Sedimentary rocks Flashcards
What is a sediment?
Loose pieces of rocks, minerals or organic materials that are broken down from natural process, volcano wind etc
What are sedimentary rocks formed by?
Formed by rock pieces or organic matter being pressed together or chemical precipitation.
Weathring erosion and deposition
Characteristics of sedimentary rocks are…
The source of the sediment( source of how the rock broke down, this also makes up the composition whether its physically broke down or chemically altered
The way the sediment was moved
The conditions of where the sediment was deposited
Formation of sed rocks
2 main ways to convert loose sediment to the rock
compaction- sediment is squeezed and is reduce by weight and pressure
cementation- sediments are glued together by minerals that are deposited by water
Clastic sed rocks are..
Small compacted together, made from pieces of preexisting rocks that are compacted or cemented together after being pushed from their source by water wind or ice.
Clastic sed rocks are classified by the size of sediments they contain Ex
a- conglomerate, rounded pebble size
b-breccia large pieces help together
c- sandstone, small mineral grains
d- shale, fine grained
Characteristics of prexisting (clastic) sediments
They transported by 4 main agents water ice wind and gravity.
sorting- air or water seperating seds according to size
well sorted seds- all grains are mostly same size and shape
poorly sorted seds- different sizes
Angularity def
the shape of fragments( pieces of rock)
Non clastic
Classes of sed rocks are grouped bases on shape size and composition.
Classes of non clastic are…
Chemical precipitation- formed from minerals that were once in water ex limestone dolomite chert
chemical evaporation- water evapoartion is high and leabe evaporites- mineral left behind after evaporation ex gypsum, halite
organic- forms from remains of living things
Sedimentary rock features
Stratification- layering of the sed rock- happens when the conditions of the sed change over time
Bedding- is the (stratified) layers, which vary in thickness depending on the length of time during the sediment is deposited.
Massive beds- beds that have no structures forms for long period of time
Cross beds- slanting layers, form over river and sand dunes
Graded bedding- various sizes
Reverse grading- small grains are on the bottom, mudflows
ripple marks- caused by the action of wind or water
mud crack- muddy deposits dry and shrink
fossils- remains or traced of ancient plants
Weathering
rocks are broken down chemical and physically bu water air and organizms
Erosion
Earth materials are physically incorporated by moving water ice or wind
Deposition
Earth materials are carried by wind water or ice
Why are fossils only found in sed rocks
Dead plants and animals are buried by mire seds this results in the accumulation of minerals from water in bones which leads to fossils.
