Sedimentary Rocks

Question 1

Weathering

Answer 1

Physical processes like water, the atmosphere and ice working together by physical disintegration and chemical dissolution to break down existing rocks., forming sediment.

Question 2

Sedimentary rocks formation

Answer 2

Physical processes like water, atmosphere and ice working together by physical disintegration and chemical dissolution to break down existing rocks. The products of breakdown(sediment) including resistant minerals, rock fragments and soluble and insoluble materials are transported and deposited.

Burial and compaction of the sediment together with cementation of adjoining grains occur and the 𝐝𝐞𝐧𝐬𝐢𝐭𝐲, 𝐜𝐨𝐡𝐞𝐬𝐢𝐨𝐧 𝐚𝐧𝐝 𝐩𝐨𝐫𝐨𝐬𝐢𝐭𝐲 of the sediment changes as it becomes 𝐥𝐢𝐭𝐡𝐢𝐟𝐢𝐞𝐝 in a process known as diagenesis.

Question 3

Sedimentary rock classes

Answer 3

1. Mechanically formed
2. Organically formed
3. Chemically formed
4. Residual deposits

Question 4

Sedimentary rock is classified?

Answer 4

Classified in terms of 1. Mode of formation

2. Grain size

Question 5

Mechanically formed subdivison

Answer 5

• Rudaceous- Essentially gravels being composed of boulders, cobbles and pebbles(CONGLOMERATE and BRECCIA)
• Arenaceous- Composed essentially of sands to sandstone
• Argillaceous- Composed of finest particles and form MUDSTONES and SHALES

Question 6

Organically formed rocks

Answer 6

Result from the deposition of organic material by organisms and are subdivided on chemical basis.

• Calcareous- Organic deposits consist essentially of calcium carbonate (CALCITE) and are built up largely of parts of shells/skeletons of sea creatures (form SHELLY/CORAL LIMESTONES)
• Carbonaceous- Rich in carbon and form from remains of plants, form deposits of coal. Other deposits form form minute organisms like plankton to form OIL.

Question 7

Chemically formed rocks

Answer 7

Includes deposits that result from the precipitation of material from solutions

• Calcereous- These rocks contain high percentage of calcium carbonate and magnesium carbonate. LIMESTONE is the most abundant, forms by organic or inorganic
• Ferruginous- Form from the precipitation of iron hydroxide. CHAMOSITE (iron silicate)
• Siliceous- Chemically precipitated forms CHERT which is composed of microcrystalline quartz
• Evaporites- Formed from evaporation of salty water. Surface limestone(CALCRETE) forms in arid regions where carbonate rich water is drawn to surface by capillary action then evaporates leaving calcareous deposit