S.M.S. Toti Dal Monte

S.M.S. TOTI DAL MONTE

MOGLIANO VENETO

A.S. 2007/2008

PROGETTO COMENIUS – LINK

“CONTINENTAL DRIFT”

Classe 3^ L

Insegnanti: Sandra Zanoni (Scienze M.C.F.N.)

Lilia Biscuola (Inglese)

INTRODUCTION

This is a physical map of the world.

How many continents are there? Name them.

………………………………………………………………………………………….………………………………………………………………………………………….………………………………………………………………………………………….

ACTIVITY 1

Put the correct name of the continent in each blank.

QUESTIONS:

Do you think the continents always looked as they do on the map?

……………………………………………………………………………………………………………………………………………………………………………………………………………………

Do you think they have changed shape or location throughout Earth’s history?

………………………………………………………………………………………….………………………………………………………………………………………….

• Now look at the animations:

Were you right or wrong?

………………………………………………………………………………………….………………………………………………………………………………………….

What do you think it is about?

………………………………………………………………………………………….………………………………………………………………………………………….

Can you describe what you have just seen?

………………………………………………………………………………………….………………………………………………………………………………………….

• Read the following text:

CONTINENTAL DRIFT

In 1915, the German geologist and meteorologist Alfred Wegener first proposed the theory of continental drift, which states that parts of the Earth’s crust slowly drift. He hypothesized that there was a gigantic supercontinent 225 million years ago, which he named Pangaea, meaning “All earth/land”. This huge supercontinent was surrounded by one gigantic ocean called Panthalassa.

About 200 million years ago the supercontinent Pangaea began to break up. About 180 million years ago Pangaea broke into two new continents Laurasia and Gondwanaland. The huge ocean of Panthalassa remained but the Atlantic Ocean was going to be born soon with the splitting of North America from the Eurasian Plate.

The fit of the continents and the distribution of fossils and rocks supported Wegener’s theory. For example, rock sequences in South America, Africa, India, Antarctica and Australia show remarkable similarities in age and mineral composition. Wegener proposed that rock sequences were made when all the continents were part of Pangaea. Thus, they formed in a smaller contiguous area that was later broken and drifted apart. (see Activity 2)

Fossils of the same species (Mesosaurus,Cynognathus, Lystrosaurus –reptiles- and Glossopteris -a fern) were found on several different continents, too. Wegener proposed that the species dispersed when the continents were connected. For example Glossopteris, a fern, was found on the continent of South America, Africa, India and Australia. (see Activity 3)

About 135 million years ago Laurasia was still moving, and as it moved it broke up into the continents of North America, Europe and Asia (Eurasian plate). Gondwanaland also continued to spread apart and it broke up into the continents of Africa, Antarctica, Australia, South America, and the subcontinent of India. Arabia started to separate from Africa as the Red Sea opened up. The Atlantic, Indian, Arctic, and Pacific Oceans were all beginning to take shape as the continents moved toward their present positions.

Notice the position of the Indian Subcontinent today. It moved hundreds of miles in 135 million years at a great speed. India crashed into the Eurasian continent with such a speed and force that it created the tallest mountain range on Earth, the Himalayas!

The continents are still moving today making the Atlantic Ocean larger and the Pacific Ocean smaller.

GLOSSARY

a. Contiguous = next in order = contiguo, vicino

a.+ n. Continental drift = deriva dei continenti

v. To drift = to move passively = spostarsi lentamente

n. Fern = a plant = felce

n. Fit = matching = adattamento

a. Huge = enormous = enorme

n. Splitting = separation = separazione

v. To spread (apart) = to cover larger surface = espandersi

v. To state = to express = affermare

v. To surround = tobe all round = circondare

prep. Toward/Towards = in the direction of = verso

• EXERCISES

1) Write if these sentences are true (T) or false (F). Correct the false ones.

• Laurasia and Gondwanaland were giant continents
• Pangaea began to break up 180 million years ago
• The Atlantic Ocean was born by the break of America and Europe
• Fossils did not support Wegener’s theory
• Glossopteris was found in South Africa, India and Australia

2) Choose the right answer.

1. Wegener hypothesized that 200 million years ago:

• There were two gigantic supercontinents
• The continents were just like today
• There was a gigantic supercontinent

2. What did Laurasia break up into?

• The Eurasian continent
• Europe and Asia
• North America and the Eurasian continent

3. What did Gondwanaland break up into?

• Africa and Antarctica
• India and Asia
• Australia, Africa, India, Antarctica and South America

4. How were the Himalayas created?

• The Eurasian continent crashed into India
• India crashed into the Eurasian continent
• India moved towards Australia

• ACTIVITY 2

Materials:

- shapes of the continents

- glue

- cardboard

Procedure:

Here are the shapes of the continents of the Southern hemisphere. Try to piece them together as Gondwanaland. When you are sure each piece is where you want, glue them on the cardboard. Compare your version of Gondwanaland with the picture of what the scientists believe Gondwanaland looked like.

• ACTIVITY 3

Materials:

-your version of Gondwanaland

-pictures of fossil organisms

-glue

-data chart

Procedure:

Using the data chart below, place a picture of each representative fossil on the appropriate continent.

Data chart

Mesosaurus: freshwater swimming reptile found in Brazil and in Africa.

Cynognathus: large land reptile (9 feet long) found in Argentina, Southern Africa, India and China.

Glossopteris: a seed fern found in South America, Africa, Madagascar, India, Antarctica and Australia.

Lystrosaurus: a herbivorous reptile with a very distinctive skull shape, found in Africa, India, Antarctica, Indochina, Western and Central China.

Remember: China and Indochina are not included in Gondwanaland map!

GLOSSARY

n. Freshwater = water that is not salty = acqua dolce

n. Skull = part of skeleton corresponding to head = cranio

Now compare your reconstruction with the map of fossil distribution made by Wegener.

QUESTIONS

Could these plants/animals have crossed the ocean?

…………………………………………………………………………………………………………………………………………………………………………………….

Scientists have evidenced that Glossopteris was found in what is now India, Antarctica, Australia, and Madagascar. What does this tell you about Glossopteris? What does it tell you about the climate and environment of Gondwanaland?

………………………………………………………………………………………….………………………………………………………………………………………….

Mesosaurus is a freshwater swimming reptile found in Brazil and in Africa. Do you think it could have crossed the Atlantic Ocean?

……………………………………………………………………………………….…………………………………………………………………………………………….

• Read the following text:

Wegener’s model was not accepted by all geologists, because he could not find an adequate mechanism for moving the continents; in fact he could not explain what kind of forces could be strong enough to move such large masses of solid rock over such great distances.

A mechanism to move continents was proposed by Arthur Holmes in 1928; later, during 1940s and 1950s, great advances were made in the knowledge of sea floor and in the properties of rocks. These studies provided new evidences to support continental drift.

In order to understand how continents can move, we need to know what is the inner structure of the Earth.

Layers of the Earth

The Earth is divided into three chemical layers: the core, the mantle and the crust. The core is composed of mostly iron and nickel and remains very hot. The core is divided into two layers: a solid inner core and a liquid outer core. The middle layer of the Earth, the mantle, is made of minerals rich in the elements iron, magnesium, silicon, and oxygen. The crust is rich in the elements oxygen and silicon with lesser amounts of aluminium, iron, magnesium, calcium, potassium, and sodium. There are two types of crust.

Oceanic crust is made of relatively dense rock called basalt. Continental crust is made of lower density rocks, such as granite.

The outermost layers of the Earth can be divided by their physical properties into lithosphere and asthenosphere. The lithosphere (from the Greek, lithos, stone) is the rigid outermost layer made of crust and uppermost mantle. The asthenosphere (from the Greek, asthenos, devoidof force) is part of the mantle that flows, a characteristic called plastic behaviour. It might seem strange that a solid material can flow. A good example of a solid that flows, or of plastic behaviour, is the movement of toothpaste in a tube.

GLOSSARY

a. Devoid (of) = privo (di)

n. Evidence = proof = prova

v. To flow = to move continuously = scorrere

n. Iron = silver-white metal = ferro

It might seem = potrebbe sembrare

a. Outermost = external = più esterno

a. + n. Plastic behaviour = comportamento plastico

n. + n. Sea floor = bottom of the sea = fondale

a. Uppermost = at the top = superiore

• ACTIVITY 4

Match the name of each layer with the proper location. Specify if each layer is solid or liquid.

• ACTIVITY 5

• Read the following text:

HOW CAN CONTINENTS MOVE?

The inner part of the Earth is very hot; this explains why the rocks of asthenosphere have a plastic behaviour, i.e. they can flow. Many geologists think that in the mantle there are very slow convection currents (only few cm per year): the deepest material, that is very hot, rises, becomes cool, flows laterally and then falls. (see Activity 6).

The rigid lithosphere seems to float over these convection currents.

Geologists have known for over a century that there is a ridge in the middle of the Atlantic Ocean (Mid-Atlantic Ridge); itis an area of earthquakes and the rocks near it are younger than the other rocks of the ocean floor. Moreover, they are much younger than the rocks of the continents. Thus, in 1962 the geologist Harry Hass proposed that new ocean floor is formed at the top of Mid-Ocean ridges. The ocean floor, and the rocks beneath it, are produced by magma that rises from deeper levels. (see Activity 7)

But, if new oceanic lithosphere is created at Mid-Ocean ridges, where does it go?

Convection cells in the mantle help carry the lithosphere away from the ridge. The lithosphere arrives at the edge of a continent, where it is subducted, that is it sinks into the asthenosphere. Thus, oceanic lithosphere is created at Mid-Oceanic ridges and consumed at subduction zones, areas where the lithosphere sinks into the asthenosphere. (see Activity 8)

GLOSSARY

p. Beneath = under = sotto

v. To float = galleggiare

n. Ridge = dorsale

v. To sink = to disappear below the surface of a mass of water = affondare

v. To be subducted = essere subdotto (affondare sotto il mantello)

• ACTIVITY 6

Materials:

-a big beaker

-alcohol burner

-tripod and wire gauze

-cold water

-flour

-a tablespoon

Procedure:

-Half fill the beaker with cold water.

-Spread half tablespoon of flour over the water surface.

-Put the beaker over the tripod.

-Light the alcohol burner.

-Look at the water surface for some minutes: what can you see?

You can see circular motions inside the water. In fact the flame heats the water at the bottom of the beaker; hot water is lighter than cold water, so it rises and moves on the surface; cold water, that is heavier, falls, then moves on the bottom, heats and rises again. In this way circular motions, called convection cells, are formed.

The material of asthenosphere acts just like water.

GLOSSARY

n. Tripod and wire gauze = treppiede e reticella spargifiamma

n. Flour = farina

• ACTIVITY 7

Materials:

-a wax candle

-a small beaker

-alcohol burner

-tripod and wire gauze

Procedure:

-Break the candle into small pieces.

-Put the pieces in the beaker.

-Light the alcohol burner.

-When the wax is melted, turn off the alcohol burner.

-Pour some cold water over the melted wax.

-Light the burner again: what can you see?

-When the wax is melted again, turn off the burner.

When the wax is very hot, it changes into gas and produces bubbles. They quickly go up, cross the wax crust and create “volcanoes”.

The lithosphere acts like wax: when the hot material of the asthenosphere rises, it swells and breaks creating new volcanoes. The highest volcanoes are at the bottom of the oceans, where there are the Mid-Ocean ridges.

GLOSSARY

n. Wax = cera

v. To melt = become liquefied by heat = sciogliere

v. To pour = versare

v. To swell = gonfiarsi

• ACTIVITY 8

Materials:

-two beakers

-a bowl

-mashed potatoes

-flour

-red food dye

-polystyrene tray

-two square cardboards

-scissors

Procedure:

-Put three tablespoons of mashed potatoes in each beaker.

-Add some red food dye to one mixture and a tablespoon of flour to the other one; mix.

-Cut a fissure in the middle of the polystyrene tray.

-Pour some mixture of mashed potatoes and flour on a sector of the tray and some coloured mashed potatoes on the other sector.

-With the cardboard, push the mixtures one against the other. What can you observe?

The mashed potatoes with flour fall into the fissure and the coloured mixture slides over it and creates a “mountain chain”. In fact the mixture with the flour is heavier than the other, and sinks into the coloured one, which is lighter.

The same happens in the ocean floor: new ocean floor is formed at the mid –ocean ridge, it becomes cold and heavier and sinks into the mantle, creating the oceanic trench.

GLOSSARY

n. Bowl = round container = scodella

a. + n. Mashed potatoes = purè

n. +n. (Food) dye = substance used to change the colour of food = colorante per

alimenti

n.+ n. Polystyrene tray = vassoio di polistirolo

n. Trench = fossa

PROGETTO COMENIUS LINK

1)Match each definition with the correct term:

2)Word search: find the most used words that you learnt (there are 12 words):

1) ………………………………

2) ………………………………

3) ………………………………

4) ………………………………

5) ………………………………

6) ………………………………

7) ……………………………....

8) ………………………………

9) ……………………….……...

10)………………………………

11)………………………………

12)……………………………….

3) Fill in the gaps. Choose the correct word in the Word Bank:

In 1915 ...... first proposed the theory of ...... He hypothesized that there was a gigantic supercontinent 200 million years ago (...... ) surrounded by a gigantic ocean (...... ). The fit of the continents and the distribution of ...... and rocks supported his theory. The continents are still moving today.

Wegener’s model was not accepted by all geologists, because he could not explain what kind of ...... could be strong enough to move such large masses of solid rock over such great ......

Some years later, geologists hypothesized that in the ...... of the Earth there are very slow ...... : the deepest material, that is very hot, ...... , becomes cool, flows laterally and then ...... The lithosphere seems to float over these convection currents.

In 1962 ...... proposed that new ocean floor is formed at the top of ...... Convection cells in the mantle help carry the ...... away from the ridge: the lithosphere arrives at the edge of the continents where it is ...... , that is it sinks into the ......

1