Read the following phrases, write down the word. Read the word and find sentences with this word.
UNIT 6 SEDIMENTARY ROCKS 1. COMPREHENSION 1.1 Vocabulary Give the translation of the following terms based on the definition TERM DEFINITION TRANSLATION skin a thin crust of smth. scrap fragment or small pieces deposit any earth material accumulated by water / ice, etc. remains a trace of smth. (animal – fossils) bed (stratum) a layer of rock to pile to accumulate / collect in a mass to deposit to settle down to pack to become firmly pressed to convert to change from one form to another to consolidate to harden to cement to bond firmly with the help of some material to abrade to wear away by erosion to compact to pack closely to accumulate to gather in a mass
Read the following word formations and remember their pronunciation
Tion
Verb
compact
cement
accumulate
sediment
consolidate
abrade
Noun
compaction
cementation
accumulation
sedimentation
consolidation
abrasion
1.2 Read the text and fulfill the after reading exercises (R.P – 6.1) ROCKS FROM SEDIMENTS
Sediment or sedimentary rock covers most ocean floor and three-quarters of the land. On land this skin is usually a few miles thick; but layers up to 19mi (30 km) thick collect on offshore basins. Most sedimentary rock comes from scraps of older (igneous or other) rocks eroded from the land, carried into lakes or seas by rivers, deposited, and then consolidated in a solid mass. When parent rock breaks up its minerals behave in different ways. Some of the silicates (the main mineral ingredients of igneous rocks) dissolve; others- quartz, for one- endures; and weathering creates new minerals- especially the clays that bulk large in most sedimentary rock. Besides the clastic sedimentary rocks (rocks made from fragments) others come from chemical precipitates or the remains of living things.
Processes converting sediment to rock are known as diagenesis . Two main processes occur. As sediments pile up their pressure squeezes water from the sediments below and packs their particles together. Then, some minerals laid down between grains cement a mass of sediment together.
Changes converting sediment to rock leave traces in the finished product. Transportation of eroded sediments abrades and rounds their particles, sorts these by density or size, “rots” unstable minerals, and concentrates resistant minerals, including diamonds and gold.
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Deposition lays down sediments in broadly horizontal sheets called beds or strata, each separated from the next in the pile by a division called a bedding plane. Beds with ripple marks reveal ancient currents. Graded bedding (beds with grain size graded vertically) may hint at turbidity currents – sediment rich water sliding soupily down a continental slope. Cross bedding (sands laid down at an angle between two bedding planes) show features such as old dunes and sand-bars.
(David Lambert “The Field Guide to Geology” 1988, Cambridge University Press)
Fig. 29 Breccia
EXERCISES
2.1 Match the terms with the definition
| 1. weathering | a. decrease in pore space of a sediment and reduction in volume / thickness |
| 2. deposition | b. a mineral between the sediment grains, forming an integral part of the rock |
| 3. diagenesis | c. mechanical wearing down of rock surfaces by friction of rock particles |
| 4. bedding plane | d. the sum of all processes that contribute mass to particles |
| 5. cross bedding | e. process of depositing sediments |
| 6. graded bedding | f. destructive natural process by which rocks are changed |
| 7. sedimentary rocks | g. movement of particles by air/water/ice or gravity |
| 8. sedimentation | h. process by which clastic sediments are converted into sedimentary rock by precipitation of a cement |
| 9. transportation | i. beds with grain size graded vertically |
| 10. cementation | j. process to lay sediments in wide horizontal beds |
| 11. cement | k. a division separating one bed from another |
| 12. abrasion | l. sands lay down at an angle between two bedding planes |
| 13. compaction | m. rocks formed by the consolidation of sediments settled out of water/ice/air and accumulated on the Earth’s surface |
| 14. accumulation | n. process converting or changing sedimentary rocks |
Read the following phrases, write down the word. Read the word and find sentences with this word.
1. to press / pack closely 12. to bond firmly together
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2. fragments / small pieces 13. a thin crust of smth.
3. accumulate / collect in a mass
4. to change from one form to another
5. to make solid / to harden
6. to put / set down
7. to wear away by erosion
8. a trace of smth.
9. to add to smth.
10.a layer / stratum of rock
11.to become firmly pressed
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