Earth science 2.3 : Sedimentary Rock
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Transcript of Earth science 2.3 : Sedimentary Rock
SEDIMENTARY ROCK
Earth Science
Chapter 2.3
Objectives:
1. Describe the origin of sedimentary rock.
2. Describe the three main categories of sedimentary rock.
3. Describe three types of sedimentary structure.
Origins of Sedimentary Rock Wind, water, ice, sunlight, and gravity all
cause rock to physically weather into fragments
Through erosion, these rock and mineral fragments, called sediment, are moved from one place to another.
The sediment is deposited in layers, and eventually newer layers cover the older layers.
The most noticeable feature of sedimentary rock is its layers, or strata.
A single, horizontal layer of rock is sometimes visible for many miles.
Composition of Sedimentary rock Sedimentary rock is classified by the way it
forms.
1. Clastic sedimentary rock made of fragments of rocks cemented together
by a mineral such as calcite or quartz. can have coarse-grained, medium-grained, or
fine-grained textures.
Course – grained Fine – grained
ConglomerateSandstone
Shale
Siltstone
2. Chemical sedimentary rock forms from solutions of dissolved mineral and water.
As rainwater slowly makes its way to the ocean, it dissolves some of the rock material it passes through
Some of this dissolved material eventually crystallized and forms the mineral that make up chemical sedimentary rock.
Halite
3. Organic sedimentary rock made up of the skeletons and shells of sea
animals○ These remains collect on the ocean floor and
eventually become cemented together Coal is a type of organic sedimentary rock that is
formed when decomposed plant material is buried beneath sediment and is changed by increasing heat and pressure.
Chalk Coal
Sedimentary Rock Structures
Many features indicate the way sedimentary rock is formedMost important feature is stratification
○ the process in which sedimentary rocks are arranged in layersStrata differ from one another depending on
○ Kind○ Size○ Color
Ripple marksFeatures in which sedimentary rocks sometimes
record the motion of wind and water waves on lakes, oceans, rivers, and sand dunes
Mud cracksStructures that form when fine-grained sediments
at the bottom of a shallow body of water are exposed to the air and dry out.
Even raindrop impressions can be preserved in fine-grained sediments, as small pits with raised rims.