Definition
A fjord is a sea inlet that has inundated a trough formed by
glacial erosion. Like the glaciers that formed the troughs,
fjords range in length from a few to hundreds of kilometers and are common in the modern and past glaciated portions of the Arctic, Antarctic, South America, northwest
Europe and Scandinavia, northern North America, and
New Zealand.
Origin and morphology
Although troughs erode rapidly under glacial conditions,
many fjords are erosionally complex, palimpsest features that formed over the course of multiple glacial episodes (Nesje and Whillans, 1994; Bennett and Glasser,
2009). Because glacial erosion is dependent on ice thickness, erosion rates are highest on the valley floors,
resulting in the common steep-sided U-shaped valley
forms. These cross-sectional profiles can be described
mathematically by empirical power-law functions or
second-order polynomials (Harbor and Wheeler, 1992;
Harbor, 1995; James, 1996; Amerson et al., 2008). However, profile asymmetry is common due to both the physical characteristics of the underlying bedrock and
subsequent erosional and depositional processes after
inundation (Augustinus, 1992; Nesje and Whillans,
1994; Augustinus, 1995). The longitudinal profile of
a fjord depicts the erosional and depositional characteristics of the formative glacier system with the deepest erosion and subsequent inundated water depths, coinciding
with the area of maximum ice discharge (Yingkui et al.,
2001). Reduced bedrock erosion and/or moraine deposition near the terminus of the past glacier extent results in
a shallow sill near the mouth of the fjord. The sills and
overdeepened troughs allow fjords to accumulate
a unique sedimentary archive of past marine and glacial
conditions (Benn and Evans, 2010). This same bathymetric juxtaposition also causes extreme currents and
inhibits exchange of bottom waters between the fjord
and adjacent sea (Farmer and Huppert, 1979; Farmer
and Freeland, 1983). The seasonal and annual mixing of
terrestrial and oceanic waters, coupled with various sea
ice and glacier inputs at high latitudes, yields complex
temperature, salinity, and density gradients both vertically
and between the head and the mouth of the fjord (Farmer
and Huppert, 1979; Farmer and Freeland, 1983).
Bibliography
Amerson, B., Montgomery, D. R., and Meyer, G., 2008. Relative
size of fluvial and glaciated valleys in central Idaho. Geomorphology, 93, 537–547.
Augustinus, P. C., 1992. The influence of rock mass strength on glacial valley cross-profile morphometry: a case study from the
Southern Alps, New Zealand. Earth Surface Processes and
Landforms, 17, 39–51.
Augustinus, P. C., 1995. Glacial valley cross-profile development:
the influence of in situ rock stress and rock mass strength, with
examples from the Southern Alps, New Zealand. Geomorphology, 14, 87–97.
Benn, D. I., and Evans, D. J., 2010. Glaciers and Glaciation.
Hodder Education.
Bennett, M., and Glasser, N., 2009. Glacial Geology: Ice Sheets and
Landforms, 2nd edn. Hoboken: Wiley.
Bronge, C., 1996. The excavation of the Storglasiären trough during
the Quaternary. Geografiska Annaler, 78, 163–169.
Farmer, D. M., and Freeland, H. J., 1983. The physical oceanography of fjords. Progress in Oceanography, 12, 147–219.
Farmer, D. M., and Huppert, H. E., 1979. The oceanography of
fjords. Nature, 280, 273–274.
Harbor, J. M., 1995. Development of glacial-valley cross sections
under conditions of spatially variable resistance to erosion. Geomorphology, 14, 99–107.
Harbor, J. M., and Wheeler, D. A., 1992. On the mathematical
description of glaciated valley cross sections. Earth Surface Processes and Landforms, 17, 477–485.
Holtedahl, H., 1967. Notes on the formation of fjords and fjord–
valleys. Geografiska Annaler, 49A, 188–203.
James, L. A., 1996. Polynomial and power functions for glacial
valley cross-section morphology. Earth Surface Processes and
Landforms, 21, 413–432.
Nesje, A., and Whillans, I. M., 1994. Erosion of Sognefjord,
Norway. Geomorphology, 9, 33–45.
Yingkui, L., Gengnian, L., and Zhijiu, C., 2001. Longitudinal variations in cross-section morphology along a glacial valley: a casestudy from the Tien Shan, China. Journal of Glaciology, 47,
243–250.
Cross-references
Coastal Bays
Firth
FLOCCULATION
Dorothy Joyce D. Marquez
Nannoworks Laboratory, National Institute of Geological
Sciences, University of the Philippines Diliman,
Quezon City, Philippines
Synonyms
Aggregation; Coagulation
Definition
Flocculation is a process of contact and adhesion whereby
dispersed particles are held together by weak physical
interactions.
Introduction
Flocculation has been widely used in water and wastewater treatment applications mainly for clarification and
reduction of suspended solids, respectively. Recently, it
has also been used as a cost-effective method for
harvesting microalgae for biomass for production of
food, feed, fuel, or chemicals (Vandamme et al., 2013).
Aside from these applications, in situ flocculation has
also been studied for years to understand sediment transport in different aquatic environments. In this regard,
Eisma (1986) defined flocculation as a natural process
FLOCCULATION
327
A fjord is a sea inlet that has inundated a trough formed by
glacial erosion. Like the glaciers that formed the troughs,
fjords range in length from a few to hundreds of kilometers and are common in the modern and past glaciated portions of the Arctic, Antarctic, South America, northwest
Europe and Scandinavia, northern North America, and
New Zealand.
Origin and morphology
Although troughs erode rapidly under glacial conditions,
many fjords are erosionally complex, palimpsest features that formed over the course of multiple glacial episodes (Nesje and Whillans, 1994; Bennett and Glasser,
2009). Because glacial erosion is dependent on ice thickness, erosion rates are highest on the valley floors,
resulting in the common steep-sided U-shaped valley
forms. These cross-sectional profiles can be described
mathematically by empirical power-law functions or
second-order polynomials (Harbor and Wheeler, 1992;
Harbor, 1995; James, 1996; Amerson et al., 2008). However, profile asymmetry is common due to both the physical characteristics of the underlying bedrock and
subsequent erosional and depositional processes after
inundation (Augustinus, 1992; Nesje and Whillans,
1994; Augustinus, 1995). The longitudinal profile of
a fjord depicts the erosional and depositional characteristics of the formative glacier system with the deepest erosion and subsequent inundated water depths, coinciding
with the area of maximum ice discharge (Yingkui et al.,
2001). Reduced bedrock erosion and/or moraine deposition near the terminus of the past glacier extent results in
a shallow sill near the mouth of the fjord. The sills and
overdeepened troughs allow fjords to accumulate
a unique sedimentary archive of past marine and glacial
conditions (Benn and Evans, 2010). This same bathymetric juxtaposition also causes extreme currents and
inhibits exchange of bottom waters between the fjord
and adjacent sea (Farmer and Huppert, 1979; Farmer
and Freeland, 1983). The seasonal and annual mixing of
terrestrial and oceanic waters, coupled with various sea
ice and glacier inputs at high latitudes, yields complex
temperature, salinity, and density gradients both vertically
and between the head and the mouth of the fjord (Farmer
and Huppert, 1979; Farmer and Freeland, 1983).
Bibliography
Amerson, B., Montgomery, D. R., and Meyer, G., 2008. Relative
size of fluvial and glaciated valleys in central Idaho. Geomorphology, 93, 537–547.
Augustinus, P. C., 1992. The influence of rock mass strength on glacial valley cross-profile morphometry: a case study from the
Southern Alps, New Zealand. Earth Surface Processes and
Landforms, 17, 39–51.
Augustinus, P. C., 1995. Glacial valley cross-profile development:
the influence of in situ rock stress and rock mass strength, with
examples from the Southern Alps, New Zealand. Geomorphology, 14, 87–97.
Benn, D. I., and Evans, D. J., 2010. Glaciers and Glaciation.
Hodder Education.
Bennett, M., and Glasser, N., 2009. Glacial Geology: Ice Sheets and
Landforms, 2nd edn. Hoboken: Wiley.
Bronge, C., 1996. The excavation of the Storglasiären trough during
the Quaternary. Geografiska Annaler, 78, 163–169.
Farmer, D. M., and Freeland, H. J., 1983. The physical oceanography of fjords. Progress in Oceanography, 12, 147–219.
Farmer, D. M., and Huppert, H. E., 1979. The oceanography of
fjords. Nature, 280, 273–274.
Harbor, J. M., 1995. Development of glacial-valley cross sections
under conditions of spatially variable resistance to erosion. Geomorphology, 14, 99–107.
Harbor, J. M., and Wheeler, D. A., 1992. On the mathematical
description of glaciated valley cross sections. Earth Surface Processes and Landforms, 17, 477–485.
Holtedahl, H., 1967. Notes on the formation of fjords and fjord–
valleys. Geografiska Annaler, 49A, 188–203.
James, L. A., 1996. Polynomial and power functions for glacial
valley cross-section morphology. Earth Surface Processes and
Landforms, 21, 413–432.
Nesje, A., and Whillans, I. M., 1994. Erosion of Sognefjord,
Norway. Geomorphology, 9, 33–45.
Yingkui, L., Gengnian, L., and Zhijiu, C., 2001. Longitudinal variations in cross-section morphology along a glacial valley: a casestudy from the Tien Shan, China. Journal of Glaciology, 47,
243–250.
Cross-references
Coastal Bays
Firth
FLOCCULATION
Dorothy Joyce D. Marquez
Nannoworks Laboratory, National Institute of Geological
Sciences, University of the Philippines Diliman,
Quezon City, Philippines
Synonyms
Aggregation; Coagulation
Definition
Flocculation is a process of contact and adhesion whereby
dispersed particles are held together by weak physical
interactions.
Introduction
Flocculation has been widely used in water and wastewater treatment applications mainly for clarification and
reduction of suspended solids, respectively. Recently, it
has also been used as a cost-effective method for
harvesting microalgae for biomass for production of
food, feed, fuel, or chemicals (Vandamme et al., 2013).
Aside from these applications, in situ flocculation has
also been studied for years to understand sediment transport in different aquatic environments. In this regard,
Eisma (1986) defined flocculation as a natural process
FLOCCULATION
327