H4 Flashcards
what is sediment
- minerals (pieces of stone)
- fossils (imprints of shells or dead organic material)
- or a mix of minerals and fossils
types of sediments based on origin (5)
- terrigenous
- biogenic
- hydrogenous
- volcanogenic
- cosmogenous
examples of terrigenous sediment
sand and clay
examples of biogenous sediment
chalk and silicious mud (kiezelhoudend modder)
types of sediments based on grain size (4)
- gravel (grind/kiezel)
- sand
- silt (slik)
- clay (klei)
pebble grain size
4-64 mm
granules grain size
2-4 mm
coarse sand grain size
0.5-2 mm
medium sand grain size
0.25-0.5 mm
fine sand grain size
0.06-0.25 mm
silt grain size
0.004-0.06 mm
clay grain size
less than 0.004 mm
which two factors influence sedimentation?
- grain size
2. turbulence/ energy in the system/environment
what happens in an environment with a lot of energy?
the water is turbulent and the smallest sediment grains are returned to the water column. grain size is relatively large
where do the smallest grains often land?
in a calmer environment, which is often deeper
where do clay-sized particles often land
furthest from shore in calm waters
what happens in an environment with low energy?
grain size is relatively small
erosion
the process disintegration of sediment by chemical or mechanical processes
deposition
the process of placing, or deposition of sediment
Hjulstrom’s diagram
A diagram showing the relationship in a channel between particle size and the mean fluid velocity required for entrainment. It shows that an entrained particle can be transported in suspension at a lower velocity than that required to lift the particle initially. When the stream velocity slows to a critical speed, the particle is deposited. Note that higher velocities are needed for the entrainment of clay-sized particles because of the electrostatic forces which bind them together.
