14.3 Seafloor Sediments: Types of Seafloor Sediments

Explanation of Topic
(Definition, Key Points, Details)

Seafloor sediments are sediments that compose the seafloor. They are tiny mineral grains or sometimes larger particles that cover the ocean floor. These sediments can be classified into 3 main categories based on origin.

1. The first type of seafloor sediment is Terrigenous sediment. Terrigenous sediment originates on land. It consists primarily of mineral grains that have eroded from continental rocks & have been transported to the ocean. Larger particles such as gravel & sand usually settle rapidly near shore. The finer particles like clay can take years to settle & can travel thousands of kilometers.

2. The second type of seafloor sediment is Biogenous sediment. Biogenous sediment is biological in origin. It consists of shells & the skeletons of marine animals & algaes. It is mostly produced by microscopic organisms living in surface waters, which then die, then the shells sink to the ocean floor. There are several common biological sediments.

A. The first & most common biogenous sediment is Calcareous ooze. Calcareous ooze is produced from calcium carbonate shells of organisms. These shells sink into deeper parts of the ocean & then dissolve & form the consistency of thick mud.

B. The second biogenous sediment is Siliceous ooze. Siliceous ooze is composed primarily of diatoms (diatoms- single celled algaes) shells & radiolarians (single celled animals that have shells made of silica).

3. The third type of of seafloor sediment is Hydrogenous sediment. Hydrogenous sediment consists of minerals that have crystalized directly from ocean water through various chemical reactions. There are several examples of terrigenous sediments.

A. The first example of a terrigenous sediment is Manganese nodules. Manganese nodules are round, hard lumps of manganese, iron, & other metals that precipitates around objects like sand grains. Manganese nodules are usually scattered about the seafloor & can be up to 20 centimeters large in diameter.

B. The second example of terrigenous sediments are Calcium Carbonates. Calcium carbonate precipitates directly from the ocean in warm climates. If buried & hardened a limestone-type forms.

Visual Examples
(Pictures, Graphics, Animations)

Picture of Terrigenous Sediment--------------------------------Picture of Biogenous Sediment------------------------------------(Diatom below) Another Biogenous Sediment Pic
external image thenat75.jpg external image radsediments.gif external image sed2.jpg
Note the sand, rocks, gravel, & large particles.------------Note the coral.-----------------------------------------------------------Note the diatoms.

Picture of Hydrogenous Sediment
external image thumbnail.aspx?q=320287879578&id=f99c6d791e0515fa0aecf197d3c8b1cd&url=http%3a%2f%2ffiles.myopera.com%2fnielsol%2fblog%2fmanganese_nodule.jpg
This is a manganese nodule; a type
of hydrogenous sediment.

Links to more information:

Interesting Facts or Discoveries:
Oceanographers study seafloor sediment by taking long cylindrical cores that measure between 60-98 feet.
Terrigenous sediment is well-preserved on the seafloor.
Biogenous sediment is poorly preserved on the floor of the ocean.

Works Cited:
Chapter 14.3 Seafloor Sediments: Types of Seafloor Sediment in our science text book
Picture 1.- http://www.chucksaddiction.com/thenat75.jpg
Picture 2.- http://oceanz.tamu.edu/~wormuth/marinesediments/radsediments.gif
Picture 3.- http://www.jochemnet.de/fiu/sed2.jpg
Picture 4.- http://files.myopera.com/nielsol/blog/manganese_nodule.jpg
Interesting Facts/ Discoveries- http://www.encyclopedia.com/doc/1G2-3409400234.html