Isostasy

3.3 SCANNING- Earth’s building blocks

You are looking for specific information. Don’t read every word. Run your eye down the text and stop when you find the relevant (важный; существенный) words. You have 3-4 minutes.

1. building blocks-

2. abundance of elements-

3. elements-

4. silicate-

5. crystal-

6. mineral identification-

Earth’s building blocks are elements and minerals of our planet. Of 92 naturally occurring elements, eight account for 98% of the weight of the Earth’s crust – the rocky layer that scientists know best. Nearly 3/4 of its weight lies in two non-metals – oxygen and silicon; most of the rest consists of the six metals-aluminum, iron, calcium, sodium, potassium and magnesium.

Within the crust most elements occur as minerals- natural substances that differ chemically and have distinct atomic structures. The Earth’s crust holds about 2000 kinds of minerals. A few (including gold) occur as just one element; most comprise two or more elements chemically joined as compounds.

Silicates (minerals containing silicon and oxygen) are the most abundant minerals in crust and mantle, which make up 4/5 of our planet’s volume.

Most minerals formed from fluids that solidified – a process that arranged their atoms geometrically producing crystals. Scientists identify six crystal systems based on axes-imaginary lines passing through the middle of a crystal. Each system yields crystals with distinctive symmetry. Within each system, each mineral crystal grows in a special shape or habit, though this can be modified by temperature, pressure and impurities.

Traditional tests identify by hardness, color, streak (color of the powered mineral), luster, specific gravity, cleavage, fracture, form, tenacity (resistance to bending, breaking and other forces), odor, taste and feel.

(Lambert “The Field Guide to Geology” 1988, Cambridge University Press)

Fig. 10. Relative abundance of elements in whole Earth

Fig. 11. Relative abundance of elements in Earth’s crust

4. Listening comprehension

4.1 You will hear a lecture. After the lecture you will hear some statements. The lecture and questions will be spoken just one time. When you hear a statement, read the three possible answers, and decide which one would be the best answer to the statement you have heard.

1. The crystal rind is covered by

A. condensed atmosphere components

B. volatile atmosphere components

C. ocean volatile components

2. The mantle lies under

A. oxide rich shells

B. rocky exterior

C. concentric shells

3. They are

A. constructing blocks

B. constructing rocks

C. constructing layers

4. The main factor is

A. sunlight only

B. the Earth itself

C. physicochemical evolution

5. The following systems

A. protection

B. interconnected

C. biological

4.2 You will hear part of a radio report about the earth as a planet of our solar system. For statements 6- 15, complete the notes that summarize what the speaker says. You will need to write a word or a short phrase in each box.

Earth is a		6
The Earth is the third planet to		7
The planets don’t fly into space because of		8
Life on Earth is due to		9
Each rotation produces		10
The Moon completes		11
while Earth completes		12
This is an Earth’s		13
The Earth is separated from the other bodies by		14
So, the solar system comprises		15