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SCI 245 Sedimentary Rocks WK 5




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Sedimentary Rocks 1
Sedimentary Rocks
Axia College
Plate tectonics affect where sediment falls to the way that rocks are formed

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Sedimentary Rocks 2
from the sediment. There are three different types of sediment rocks that are created in
similar manner but actual make up each sediment rock is very difficult. There is clastic
sediment that will form clastic sedimentary rock, chemical sediment that will form
chemical rock, and then there is Biogenic sediment that will eventually form Biogenic
sedimentary rock. This happens in many different ways and plate tectonics help this
process all along the way. “Divergent margins create rift valleys and passive continental
margins. Colliding tectonics plates create structural basins and valleys associated with
mountain ranges as a result of the folding and faulting of rock. Subducting plates form
deep oceanic trenches along with volcanic arcs that may have back-arc basins. All of
these locations are effective traps for sediment.” (From Sediment to Sedimentary Rock,
2008). Convergent plate boundaries can usually be found on the edges of high mountain
ranges due to plate collisions. When pieces of the mountain breaks off it falls to low-
lying areas as gravel and sand. Convergent plate boundaries lie in very low-lying
trenches caused by the subduction of plates. The sediment will pile up quickly because
these areas are so steep. Once sediment has settled it will then begin the process in
becoming a rock.
Sediment goes through a process called “lithification” that enables the sediment to
form rock. The sediment is transformed into rock by various procedures. Most of the

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Sedimentary Rocks 3
time, rock is first compacted. Once the layer of sediment is completely covered, it is
then pressure is applied by other sediment on that is above it or from tectonic processes
that also apply pressure to it. Then there becomes much less pore space and the
sediment becomes compacted. Another way lithification can happen is by cementation.
If any are becomes very dry and hot the land will loose a lot of water by precipitation.
When the water evaporates, the chemicals will precipitate and cement the sediment
together. Another common way of lithification can happen is by re-crystallization which
is where old mineral grains, that were separate, will form new crystalline mineral grains.
All of these ways will include the lithification process than will form sedimentary rocks.
The appearance of sedimentary rock can also vary depending on environmental
differences in the area that the rock is located. Differences can range from grain size,
grain shape, stratification, color, chemical composition, depositional structure, or
fossils. These rocks are also formed in many different ways based on the make up of the
sediment that form them.
The most abundant sedimentary rock is formed by clastic sediment which collects
in low lying areas. Clastic sediment is formed from small, individual minerals and rock
that are formed by weathering of the small debris and combined with broken remains of
organisms. These small minerals and rock could be smaller than a grain of flour or as

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