Read the text «The Ocean Floor». Pay attention to the diagram. Fulfill the exercises after the text. (R.P – 8.1.1)

Date: 2015-10-07; view: 510.

Pay attention to the bold terms and expressions in the text

Pay attention to the pronunciation of the geographical terms and especially to the pronunciation of numbers

Vocabulary

COMPREHENSION

PART 1: OCEANIC CRUST

THE RESTLESS CRUST

UNIT 8

97 per cent 7.5 per cent

71 per cent 8.5 per cent

12,400 ft. (feet) ≈ 3 700 m

650 ft. ≈ 200 m

11,500 ft. = 3 450 m

3,300 ft. ≈ 1000 m

10,000 ft. = 3000 m

37,000 mi. (miles) ≈ 60 000 km

35,840 ft. = 10 752 m

3300 ft. - 33 hundred feet

Oceans and their seas hold 97% of all surface water, and cover some 71% of the Earth to an average depth of 12,400 ft. (3700 m). Stripping off this watery sheathwould reveal valleys, plateaus, peaks and plains. We show ten features of the ocean floor.

Continental shelf- a continent's true but submerged and gently sloping rim, descending to an average depth of 650 ft. (200 m). Continental shelves occupy about 7.5% of the ocean floor.

Continental slope- a relatively steep slope descending from the continental shelf. Such slopes occupy about 8.5% of the ocean floor.

Submarine canyon- a deep cleft in the continental slope, cut by turbid river water flowing out to the sea.

Continental rise- a gentle slope below the continental slope.

Submarine plateau- a high seafloor tableland.

Abyssal plain- a sediment-covered deep-sea plain about 11,500-18,000ft (3450-5400 m) below sea level.

Seamount- a submarine volcano 3300ft. (1000 m) or more above its surroundings. Guyotsare flat-topped seamounts that were once volcanic islands.

Spreading ridge- a submarine mountain chain generally 10,000 ft. (3000 m) above the abyssal plain. A huge system of such ridges extends more than 37,000 ft. (60000 m) through the oceans. The Mid-Atlantic Ridge surfaces in places as volcanic islands such as Iceland and Ascension Island.

Trench- a deep, steep-sided troughin an abyssal plain. At 35,840 ft. (10752 m) below sea level (deep enough to drown Mt. Everest). The Pacific's Marianas Trench is the deepest part of any ocean.

Island arc- a curved row of volcanic islands, usually on the continental side of a trench.

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