Editing Geomorphology (section)

== Processes ==
[[File:Nanga_Parbat_Indus_Gorge.jpg|thumb|[[Gorge]] cut by the [[Indus River]] into bedrock, [[Nanga Parbat]] region, Pakistan. This is the deepest river canyon in the world. Nanga Parbat itself, the world's 9th highest mountain, is seen in the background.]]
Geomorphically relevant processes generally fall into
(1) the production of [[regolith]] by [[weathering]] and [[erosion]],
(2) the [[sediment transport|transport]] of that material, and
(3) its eventual [[deposition (geology)|deposition]]. Primary surface processes responsible for most topographic features include [[wind]], [[wave]]s, [[weathering|chemical dissolution]], [[mass wasting]], [[groundwater]] movement, [[surface water]] flow, [[glacier|glacial action]], [[tectonism]], and [[volcanism]]. Other more exotic geomorphic processes might include [[periglacial]] (freeze-thaw) processes, salt-mediated action, changes to the seabed caused by marine currents, seepage of fluids through the seafloor or extraterrestrial impact.

=== Aeolian processes ===
[[File:MoabAlcove.JPG|thumb|Wind-eroded alcove near [[Moab, Utah]]]]
[[Aeolian processes]] pertain to the activity of the [[wind]]s and more specifically, to the winds' ability to shape the surface of the [[Earth]]. Winds may erode, transport, and deposit materials, and are effective agents in regions with sparse [[vegetation]] and a large supply of fine, unconsolidated [[sediment]]s. Although water and mass flow tend to mobilize more material than wind in most environments, aeolian processes are important in arid environments such as [[desert]]s.<ref>{{cite book|last=Leeder |first=M. |date=1999 |title=Sedimentology and Sedimentary Basins, From Turbulence to Tectonics |publisher=[[Wiley-Blackwell|Blackwell Science]] |page=592 |isbn=0-632-04976-6}}</ref>

=== Biological processes ===
[[File:Beaver dam in Tierra del Fuego.jpg|thumb|[[Beaver eradication in Tierra del Fuego|Beaver dams]], as this one in [[Tierra del Fuego]], constitute a specific form of zoogeomorphology, a type of biogeomorphology.]]
The interaction of living organisms with landforms, or [[Biogeomorphology|biogeomorphologic processes]], can be of many different forms, and is probably of profound importance for the terrestrial geomorphic system as a whole. Biology can influence very many geomorphic processes, ranging from [[biogeochemical]] processes controlling [[chemical weathering]], to the influence of mechanical processes like [[burrowing]] and [[tree throw]] on soil development, to even controlling global erosion rates through modulation of climate through carbon dioxide balance. Terrestrial landscapes in which the role of biology in mediating surface processes can be definitively excluded are extremely rare, but may hold important information for understanding the geomorphology of other planets, such as [[Geography of Mars|Mars]].<ref>{{cite journal |last1=Dietrich |first1=William E. |last2=Perron |first2=J. Taylor |title=The search for a topographic signature of life |journal=[[Nature (journal)|Nature]] |date=26 January 2006 |volume=439 |issue=7075 |pages=411–418 |doi=10.1038/nature04452 |pmid=16437104 |bibcode=2006Natur.439..411D |s2cid=4417041}}</ref>

=== Fluvial processes ===
[[File:Eroding Mesas Forming Seif and Barchan Dunes in Hellespontus region.jpg|thumb|[[Seif dune|Seif]] and [[barchan]] dunes in the [[Noachis quadrangle|Hellespontus]] region on the surface of [[Mars]]. Dunes are mobile landforms formed by the transport of large volumes of sand by wind.]]
{{Main|Fluvial}}
{{See also|Hack's law|Sediment transport}}
Rivers and streams are not only conduits of water, but also of [[sediment]]. The water, as it flows over the channel bed, is able to mobilize sediment and transport it downstream, either as [[bed load]], [[suspended load]] or [[dissolved load]]. The rate of sediment transport depends on the availability of sediment itself and on the river's [[discharge (hydrology)|discharge]].<ref>{{cite book|last=Knighton |first=D. |date=1998 |title=Fluvial Forms & Processes |publisher=[[Hodder Arnold]] |page=383 |isbn=0-340-66313-8}}</ref> Rivers are also capable of eroding into rock and forming new sediment, both from their own beds and also by coupling to the surrounding hillslopes. In this way, rivers are thought of as setting the base level for large-scale landscape evolution in nonglacial environments.<ref>{{cite journal |last=Strahler |first=A. N. |title=Equilibrium theory of erosional slopes approached by frequency distribution analysis; Part II |journal=[[American Journal of Science]] |date=1 November 1950 |volume=248 |issue=11 |pages=800–814 |doi=10.2475/ajs.248.11.800 |bibcode=1950AmJS..248..800S|doi-access=free }}</ref><ref>{{cite journal |last=Burbank |first=D. W. |title=Rates of erosion and their implications for exhumation |journal=[[Mineralogical Magazine]] |date=February 2002 |volume=66 |issue=1 |pages=25–52 |doi=10.1180/0026461026610014 |url=http://projects.crustal.ucsb.edu/tectgeomorphfigs/Min_Mag_exhumation_ms.pdf |bibcode=2002MinM...66...25B |citeseerx=10.1.1.518.6023 |s2cid=14114154 |access-date=2012-09-29 |archive-url=https://web.archive.org/web/20130315035544/http://projects.crustal.ucsb.edu/tectgeomorphfigs/Min_Mag_exhumation_ms.pdf |archive-date=2013-03-15 |url-status=dead}}</ref> Rivers are key links in the connectivity of different landscape elements.

As rivers flow across the landscape, they generally increase in size, merging with other rivers. The network of rivers thus formed is a [[drainage system (geomorphology)|drainage system]]. These systems take on four general patterns: dendritic, radial, rectangular, and trellis. Dendritic happens to be the most common, occurring when the underlying stratum is stable (without faulting). Drainage systems have four primary components: [[drainage basin]], alluvial valley, delta plain, and receiving basin. Some geomorphic examples of fluvial landforms are [[alluvial fan]]s, [[oxbow lake]]s, and [[fluvial terrace]]s.

=== Glacial processes ===
[[File:Glacial landscape LMB.png|thumb|right|Features of a glacial landscape]]
[[Glacier]]s, while geographically restricted, are effective agents of landscape change. The gradual movement of [[ice]] down a valley causes [[Abrasion (geology)|abrasion]] and [[Plucking (glaciation)|plucking]] of the underlying [[rock (geology)|rock]]. Abrasion produces fine sediment, termed [[glacial flour]]. The debris transported by the glacier, when the glacier recedes, is termed a [[moraine]]. Glacial erosion is responsible for U-shaped valleys, as opposed to the V-shaped valleys of fluvial origin.<ref>{{Cite book|last1=Bennett |first1=M.R. |last2=Glasser |first2=N.F. |date=1996 |title=Glacial Geology: Ice Sheets and Landforms |publisher=[[John Wiley & Sons]] Ltd |page=364 |isbn=0-471-96345-3}}</ref>

The way glacial processes interact with other landscape elements, particularly hillslope and fluvial processes, is an important aspect of [[Plio-Pleistocene]] landscape evolution and its sedimentary record in many high mountain environments. Environments that have been relatively recently glaciated but are no longer may still show elevated landscape change rates compared to those that have never been glaciated. Nonglacial geomorphic processes which nevertheless have been conditioned by past glaciation are termed [[paraglacial]] processes. This concept contrasts with [[periglacial]] processes, which are directly driven by formation or melting of ice or frost.<ref>{{cite journal |last1=Church |first1=Michael |last2=Ryder |first2=June M. |s2cid=56240248 |title=Paraglacial Sedimentation: A Consideration of Fluvial Processes Conditioned by Glaciation |journal=[[Geological Society of America Bulletin]] |date=October 1972 |volume=83 |issue=10 |pages=3059–3072 |doi=10.1130/0016-7606(1972)83[3059:PSACOF]2.0.CO;2 |bibcode = 1972GSAB...83.3059C}}</ref>

=== Hillslope processes ===
[[File:TalusConesIsfjorden.jpg|thumb|[[Talus cone]]s on the north shore of [[Isfjorden (Svalbard)|Isfjorden]], [[Svalbard]], Norway. Talus cones are accumulations of coarse hillslope debris at the foot of the slopes producing the material.]]
[[Image:Ferguson-slide.jpg|thumb|The [[Ferguson landslide|Ferguson Slide]] is an active [[landslide]] in the [[Merced River|Merced River canyon]] on [[California State Highway 140]], a primary access road to [[Yosemite National Park]].]]
[[Soil]], [[regolith]], and [[rock (geology)|rock]] move downslope under the force of [[gravity]] via [[Downhill creep|creep]], [[Landslide|slides]], flows, topples, and falls. Such [[mass wasting]] occurs on both terrestrial and submarine slopes, and has been observed on [[Earth]], [[Mars]], [[Venus]], [[Titan (moon)|Titan]] and [[Iapetus (moon)|Iapetus]].

Ongoing hillslope processes can change the topology of the hillslope surface, which in turn can change the rates of those processes. Hillslopes that steepen up to certain critical thresholds are capable of shedding extremely large volumes of material very quickly, making hillslope processes an extremely important element of landscapes in tectonically active areas.<ref>{{cite journal |last1=Roering |first1=Joshua J. |last2=Kirchner |first2=James W. |last3=Dietrich |first3=William E. |title=Evidence for nonlinear, diffusive sediment transport on hillslopes and implications for landscape morphology |journal=[[Water Resources Research]] |date=March 1999 |volume=35 |issue=3 |pages=853–870 |doi=10.1029/1998WR900090 |bibcode=1999WRR....35..853R |doi-access=free }}</ref>

On the Earth, biological processes such as [[burrowing]] or [[tree throw]] may play important roles in setting the rates of some hillslope processes.<ref>{{cite journal |last1=Gabet |first1=Emmanuel J. |last2=Reichman |first2=O.J. |last3=Seabloom |first3=Eric W. |title=The Effects of Bioturbation on Soil Processes and Sediment Transport |journal=[[Annual Review of Earth and Planetary Sciences]] |date=May 2003 |volume=31 |issue=1 |pages=249–273 |doi=10.1146/annurev.earth.31.100901.141314 |bibcode= 2003AREPS..31..249G}}</ref>

=== Igneous processes ===
Both [[volcanic]] (eruptive) and [[plutonic]] (intrusive) igneous processes can have important impacts on geomorphology. The action of volcanoes tends to rejuvenize landscapes, covering the old land surface with [[lava]] and [[tephra]], releasing [[pyroclastic flow|pyroclastic]] material and forcing rivers through new paths. The cones built by eruptions also build substantial new topography, which can be acted upon by other surface processes. Plutonic rocks intruding then solidifying at depth can cause both uplift or subsidence of the surface, depending on whether the new material is denser or less dense than the rock it displaces.

=== Tectonic processes ===
{{See also|Erosion and tectonics}}
[[Plate tectonics|Tectonic]] effects on geomorphology can range from scales of millions of years to minutes or less. The effects of tectonics on landscape are heavily dependent on the nature of the underlying [[bedrock]] fabric that more or less controls what kind of local morphology tectonics can shape. [[Earthquake]]s can, in terms of minutes, submerge large areas of land forming new wetlands. [[Isostatic rebound]] can account for significant changes over hundreds to thousands of years, and allows erosion of a mountain belt to promote further erosion as mass is removed from the chain and the belt uplifts. Long-term plate tectonic dynamics give rise to [[orogeny|orogenic belts]], large mountain chains with typical lifetimes of many tens of millions of years, which form focal points for high rates of fluvial and hillslope processes and thus long-term sediment production.

Features of deeper [[Mantle (geology)|mantle]] dynamics such as [[mantle plume|plumes]] and [[delamination (geology)|delamination]] of the lower lithosphere have also been hypothesised to play important roles in the long term (> million year), large scale (thousands of km) evolution of the Earth's topography (see [[dynamic topography]]). Both can promote surface uplift through isostasy as hotter, less dense, mantle rocks displace cooler, denser, mantle rocks at depth in the Earth.<ref>{{cite journal |last1=Cserepes |first1=L. |last2=Christensen |first2=U.R. |last3=Ribe |first3=N.M. |title=Geoid height versus topography for a plume model of the Hawaiian swell |journal=[[Earth and Planetary Science Letters]] |date=15 May 2000 |volume=178 |issue=1–2 |pages=29–38 |doi=10.1016/S0012-821X(00)00065-0 |bibcode=2000E&PSL.178...29C}}</ref><ref>{{cite journal |last1=Seber |first1=Dogan |last2=Barazangi |first2=Muawia |last3=Ibenbrahim |first3=Aomar |last4=Demnati |first4=Ahmed |title=Geophysical evidence for lithospheric delamination beneath the Alboran Sea and Rif–Betic mountains |journal=[[Nature (journal)|Nature]] |date=29 February 1996 |volume=379 |issue=6568 |pages=785–790 |doi=10.1038/379785a0 |bibcode = 1996Natur.379..785S |url=http://ecommons.cornell.edu/bitstream/1813/5287/1/Seber1996_Abstract%26Figure.pdf |hdl=1813/5287 |s2cid=4332684 |hdl-access=free}}</ref>

=== Marine processes ===
Marine processes are those associated with the action of waves, marine currents and seepage of fluids through the seafloor. [[Mass wasting]] and submarine [[landslide|landsliding]] are also important processes for some aspects of marine geomorphology.<ref>Guilcher, A., 1958. Coastal and submarine morphology. Methuen.</ref> Because ocean basins are the ultimate sinks for a large fraction of terrestrial sediments, depositional processes and their related forms (e.g., sediment fans, [[deltas]]) are particularly important as elements of marine geomorphology.