Transcript Seafloor Sediments

Warm-Up
Name three features on the ocean floor.
Continental shelf, slope, rise, submarine
canyon, abyssal plain, seamount, guyot
What is the difference between a guyot
and a seamount?
A guyot is a eroded seamount.
Which ocean has a smaller continental
shelf? Why?
The Pacific because the oceanic crust is
plunging below the continental crust
Seafloor Sediments &
Resources from the Seafloor
Chapter 14, Sections 3 & 4
Seafloor Sediments
 Most of the ocean floor is covered with sediment
 Some sediment is deposited by turbidity currents
 The rest of the sediment has slowly settled onto
the seafloor from above
 The sediment varies in thickness over the ocean
floor
 Ocean-floor sediments can be classified
according to their origin into three broad
categories: terrigenous sediments, biogenous
sediments, and hydrogenous sediments
Terrigenous Sediment
 Terrigenous Sediment – sediment that
originates on land
 Terrigenous sediments consist primarily of
mineral grains that were eroded from continental
shelf and continental rocks and transported to
the ocean
 Larger particles (gravel and sand) settle rapidly
near shore
 Finer particles (clay) may take years to settle on
the ocean floor and may be carried thousands of
kilometers by the ocean’s currents
 On continental shelves, the terrigenous
sediment is the thickest
Terrigenous Sediment
Biogenous Sediment
 Biogenous Sediment – sediment that is
biological in origin
 Biogenous sediments consist of shells and
skeletons of marine animals and algae
 Calcareous Ooze – produced from the calcium
carbonate shells of organisms
 Calcareous ooze has the consistency of thick
mud
 Siliceous Ooze – composed primarily of
diatoms—single-celled algae—and
radiolarians—single-celled animals that have
shells made out of silica
Biogenous Sediment
Hydrogenous Sediment
 Hydrogenous sediment consists of minerals that
crystallize directly from ocean water through
various chemical reactions
 These make up only a small portion of the
ocean’s sediments
 Manganese nodules are hard lumps of metals
which precipitate around grains of sand
 Calcium carbonates form by precipitation directly
from ocean water in warm climates
 Evaporites (salts) form where evaporation rates
are high and there is restricted open-ocean
circulation
Manganese Nodules
Distribution of Seafloor Sediments
Energy Resources
Oil and natural gas are the main energy
products currently being obtained from
the ocean floor
The ancient remains of microscopic
organisms are the source of today’s
deposits of oil and natural gas
The remains were buried and heated for
millions of years to be transformed into
oil and gas
Gas Hydrates
Gas Hydrates – compact chemical
structures of water and natural gas
Most oceanic gas hydrates are created
when bacteria break down organic matter
trapped in ocean-floor sediment
These bacteria produce methane gas
along with small amounts of ethane and
propane
Gas hydrates resemble chunks of ice, but
will ignite when lit by a flame
Gas Hydrates
Other Resources
Other major resources from the ocean floor
include sand and gravel, evaporative salts,
and manganese nodules
Sand and gravel from offshore are used for
landfill, to fill in recreational beaches, and to
make concrete; many high economic value
minerals can also be found in these deposits
(diamonds, gold, platinum, etc.)
Other Resources (continued)
Manganese Nodules – hard lumps of
manganese and other metals that
precipitate around a smaller object
The manganese nodules also contain
many minerals which have high economic
value (iron, copper, nickel, cobalt, etc.)
When seawater evaporates, the salts
increase in concentration until they no
longer remain dissolved and precipitate
out to form salt deposits
Salt Deposits
Assignment
Read Chapter 14, Section 3 (pg. 407-409)
Do Section 14.3 Assessment #1-6 (pg. 409)
Read Chapter 14, Section 4 (pg. 410-413)
Do Section 14.4 Assessment #1-8 (pg. 413)