because the water travels along tunnels which have become so large that the river travels underground.
The underground rivers can erode the rock to form enormous cave systems with large underground lakes and with tunnels sometimes hundreds of kilometres long. The formation of caves means that impressive stalactites, stalagmites and pillars often form.
3 Read the text again and name parts a-e of the diagram. Use the words in the box.
4 Read the text and put the paragraphs in the correct order.
How stalactites and stalagmites form
a Very often the place on the cave floor where the drop of water lands is where a twin structure begins to grow up.
b Little by little a hollow stalactite grows downwards as water drips out of the cave ceiling depositing calcium carbonate.
c Stalagmites form when calcium carbonate is deposited on the cave floor and the deposit grows upwards and sometimes even joins the stalactite above, forming a pillar.
d Limestone is not very soluble in water, but when rainwater moves through calcium carbonate, it dissolves carbon dioxide and minerals from the limestone like this: H2O+C02+CaCO2 = Ca(HCO3)2 Limestone is carried in water as calcium bicarbonate Ca(HCO3)2 and it moves through cracks in the rock.
e When the water travelling through the rock reaches a cave, some of the calcium bicarbonate transforms back into calcium carbonate. It comes out of solution and is deposited on the roof of the cave.
Project
Either find out about limestone scenery in your country or in another country or carry out some research on other types of erosion which have formed natural wonders.
Plan
Decide what natural feature you would like to find out more about. For example, the Kapova cave, in the Urals.
Research
Find information about the rock formations and how they were eroded. Do an Internet search with the name and find a suitable web page.
Prepare
Copy and complete the table with information about the rock formations.
Place name
Location
How were the rocks formed?
How were the rocks eroded?
Other information
Present your material
Present your completed project to your classmates and teacher.