Transcript A Sediment*s Story

Sediment Notes
What can sediments tell us
about our beach?
Color
Color can help you identify what
mineral the sediment is made of. This
can help you determine its source.
Waianapanapa State Park - Maui, Hawaii
Ponte Vedra Beach, Florida
(tiny red coral organisms)
Puu Mahana - Big Island of Hawaii
(Olivine-rich rocks)
Puu Mahana
Island of Hawaii
Caladesi
Beach- –Big
Clearwater,
Florida
(Quartz-rich rocks)
Pfeiffer Beach, Big Sur, California
(garnet-rich rocks)
Rockaway Beach, Pacifica, California
(bluish-gray limestone mixing with volcanic greenstone)
Santorini, Greece
(Iron-rich rocks from red lava cliffs)
Shape
Rivers smooth out the surface of a
sediment grain as it travels to the ocean. In
general, the rounder the sediment is, the
farther it has traveled from its source.
• The hardness of the mineral can also
affect the roundness of a particle.
Is the source close or far?
Quartz grains,
which are very
hard, are pretty
rounded, which
means it probably
traveled a long
way.
Is the source close or far?
These grains are
very angular, so
they have only
traveled a very
short distance
from the source.
Is the source close or far?
Notice some
grains are not
very rounded…
While some
grains are very
rounded.
The minerals are
different & get
weathered at
different rates.
Size
Small sediments =low energy beach
(small to no waves)
Large sediments =high energy beach
(big, strong waves)
Aleutian Islands
Biggest
Smallest
Boulders
Cobbles
Pebbles
Sand
Silt
Clay
High wave energy
Low wave energy
4 TYPES OF SEDIMENTS
•
Terrigenous - from continents
•
Biogenous – plant or animal origin
•
Hydrogenous - precipitated from water
•
Cosmogenous - from outer space
TERRIGENOUS SEDIMENTS
• Most common type of sediment
• Composed of weathered rock material
from land
*Most common composition:
QUARTZ
CLAY MINERALS
TERRIGENOUS SED. CONT.
*On continental margins:
- Carried to the ocean by rivers
- Coarse sediment is nearest to the shore
- Finer sediment is found offshore
*In ocean basins:
- Carried by turbidity currents & found
near continents
- Very fine sediment could be blown far
from land by wind.
BIOGENOUS SEDIMENTS
*From benthic organisms:
-coral reef debris &
shell fragments
Click me to see me make sand!
*From zooplankton
- Calcium carbonate composition:
Foraminifera & Coccolithophores
- Silicate composition:
Radiolaria & Diatoms
HYDROGENOUS SEDIMENTS
*Manganese nodules (deep ocean basin)
from:
- hydrothermal vent water
*Evaporites:
Restricted circulation + high evaporation=
precipitation of salts
COSMOGENOUS SEDIMENTS
• Always <1% of a sediment
• Rain down uniformly from space,
but most abundant in deep ocean
sediments because not "diluted"
by other kinds of sediments
*Meteorite fragments & dust
*Rare earth elements