1970-02-01 — Page 15

FEB 1970

T*E* 真三第張四第5日五十月二十年西已愿厦 WAH KIU YAT PO

報日僑單 CITY HALL

日期星

日一月二年〇七九一膳公年九十五國民華中

DRIFT MINING

(接第四張第二頁)

АДВ

O英文中學會考試題預習專欄

堅道 文書院主編

十三)

地理科

GEOGRAPHY (13)

(1) Outlize the factors which influence mining

activities,

(ii) Distinguish surfeds and underground mining.

What are their advantages and disadvantages? (i) in all mining sotivities, vaere are several

geographical and economic factors which help to decide whether the ore-body is worth the expenses inourred in the exploitation. (1) Bise of the eza-body

Low quality minerals are mined if the ore-body is large, 1.0, the mineral reserve is great. Large ore-body facilitates the use of machineries and the cost of mining. eas thus be lowered. High grade ores are not mined if the total mineral réserves are small. At the present level of technology, copper ore with a metal opstant of as low. as 0.7% is mined.

Acosusibility of the mins

16 particularly important when is carried out in remote and sparsely populated areas. Unless the ore is processed near the mine, the movement. of the ore to the dressing plant will be dependent on the transport facilities available.

(III) Thickness and continuity of sean

This factor affects the mining of soal mainlys for mining of coal by shaft sethod, the thickness of the seam should be over 7 fest thick and the seam should not be disturbed by folding or faulting. (IV) Labour

Since metalliferous mining 18 mostly earried on in areas by no means densely populated areas except in South-east Asia, it can not be said that the supply of Labour is not a matter of serious consideration. Special allowance makes. white labour expensive iz zöst cases and native Labour is cheap, but is often inefficient.

(V) Price of the ove

If the price of a certain metal goon up tremendously in the world market then low grade ore in a remote corner of the world would be exploited.

(VI) Capital

Kost forms of mining to-day require a heavy capital investment in the pit and in various facilities. Therefore an ore-body which lies near an economically advanced sation would receive more attention than a high grade ore that lies in a less developed country.

(VII) Political consideration and government

interference

Kinerala of military importance are

minod when they are seeded portas considering their qualities, e.g. Germany developed her own low grade iron ore during the War; Romania's oil, Japan's copper and Canada's uranium are also examples that illustrate this point. vary well.

Government may interfere, when for imple, improper disposal of rook waste uncontrolled mining causing landslide may affect the oultivated land down the hill #lops such as in Ma On Shan, or contaminated water from the mine is liable to infiltrate into a reservoir as in the case of the wolfram mine in Needle Hill.

Most of the mineral output of the world 18 obtained by either surface or underground mining methode, Surfeos mining embraces. several types.⠀

(1) PLACER MINING: One of the mimplent typos.

of surface mining is the hand-panning of stream gravels (placar deposits) for gold, diamonds, and the platinum sotals. This: method was quite important in the 19th century and it is mostly osrried out along river beds and is used widely in the mining of tin in Malaya. Such primitive method is now being replaced by the suction er conveyor dredging of minerals in placer. deposits.

(11) OPEN-CAST KIFING: this method includes

many sub-types but the most important one is strip mining. It is practised if the ore Lies near the surface of the earth's crust. The over-burden 18 removed by machineries and such mathod is cheap and Véry convenient. However this method sannot be practised in areas where there are population concentration and it might take up some valuable agricultural lands, (III) DEILS (ADET) MINING; When coal seam or

other mineral deposits are exposed by river erosion, the drift method of mining is usually practised. Tunnels are constructed into the sides of the v#LLOY and the mineral oren are zemoved in the

RIVER

Underground' minang

(IV) SHAFT MINING: It as the most common type of underground mining; tunnels are sink: into the ore-body and the mineral 20 transported up the shaft by conveyor belts or elevators to the surface where they are processed or carried to the dressing plante by means of light railways.

MINING

SHAFT

SLOPE MINING: When the coal seam or the ore-body is dipping at an angle towards the ground, the shaft method he not quite suitable. Another method known a slope mining replaces shaft mining, the only nignifionatu difference between shaft and plope mining lies in the fact that the Isänel-in the latter method. is not horisontal nor vertical but follows more or less the dipping angle of the ore body

SLOPE

SURFACE MIXING

MINING

ADVANTAGES

Heavy machineries can be utilised thui lowering the cost of mining.

2. Unaffected by poor

weather conditions.

3. Low labour and

maintenance costs.

4. Low grade ores can be

- mined by this method.

SURFACE MINING

UNDERGROUND MINING

Deep-seated ore bödieS can be exploited aven they may be disturbed by earth movements.

Takes up less surface

area than surface mining and it can be carried but underneath large urban areas if supports are properly installed.

DISADVANTAGES

1. Takes up a large

surface area thus hindering other. economio activities,

2. If the over-burden

is thick, surface mining would be very costly,

3

UNDERGROUND MINING

Affected by weather

condi tioss

High maintenance cost. (a.g, the provision of lighting, ventilation and communication network- beneath the ground level.)

Only high grade ores can withstand the high cost incurred in this method of mining.

B) For what reasons has aluminium suddenly become

such an important metal and why is the production of this metal so often widely distant from the Bources of the ore?

Але

The discovery of aluminium and the use of it 18 of recent date. There has been an extraordinary! increase in the world's production from less than of a million ton in 1930 to nearly 4 million in 1962. This results from several special qualities including its lightness, its strength compared with its weight, especially when alloyed with small quantities of other metals, the same with which if ite alloy can be worked, its ability to resiat corrosion and lastly, its high electrical conductivity. Thus it is principally used in the making of transport vehjuclas, such as aircrafte motor engines and ships, (the super-structure of the recently launched Q.E. 2-18 made of aluminium) as well as in long distance electricity transmission

文中學會考試題預習專欄

生物科 (十三)

莫愛桐•

(4)本程(5)次生木質部(6)次生靱皮部(2)初生本部( ◎次生木部或次生靱皮部是由何者分生成

的形成層)生長點 (6)表皮(d)薄壁組織

中盤

原分生組織和物生分生組織位。 心维管束形成層如藝和根工尖端 (4)木裕成層

下圖是雙子葉植物根之切面.

4.寫出標線所指者部錯猾名稱:

B寫出下列號碼所屬部位之功用:

2.6

7C

8.C

C. 下列號碼所屬部位完屬何種組織?

下列號碼所屬部位含有那些细胞,

96

Lines in domestic equipaenta such as kettle,

* kachines, sauos pans eto,

The world's important producers of bauzite Core of aluminium) include Jamaion († of the world's total), U.S.S.R., the Guianas, France and the State of Arkansas in the United States. The extraction of aluminium from baurite is still not easy since a large amount of electricity in required. (for smelting 1 ton of aluminium, 18,000 Kwh of electricity supply is needed) In nearly every case, aluminium worka are situated where electricity can be obtained cheaply, usually from water power. In those Less developed tropical nations, water power is not well developed, so the biggest producers are the leading industrial nations of the world 1.0. U.S.A. (Tennessee Valley, Oregon, Washington), U.S.S.R., Canada, and to a lesser extent, several European countries. such as France, Norway, Sweden, and West Germany ANSWERS TO LAST WEEK:# MULTIPLE-CHOICE EXERCISE

1. (b) 2. (a) 6. (b) 7. (b)

3.

• (0)

8. (n)

QUESTIONS FOR NEXT WEEK:

4. (8) 5. (0) 9. (b) 10, (a)

(1) Write briefly on the formation of oil and

explain why oil is found only in sedimentary FOOK,

(11) Account for the fact that the Furopean

countries are the world's major oil importers, B) Write a concise socount on the formation of coal

and attempt a olemuifiontion of coal according to their carbon content.

C) Outline and discuss the factors which explain the absence of large water power plants in South-east Asia even though there are large potentials.

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