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8/2/2019 Abyssal Plains - Handout
http://slidepdf.com/reader/full/abyssal-plains-handout 1/2
Abyssal plains - vast, flat, sediment-covered areas of
the deep ocean floor
- flat seafloor area at an abyssal depth (3,000 to
6,000 m [10,000 to 20,000 feet]), generally adjacent to a
continent, submarine surfaces vary in depth only from 10
to 100 cm per kilometre of horizontal distance.
Irregular in outline but generally elongate along
continental margins
-the lack of features is due to a thick blanket of
sediment that covers most of the surface
-Seismic profiles (cross sections) of abyssal
plains reveal accumulations of sediment averaging one
kilometre in thickness, deposited on undulating
topography
-common in the Atlantic, less common in the
Indian Ocean, and even rarer in the Pacific
Location - near the Pelagic zone – open ocean (water is
not at bottom or near the shore), specifically, located in
the Abyssopelagic layer (4,000 – 6,000 m)
-covered with pelagic mud (mud which is not yet
thoroughly known, but contains complex minerals) with
fine sand layers from nearby turbidites (type
of sedimentary rock composed of layered particles that
grade upward from coarser to finer sizes and are thought
to have originated from ancient turbidity currents in the
oceans, integral components of sedimentary deep-sea
fans adjacent to the base of continental slopes, and they
are also found below the major river deltas of the world
where they build features called abyssal cones)
Formation – turbidity current (sediments)
- underwater density current
of abrasive
sediments, thought to be caused by the slumping of
sediment that has piled up at the top of the continental
slope
-decompression melting (plain itself)
-similar to spreading centers (diverging
plates cause parts of upper mantle to move upward and
solidify by conduction or convection)
-seafloor spreading – new oceanic crust
is formed and gradually moves away
-forms in the Abyssopelagic zone (more common
in the Atlantic)
SEDIMENTARY ROCKS PRESENT
1. Marlstone – freshwater limestone, lime-rich
mudstone
http://www.citizendia.org/Marl
2. Calcilutite – limestone mud
http://search.datapages.com/data/doi/10.1306/74D7
15C3-2B21-11D7-8648000102C1865D
3. Micrite – fine-grained limestone
http://www.fp.sfasu.edu/geology/geologytutorial/Roc
ks/sld032.htm
4. Chert – a form of microcrystalline quartz
http://geology.com/rocks/chert.shtml
5. Turbidite - v
ertical sequence of sediments
deposited by a turbidity current
http://petrogroupcompany.com/infoCurso.php?
idCurso=27
8/2/2019 Abyssal Plains - Handout
http://slidepdf.com/reader/full/abyssal-plains-handout 2/2
ANIMALS POSSIBLY PRESENT
1. Rattail fish/Grenadier fish
http://www.allthesea.com/Deep-Sea-Fish-Rattail-
Fish.html
2. Black lizardfish/deep-water greeneye
3. Feeler fish
4.
Abyssobrotula galatheae – a species of cusk
eel
5. Abyssal spiderfish
-look at http://www.cedamar.dzmb.net/Species-
List for a complete list of abyssal plain animals
(too many, more than 200)
ABYSSAL PLAINS
http://m.eb.com/assembly/86712
http://elearning.stkc.go.th/lms/html/earth_science/LO
canada6/604/9_en.htm
http://science.howstuffworks.com/environmental/gre
en-science/bury-co2-in-ocean2.htm
Sources
http://www.britannica.com/facts/5/6190
96/abyssal-plain-as-discussed-in-
sedimentary-rock
http://www.universetoday.com/74357/a
byssal-plain/
http://www.britannica.com/EBchecked/t
opic/2483/abyssal-plain