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GGééomorphologie omorphologie quantitativequantitative
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True /False
1. Geomorphology is the study of process working on
landforms
2. Surface features of the earth were commonly attributed
to catastrophic events
3. Climate dominates landscape evolution
4. Most landscapes are Quaternary
5. There are simple explanations for most landforms
6. Enhanced erosion can drive uplift mountain summits
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Overview
What is Geomorphology ?
Relevance of Geomorphology
Development of Geomorphology
Terminology and definitions
Process Geomorphology
Some modern controversies
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What is geomorphology ?
GeomorphologyGê : Earth
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What is geomorphology ?
GeomorphologyGê : Earth
Morphê : Form
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What is geomorphology ?
GeomorphologyGê : Earth
Morphê : Form
Logos : Study
The study of landforms on or near the Earth’s surface and the processes working on them.
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Relevance of geomorphology
People live on landforms and their lives are affected (sometimes catastrophically) by geomorphic processes
Slope determines whether soil accumulates and makes arable land
Slope stability controls landslidesMountains drastically affect the
weather: rainshadows, monsoonsErosion-sedimentation have a
large impact on the carbon cycle
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Relevance of geomorphology
Human action is one of the major processes of geomorphic evolution
People have been building terraced hillsides for thousands of years
People dam rivers, drain groundwater, engineer coast-lines
People plant or burn vegetation on a huge scale
People are paving the worldPeople are changing the
climate
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What is geomorphology ?
Geomorphology relates to all the other disciplines of geology in two directions:
–Tectonics, petrology, geochemistry, stratigraphy, and climate determine the geomorphology of the earth and its regions by controlling the principal influences on landscape.
–Therefore evidence from observations of the landscape in turn constrain the tectonic, petrologic, geochemical, stratigraphic, and climatic history of the earth and its regions.
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What is geomorphology ?
Tectonic motions create geomorphic features like fault scarps and grabens; from observation of scarps and grabens we infer the sense of tectonic motions and something about their ages.
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What is geomorphology ?
Volcanic activity creates calderas; from the form of the caldera we learn about the mechanism of eruption.
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What is geomorphology ?
Granite weathers to rounded jointstones; from observation of the shape of boulders and outcrops we can quickly map granite plutons; from the shape of these rocks we infer how they joint and how they chemically weather
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What is geomorphology ?
Resistant and weak strata determine the shapes of cliffs; from distant observations of cliff shapes and local knowledge of stratigraphy, we can map outcrops as far as the eye can see
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What is geomorphology ?
Glacial processes create geomorphic expressions such as moraines; from the position, form, and age of the moraines we learn about paleoclimate and the nature of glaciers
Mapping the 1890 thrust moraine of Brúarjökull. Photo: Ólafur Ingólfsson 2004.
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What is geomorphology ?
Arid land geomorphology
Coastal geomorphology
Tectonic landforms
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What is geomorphology ?Fluvial processes and landforms
Karst processes and landforms
Eolian processes
Glacial erosion and landforms
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What is geomorphology ?Chemical
weathering and soils
Physical weathering
Mass movement and slopes
Drainage basins
Glaciers and glacial mechanisms ✔
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What is geomorphology ?Dating of geomorphic features
Field trip – Regional geomorphology
Landscape evolution modeling
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Géomorphologie
http://www.gm.univ-montp2.fr/spip/spip.php?article1004
Alfredo Taboada
Rodolphe Cattin
Jean-François Ritz
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Date Lieu Enseignement Horaire Enseignant
12/03 M2A Introduction 10h00-12h00 cours Cattin
13/03 M2A Processus de versant 9h00-12h00 cours Cattin
14/03 M2A Instabilité de pente 9h00-12h00 cours Taboada
15/03 Bat 22 1er salle info Modélisation 9h00-12h00 Cattin
19/03 M2A Dynamique des rivières 9h00-12h00 cours Cattin
20/03 M2A Incision fluviale 9h00-12h00 cours Cattin
22/03 Case Courrier Cattin Remise du devoir 18h00
26/03 M2A Diffusion 9h00-12h00 TD Taboada
28/03 M2A Morphotectonique 9h00-12h00 cours Ritz
3-4-5/04
St Bauzille-de-Putois
Sorties terrain - Photo Aérienne et Carte
Cattin Ritz Taboada
16/04 Bureau Cattin Remise du rapport 18h00
18/04 M2A Examen 2h
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Development of Geomorphology
In the 17th & early 18th century, surface features of the earth were commonly attributed to catastrophic, often biblical-like events; A school of thought referred to as "catastrophism"
Georges Cuvier, 1768-1832
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Development of Geomorphology
During the late 18th & 19th century, the works of Hutton, Playfair, & Lyell introduced the concept of“uniformitarianism”: "the present is the key to the past."
James Hutton, 1726-1797. Sir Charles Lyell, 1797-1875 John Playfair, 1748-1819
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Development of Geomorphology
By the late 19th century, Gilbert postulated that landforms reflect a state of balance between the processes that actupon them and the structure and composition of the rocks that compose them
Grove Karl Gilbert, 1843 - 1918 Terraces marking former strand lines of Lake Bonneville on hillside atBonneville Salt Flats, western Utah. Image date Oct. 2006
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Development of Geomorphology
But geomorphologists were “lured away”by the Davisian model of landform development
William Morris Davis, 1850-1934
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Development of Geomorphology
In Davis’s models tectonic forcing is an impulsive event that occurs at the beginning of the “geomorphic cycle”.
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Development of Geomorphology
Walther Penck , 1888-1923
Penck suggested a more wave-likepattern of tectonic forcing through time
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Development of Geomorphology
John Hack proposed that, when rate of deformationare sustained for a long intervals, landscapes willcome into a sort of balance or dynamic equilibrium.
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Development of Geomorphology
By the mid 20th century, there was a return to theimportance of the relationship between form and process, fuelled in large part by the “quantitative revolution”.
A. Faraud Mountain, Dévoluy, SE France. B. Associatedexperimental modeling (Bonnet & Crave, Geology, 2003)
A
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Terminology and definition
Agents“that which acts or has the power to act”Water, wind, ice…
Processes“progressive steps by which an end is attained”Weathering, erosion, transport, deposition
EnergySolar, geothermal, gravitational, chemical
Systems“an assemblage of parts forming a whole”Fluvial, glacial, coastal
ClimateDetermines dominant agents
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Terminology and definition
TimeEvolution of landforms/landscapes
ThresholdA condition that must be exceeded in order for state to change within the system
FeedbackPositive – self-reinforcing; acceleratingNegative – self-regulating; damping
EquifinalitySimilar final states achieved through different mechanisms
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Terminology and definition
Steady-stateA time-invariant condition
Dynamic equilibriumState changes around a central point
Change
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Process Geomorphology
The concept of “dynamic equilibrium” was re-born, as landforms were seen as adjusting to the processes operating on the geology and consequently, processand form share a “cause and effect relationship”. The emphasis on “form and process” led to the development of “Process Geomorphology”.
ExogenicprocessesWeathering,
transport, erosion, sedimentation
Endogenic processesTectonic, isostasy
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Process Geomorphology
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Process Geomorphology
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Process Geomorphology
A delicate balance or equilibrium exists between landforms and process.
The perceived balance between process and form is created by the interaction of energy, force, and resistance.
Changes in the balance between driving and resisting forces may destabilize the system. The system may cross a threshold, and may initiate a new pattern of equilibrium.
Various processes are linked in such a way that the effect of one process may initiate the action of another
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Process Geomorphology
A delicate balance or equilibrium exists between landforms and process.
Main drainage basins in France
Main drainage basins in Hérault
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Process Geomorphology
A delicate balance or equilibrium exists between landforms and process.
Geomorphic elements of a drainage basin, Burbank & Anderson, 2001
• River channels• Hillslopes• Crests of interfluves• Drainage divide
Some of theseelements will respondmore rapidly to changes imposed on them than will others
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Process Geomorphology
The perceived balance between process and form is created by the interaction of energy, force, and resistance.
Force F = m aweight = mass * gravityA measurement of force is Newton
Energy (or work) = force*distance = mass *gravity *htF * d m * a *ht
A measurement of energy is Joules
Driving Forces: Climate, Gravity, Forces generated inside the earthResistance: Provided by the geologic framework
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Process Geomorphology
Changes in the balance between driving and resisting forces may destabilize the system. The system may cross a threshold, and may initiate a new pattern of equilibrium.
Thresholds Changes in the geomorphic system when the limits of equilibrium are exceededa. Extrinsic Thresholds: caused by external controlling factorsb. Intrinsic Thresholds: usually caused by internal factors.
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Process Geomorphology
Changes in the balance between driving and resisting forces may destabilize the system. The system may cross a threshold, and may initiate a new pattern of equilibrium.
Before After
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Process GeomorphologyVarious processes are linked in such a way that the
effect of one process may initiate the action of another
Gabet et al., Geomorphology, 2004Burtin et al., JGR, 2009
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Process Geomorphology
Processes are multivariate and interrelated
Different time frames for the study of geomorphic
systems
Complexities: Thresholds, stores, non-linear
relationships, multiple relationships
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Some modern controversies
Philip England
Peter Molnar
P. Molnar and P. C. England. Late Cenozoic uplift of mountain ranges and global climate change: chicken or egg. Nature, 346:29-34, 1990
How do we tell whether the climate caused uplift of the summits or whether surface uplift of the ranges causedchanges in climate ?
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Some modern controversies
How do you determine mean elevation in the past ?During Ice Age time, was there more precipitation or less ?Can enhanced erosion drive uplift of montain summits ?
Burbank & Anderson, 2001
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Some modern controversies
What controls the ultimate height of mountains ?Are surface processes capable of eroding at several
mm/yr ?Or rapid rates of rock uplift are commonly compensated by
events of tectonics erosion (extensional faulting) ?
Comparison between the heights of Mt. Everest on Earth, Maxwell Montes on Venus and Olympus Mons on Mars
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References
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True /False
1. Geomorphology is the study of process working on
landforms
2. Surface features of the earth were commonly attributed
to catastrophic events
3. Climate dominates landscape evolution
4. Most landscapes are Quaternary
5. There are simple explanations for most landforms
6. Enhanced erosion can drive uplift mountain summits
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