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Sedimentary Rocks  Sedimentary rock is formed by erosion  Sediments are moved from one place.

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Presentation on theme: "Sedimentary Rocks  Sedimentary rock is formed by erosion  Sediments are moved from one place."— Presentation transcript:

1 Sedimentary Rocks  Sedimentary rock is formed by erosion  Sediments are moved from one place to another  Sediments are deposited in layers, with the older ones on the bottom  The layers become compacted and cemented together

2 Sedimentary Rock  Sedimentary Rocks are formed at or near the Earth’s surface  No heat and pressure involved  Strata – layers of rock  Stratification – the process in which sedimentary rocks are arranged in layers

3 Sediments -pieces of material left by: *wind*ice*chemical precipitation *water *gravity Step 1: WEATHERING Chemical- minerals are chemically broken down

4 * Physical – minerals remain chemically unchanged

5 Step 2: EROSION * transporting weathered materials to another location * Wind, water, gravity and glaciers transport

6 Step 3: DEPOSITION * sediments are deposited and sorted

7 Step 4: BURIAL * deposited into depressions called “sedimentary basins” * the deeper it gets, the more pressure on it til…… 2 ROCK BURIAL

8 Step 5 : LITHIFICATION (FYI – lithos: Greek for stone) * physical and chemical process that changes it to sedimentary rock 1 st Compaction 2 nd Cementation & Solidification new minerals precipitatemore of the same type around existing ones crystallize around existing ones

9 FEATURES OF SEDIMENTARY ROCKS BEDDING – *horizontal layers *if sorted, graded bedding CROSS-BEDDING - *inclined layers move forward like sand dunes

10 RIPPLE MARKS * when sediment is moved into small ridges by wind or wave action * back & forth waves yield symmetrical waves * currents, (like in rivers) asymmetrical waves Sand dune – ripple marks from wind

11 Asymmetrical ripple marks

12 FOSSILS *animals die, buried, lithified * some plants replaced by other minerals * shells, bones, etc. could leave impressions

13 CONCRETIONS * lumps of fine grained silica * called chert *also called nodules CHERT

14 MUD CRACKS *wet clay dries and contracts * cracks later fill with sediment

15 TYPES OF SEDIMENTARY ROCKS 1.CLASTIC formed by lithifications CoarseMediumFine gravelsandsilt & mud some rockssandstonesiltstone conlglomeratesmudstone POROSITY * percent of open space between grains of sand *good reservoirs for oil, natural gas, and H 2 O * permeable if water can pass through

16 Porous Rock

17 2. CHEMICAL a. rocks formed by evaporation - called evaporites ex: calcite, halite & gypsum S CALCITE DEAD SEA SALT

18 b. organic sedimentary rock -formed from the remains of living things - most abundant is limestone (mostly calcite) CaCO 3 from shells if shells are high in silica, they form siliceous ooze - Coal – from remains of plant material…almost entirely carbon CALCAREOUS OOZE Siliceous ooze


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