Colluvium

Colluvium (also colluvial material or colluvial soil) is a general name for loose, unconsolidated sediments that have been deposited at the base of hillslopes by either rainwash, sheetwash, slow continuous downslope creep, or a variable combination of these processes. Colluvium is typically composed of a heterogeneous range of rock types and sediments ranging from silt to rock fragments of various sizes. This term is also used to specifically refer to sediment deposited at the base of a hillslope by unconcentrated surface runoff or sheet erosion.

Mass wasting in coastal Alaska (1969) (20385447860)
Mass wasting in coastal Alaska

Location

Colluviation refers to the buildup of colluvium at the base of a hillslope.[1][2] Colluvium is typically loosely consolidated angular material located at the base of a steep hill slope or cliff. Colluvium accumulates as gently sloping aprons or fans, either at the base of or within gullies and hollows within hillslopes. These accumulations of colluvium can be several meters in thickness and often contain buried soils (paleosols), crude bedding, and cut and fill sequences.

Talus cones
This talus accumulation is an example of colluvium

Importance

Thick accumulations of colluvium may preserve a rich record of long term paleoclimatic change based on the paleosols and the remains of plants and animals, invertebrate and vertebrates that they often contain.[2] These fossils indicate previous geologic and environmental settings. Thick accumulations of colluvium often contain well-preserved and sometimes deeply buried archaeological deposits as excavated at the Cherokee Sewer Site, Cherokee County, Iowa, and the Koster Site, Greene County, Illinois.[3][4] Colluvium can also be rocks that have been transported downward from glaciers and so can indicate past stages of cooler and/or wetter weather. Deposits of detrital colluvium can reveal the soil composition and signify processes of chemical weathering.

Compared to alluvium

The definitions of colluvium and alluvium are interdependent and reliant on one another. Distinctions between the two are important in order to properly define the geomorphic processes that have occurred in a specific geological setting. Alluvium is sand, clay, or other similar detrital material deposited by running water.[5] The distinction between colluvium and alluvium relates to the involvement of running water. Alluvium specifically refers to the geomorphic processes involved with flowing water and so alluvium is generally fine-grained clay and silt material that has the capacity to be entrained in water currents and eventually deposited. For these same reasons, alluvium is also generally well sorted material while colluvium is not.

See also

Koh Tao Island, Land erosion
The rate of the natural processes of erosion and colluvium accumulation are increased by human induced removal of native vegetation such as on Koh Tao Island in Thailand.

References

  1. ^ Jackson, JA, J Mehl, and K. Neuendorf (2005) Glossary of Geology American Geological Institute, Alexandria, Virginia. 800 pp. ISBN 0-922152-76-4
  2. ^ a b Goodie, AS (2003) Colluvium in A. S. Goodie, ed., pp. 173, Encyclopedia of Geomorphology Volume 1, A–I. Routledge, New York, New York. 1200 pp.
  3. ^ Anderson, D, and HA Semken (1980) The Cherokee Excavations: Holocene Ecology and Human Adaptations in Northwestern Iowa. Academic Press, New York.
  4. ^ Angel JR (1990) Koster site archaeology I: stratigraphy and landscape evolution. Research Series. vol. 8. Center for American Archeology, Kampsville, Illinois.
  5. ^ "colluvium | rock detritus and soil accumulated at the foot of a slope". www.merriam-webster.com. Retrieved 2015-12-13.

External links

Bearwallow Run

Bearwallow Run is a tributary of Shingle Mill Run in Sullivan County, Pennsylvania, in the United States. It is approximately 1.3 miles (2.1 km) long and flows through Davidson Township, Sullivan County, Pennsylvania. The watershed of the stream has an area of 1.02 square miles (2.6 km2). The stream is considered to be Class B Wild Trout Waters and wild trout reproduce naturally within it. The surficial geology in the area mainly consists of bedrock and Boulder Colluvium.

Bee Sellers Hollow

Bee Sellers Hollow is a tributary of Fishing Creek in Columbia County, Pennsylvania, in the United States. It is approximately 1.8 miles (2.9 km) long and flows through Stillwater. The watershed of Bee Sellers Hollow has an area of 1.58 square miles (4.1 km2). The stream is not considered to be impaired. The surficial geology in the area consists mainly of bedrock, along with alluvium, colluvium, Illinoian Till, and Illinoain Lag.

Big Run (West Branch Fishing Creek tributary)

Big Run is a tributary of West Branch Fishing Creek in Sullivan County, Pennsylvania, in the United States. It is approximately 1.0 mile (1.6 km) long and flows through Davidson Township. The watershed of the stream has an area of 0.51 square miles (1.3 km2). The stream is somewhat acidic, with a pH that ranged from 4.02 to 4.65 during a study on the watershed of Fishing Creek. Wisconsinan Till, Boulder Colluvium, and bedrock consisting of sandstone and shale all occur in the vicinity of the stream.

Channel (geography)

In physical geography, a channel is a type of landform consisting of the outline of a path of relatively shallow and narrow body of fluid, most commonly the confine of a river, river delta or strait. The word is cognate to canal, and sometimes takes this form, e.g. the Hood Canal.

Colluvium-filled bedrock hollow

Colluvium-filled bedrock hollows are the cause of many shallow earth landslides in steep mountainous terrain. They can form as a U or a V shaped trough as local bedrock variations reveal areas in the bedrock which are more prone to weathering than other locations on the slope. As the weathered bedrock turns to soil, there is a greater elevation difference between the soil level and the hard bedrock. With the introduction of water and the thick soil, there is less cohesion and the soil flows out in a landslide. With every landslide more bedrock is scoured out and the hollow becomes deeper. After time, colluvium fills the hollow, and the sequence starts again.

Flatiron (geomorphology)

Traditionally in geomorphology, a flatiron is a steeply sloping triangular landform created by the differential erosion of a steeply dipping, erosion-resistant layer of rock overlying softer strata. Flatirons have wide bases that form the base of a steep, triangular facet that narrows upward into a point at its summit. The dissection of a hogback by regularly spaced streams often resulted in the formation of a series of flatirons along the strike of the rock layer that formed the hogback. As noted in some, but not all definitions, a number of flatirons are perched upon the slope of a larger mountain with the rock layer forming the flatiron inclined in the same direction as, but often at a steeper angle than the associated mountain slope. The name flatiron refers their resemblance to an upended, household flatiron.The Flatirons near Boulder, Colorado, is both an example of these landforms and the source of their name. Other well-developed flatirons are found in the eastern Uinta Mountains in northwestern Colorado, the Waterpocket Fold in Capitol Reef National Park, the Superstition Mountains near Phoenix, Arizona and on the flanks of the Marathon Uplift in west Texas.The term "flatiron" is also used for very small-scale landforms that are known as pediment flatirons and talus flatirons. These landforms are small knolls with a triangular to trapezoidal-shaped sloping surface with the long side of this surface as their base and a point at their top. Both pediment flatirons and talus flatirons are associated with the scarps of a cuesta, mesa, or butte and with their tips directed towards the scarp. Both types of these flatirons are typically separated from the scarp by well-defined ravines and gullies. These flatirons consist of either talus, in the case of the talus flatirons, or pedisediment and colluvium that cover pediments, in the case of pediment flatirons. Their surfaces are protected by a thin layer of caprock. The caprock commonly consists of caliche, which is about 2 meters (6.6 ft) thick and rarely as much as 5 meters (16 ft) thick, that has developed in either talus, pedisediment, or colluvium. Talus flatirons lie within the scarp slope – and pediment flatirons occur within the transition zone between scarp and foreland. Pediment flatirons can merge downward into a fluvial terrace. Both talus and pediment flatirons are the relict remnants of formerly active slope systems that were once part of the scarp's history.

Head (geology)

Head describes deposits consisting of fragmented material which, following weathering, have moved downslope through a process of solifluction. The term has been used by British geologists since the middle of the 19th century to describe such material in a range of different settings from flat hilltops to the bottoms of valleys. Areas identified as head include deposits of aeolian origin such as blown sand and loess, slope deposits such as gelifluctates and solifluctates, and recently eroded soil material, called colluvium. With geologists becoming more interested in studying the near-surface environment and its related processes, the term head is becoming obsolete.

A related term is 'combe (or coombe) rock', descriptive of a body of chalk and flint fragments contained within a mass of chalky earth typically found on the chalk downlands of south-east England and resulting from freeze-thaw processes. Where the mass is also soliflucted, it is considered a variety of head.Though its earliest use is attributed to De la Beche in 1839 he mentions that in 1837 Mr.Trevelyn of Guernsey observed “ a bed of disintegrated granite, about three feet thick, mixed with angular fragments, thus reminding us of the head of angular fragments so commonly seen in Cornwall and Devon.“

Jory (soil)

The Jory series consists of very deep, well-drained soils that formed in colluvium derived from basic igneous rock. These soils are in the foothills surrounding the Willamette Valley of the United States. They have been mapped on more than 300,000 acres (1,200 km2) in western Oregon. They are named after Jory Hill, Marion County, Oregon, which itself is named for the Jory family, who settled in the area in 1852, after traveling along the Oregon Trail.

Surface layer: organic material

Subsurface layer: dark reddish brown silty clay loam

Subsoil - upper: dark reddish brown clay

Subsoil - lower: red clayJory soils generally support forest vegetation, dominantly Douglas fir and Oregon white oak. They are very productive forest soils. Many areas have been cleared and are used for agricultural crops. The Jory soils and the climate of the Willamette Valley provide an ideal setting for the production of many crops, including Christmas trees, various berries, filberts (hazelnuts), sweet corn, wheat, and many varieties of grass seed. The soils are suitable for the grapes used in the expanding Oregon wine industry.

Growing urbanization of the Willamette Valley is resulting in a great deal of pressure for development in areas of the Jory soils.

Karnes Hollow

Karnes Hollow is a tributary of Fishing Creek in Columbia County, Pennsylvania, in the United States. It is approximately 1.1 miles (1.8 km) long and flows through Fishing Creek Township and Benton Township. The watershed of the stream has an area of 0.90 square miles (2.3 km2). The stream is named after a valley whose etymology is unknown. The surficial geology in its vicinity consists of colluvium, alluvium, Illinoian Till, Illinoian Lag, and bedrock consisting of sandstone and shale.

Lake Run

Lake Run is a tributary of Roaring Brook in Lackawanna County, Pennsylvania, in the United States. It is approximately 1.6 miles (2.6 km) long and flows through Covington Township. The watershed of the stream has an area of 3.44 square miles (8.9 km2). It has one named tributary, which is known as Emerson Run. Lake Run is considered to be Class A Wild Trout Waters. The surficial geology in its vicinity consists of Wisconsinan Ice-Contact Stratified Drift, Wisconsinan Till, Boulder Colluvium, alluvium, bedrock, sand and gravel pits, fill, wetlands, peat bogs, and a lake.

Laurel Run (West Branch Fishing Creek tributary)

Laurel Run is a tributary of West Branch Fishing Creek in Sullivan County, Pennsylvania, in the United States. It is approximately 1.2 miles (1.9 km) long and flows through Davidson Township. The stream is in the United States Geological Survey quadrangle of Elk Grove. Wisconsinan Flow-Till, Boulder Colluvium, Wisconsinan Till Moraine, alluvium, and alluvial fan occur in the vicinity of the stream, as does bedrock consisting of sandstone and shale. The southern terminus of the late Wisconsinan glaciation is also in the area. A wood plank bridge on stone masonry abutment walls crosses the stream.

North Branch Bowman Creek

North Branch Bowman Creek is a tributary of Bowman Creek in Luzerne County, Pennsylvania, in the United States. It is approximately 3.2 miles (5.1 km) long and flows through Fairmount Township and Ross Township. The watershed of the creek has an area of 2.63 square miles (6.8 km2). The creek is not designated as an impaired waterbody. The surficial geology in its vicinity includes Wisconsinan Till, alluvial fan, Boulder Colluvium, alluvium, bedrock, and a peat bog. The creek is mostly in Pennsylvania State Game Lands and Ricketts Glen State Park.

The drainage basin of North Branch Bowman Creek is designated as a High-Quality Coldwater Fishery and a Migratory Fishery. The creek has been stocked with fish in the past, but also has wild trout. There is a hiking trail that is located in its vicinity. An 11-acre (4.5 ha) natural lake is situated on the creek.

Panguipulli Formation

Panguipulli Formation (Spanish: Formación Panguipulli) is a sedimentary formation of Triassic age located in Los Ríos Region and southernmost Araucanía Region in south–central Chile. The formation is variously covered by Quaternary lavas in the east and Quaternary moraines, Holocene alluvium and colluvium in the west. The formation and make up possibly the remnants of an ancient lake and river system. The formation is named after the town of Panguipulli on the western edge of Panguipulli Lake. The formation has evidence of low grade metamorphism and is locally intruded by plutons of the North Patagonian Batholith that are of Jurassic, Cretaceous and Miocene age.

Plank Bridge Creek

Plank Bridge Creek is a tributary of Spring Brook in Lackawanna County, Pennsylvania, in the United States. It is approximately 2.4 miles (3.9 km) long and flows through Spring Brook Township. The watershed of the creek has an area of 1.26 square miles (3.3 km2). It is inhabited by wild trout throughout its length. The surficial geology in its vicinity mainly consists of Wisconsinan Till, bedrock, Boulder Colluvium, alluvium, and wetlands.

Rocky Run (Susquehanna River tributary)

Rocky Run (also known as Rocky Run Creek) is a tributary of the Susquehanna River in Luzerne County, Pennsylvania, in the United States. It is approximately 2.3 miles (3.7 km) long and flows through Salem Township. The watershed of the stream has an area of 1.83 square miles (4.7 km2). In the early 1900s, the stream had a high level of water quality and was proposed for use as a water supply. The construction of a dam on it was proposed, but no formal plans were ever made. There are coal mines in the watershed, but they have been abandoned since the late 1800s. Wisconsinan Till, Wisconsinan Ice-Contact Stratified Drift, Boulder Colluvium, Wisconsinan Bouldery Till, coal dumps, and bedrock consisting of sandstone and shale all occur in the watershed. The drainage basin is designated as a Coldwater Fishery.

Shingle Mill Run

Shingle Mill Run is a tributary of West Branch Fishing Creek in Sullivan County, Pennsylvania, in the United States. It is approximately 2.4 miles (3.9 km) long and flows through Davidson Township. The watershed of the stream has an area of 2.60 square miles (6.7 km2). The stream has one named tributary, Bearwallow Run. Shingle Mill Run is designated as an Exceptional Value stream and has a population of native trout. The stream has high water quality and is slightly acidic. Boulder Colluvium and bedrock consisting of sandstone and shale can be found near the stream.

South Branch Bowman Creek

South Branch Bowman Creek (also known as Cherry Run) is a tributary of Bowman Creek in Luzerne County, Pennsylvania, in the United States. It is approximately 3.0 miles (4.8 km) long and flows through Fairmount Township and Ross Township. The watershed of the creek has an area of 3.92 square miles (10.2 km2). The surficial geology in its vicinity consists of alluvial fan, alluvium, Wisconsinan Ice-Contact Sratified Drift, fill, lakes, Boulder Colluvium, Wisconsinan Till, Wisconsinan Bouldery Till, wetlands, and bedrock. Most of the creek is in Ricketts Glen State Park. It has one named tributary, which is known as Cherry Run. The creek's watershed is designated as a High-Quality Coldwater Fishery and a Migratory Fishery.

Spencer Run

Spencer Run (also known as Spencer's Run) is a tributary of West Creek in Columbia County, Pennsylvania, in the United States. It is approximately 2.1 miles (3.4 km) long and flows through Jackson Township and Benton Township. The watershed of the stream has an area of 2.07 square miles (5.4 km2). Wild trout naturally reproduce in the stream. The surficial geology in the area mainly features Illinoian Till, Illinoian Leg, alluvium, colluvium, and bedrock.

York Hollow

York Hollow (also known as Yorks Hollow or York's Hollow) is a tributary of West Creek in Columbia County, Pennsylvania, in the United States. It is approximately 2.5 miles (4.0 km) long and flows through Jackson Township and Sugarloaf Township. The watershed of the stream has an area of 1.47 square miles (3.8 km2). Wild trout naturally reproduce in the stream. The surficial geology in the area mainly consists of Illinoian Till, Illinoian Lag, alluvium, colluvium, and bedrock.

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