11B – Slide 1
Topic 11B:
Deep-Sea Sediments
Online Lecture:
Deep-Sea Sediments
○ Kinds of Sediments
& Where They Are Found
○ Studying Sediments is Useful
○ Copepods & Sediments
Sediments & the Sea Floor
11B – Slide 2
Rocks
Shells
What are the 2 most common kinds of ocean sediments?
(In other words, what are ocean sediments made of?)
Lithogenous Sediments Come from the Land 11B – Slide 3
Most sink near shore:
very little reaches the deep ocean
Lithogenous sediments are carried away
from the land by winds and ocean currents.
"large" (and small) sediments
Continental
Shelf
Abyssal
Clay
Land
Ocean
Abyssal Clay
(only small sediments)
Biogenous “Oozes” sink as “Marine Snow”
Shells, mucous, fecal
matter, dead bodies,…
Marine
Snow
The longer
biogenous
sediments fall,
the more
they dissolve
11B – Slide 4
Shell
Shells dissolve
(“melt”) on the
way down
How does CO2 affect
the pH of ocean water?
calcium carbonate
dissolves in cold water,
so it “likes” warm water
Calcium carbonate
does not dissolve in
the warm water
at the surface
Calcareous Ooze
Winds and currents cannot carry much red clay into the
middle of the ocean (most red clay sinks closer to the coasts),
so there are a lot more sinking shells than red clay.
Silica dissolves
fast in the warm
water at the surface.
Silica dissolves slow
in the cold water
below the surface.
Calcium carbonate
begins to dissolve
in the colder water
below the surface.
If the ocean is too deep,
calcium carbonate completely
dissolves before reaching
the bottom.
11B – Slide 5
MOR
Mostly
calcium
carbonate
on the
bottom.
Warm
Cold
Red clay
does not
dissolve
on the way
to the
bottom
CCD
Mostly red clay
on the bottom
silica dissolves in
warm water, so it
“likes” cold water
Calcium carbonate
dissolves in
cold water.
If the ocean is too deep,
calcium carbonate
completely dissolves
before reaching
the bottom.
Mostly silica
on the bottom
Siliceous Ooze & Red Clay
11B – Slide 6
Winds and currents cannot carry much red clay into the
middle of the ocean (most red clay sinks closer to the coasts),
so there are a lot more sinking shells than red clay.
Silica dissolves
slow in
cold water.
Cool
Cold
CCD
If the ocean is
too deep, silica
dissolves
completely
before reaching
the bottom.
Red clay does not
dissolve on the
way to the bottom
Mostly red clay
on the bottom
Distribution of Deep-Ocean Sediments
11B – Slide 7
Abyssal Clay:
very deep water
Continental Material
Calcareous Ooze
Abyssal ("Red") Clay
Siliceous Ooze
Silica:
beneath cold water
Calcium Carbonate:
beneath warm water, not too deep
Why Do We Study Deep-Sea Sediments?
Sediment
“Core”
Sediment
“Core”
11B – Slide 8
Copepods & Sediments
11B – Slide 9
Fecal
Pellet
current
CCD
dense owing to shells,
sink quickly so they do
not dissolve as much