Summary

This document describes the different types of sedimentary rocks, including clastic, chemical, and organic. It covers their formation and features, along with practice questions about classifying and comparing these rock types.

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SES4U​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Name: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Date: Sedimentary Rocks By the end of this lesson, I will be able...

SES4U​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Name: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Date: Sedimentary Rocks By the end of this lesson, I will be able to classify different types of sedimentary rocks based on their physical properties and formation Sediments are smaller pieces of pre-existing rock. There are three distinct types of sedimentary rocks: ​ Clastic Sedimentary Rock ○​ These are formed from abundant deposits of loose sediment. ○​ Existing rock is weathered (broken down into smaller pieces called sediments). ○​ These sediments are then eroded (transported to new locations). ○​ Eventually these sediments are deposited, buried, and compacted (squeezed together). ○​ When buried 3 to 4 km deep, the increased pressure and temperature begin chemical changes that result in mineral growth that binds the sediments together into solid rock. This is known as cementation. ○​ Breccia, conglomerate, sandstone, siltstone, and shale are all clastic rocks. ​ Chemical Sedimentary Rocks ○​ These are formed when dissolved chemicals precipitate out of water. ○​ These usually occur in arid areas. Why? ○​ Iron ore, chert, some dolomites, rock salt and some limestones are all chemical. SES4U​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Name: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Date: ​ Organic Sedimentary Rock (Biogenic) ○​ These are formed from the accumulation of plant or animal debris. ○​ This debris contains calcium that piles up on the floor of water bodies over years. ○​ Coal, amber*, some dolomites, and some limestones are organic. Features This type of rock formation leads to horizontal layering or bedding. The layers are known as strata. This layering aspect provides geological snapshots of Earth’s past surfaces which is a valuable tool in reconstructing Earth’s past. Oil, natural gas, coal, and uranium, our major energy resources, are formed in, and come from sedimentary rocks. Sand and gravel for construction come from sediment. Sandstone and limestone are used for building stone. Rock gypsum is used to make plaster. Limestone is used to make cement. Sedimentary rocks will also often contain fossils, the impression of living organisms buried underneath layers of sediment. Nodules, Concretions, and Geodes Limestones and chalk often contain hard lumps of fine-grained silica called nodules. Whitish, brown, or gray nodules are called chert; darker varieties are called flint. Stone age humans made weapons and tools from chert and flint as they were easy to sharpen due to the fine-grained texture. Round solid masses of calcium carbonate are known as concretions and often occur in layers of shale. Both nodules and concretions form when minerals in a solution precipitate around a shell fragment or other impurity in the clay sediments. Limestones sometimes contain spheres of silica rock, known as geodes. The interior may be lined or completely filled with crystals - typically quartz and calcite. It is hypothesized that geodes form when groundwater creates cavities in limestone. Minerals in the groundwater then concentrate in the cavity, where they grow as crystals. SES4U​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Name: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Date: Practice! 1.​ From where a stream runs into a lake and out into the middle of the lake, in what order would you most likely find the three basic types of clastic sedimentary rock (conglomerate, shale, sandstone)? 2.​ Compare and contrast sedimentary rocks of chemical origin and organic origin. How are they similar? How are they different? 3.​ Which physical feature is common in every type of sedimentary rock?

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