GEOMORPHOLOGY - BASICS

WHAT IS GEOMORPHOLOGY

Study of Earths Physical land surface features, its landforms—rivers, hills, plains, beaches, sand dunes and myriad others
Genetic study of Topographic forms

Process or functional Geomorphology -- relationship between Landforms & process acting on them now

Applied Geomorphology -- Geomorphic process & human history

Historical Geomorphology -- History & current form is not a function of current process

Structural Geomorphology – Geological structures related to geomorphology

Climatic Geomorphology --Climate exerts influence on landforms

Historical Geomorphology --landscape history by mapping morphological & sedimentary features

William Morris Davis --

Uplift takes place
Raw topography worn down by geomorphic process

Topography reduced to flat region close to base level – peneplain with occasional hills called monad nocks Young, mature, old age

Walter Penck –Uplift & denudation takes place at the same time

Convex Slope Profile - uplift >denudation
Straight slope profiles – denudation = uplift
Concave slope profile - uplift <>

Process geomorphology

Study of processes related to landform development

Grove Karl Gilbert

- Database of process rates in various parts of the globe
- Built increasingly refined models for predicting the short term
- Generated powerful ideas about stability and instability in geomorphic systems

Modelling geomorphic processes – construction of models for predicting short term changes in landform

Applied geomorphology

Interaction of humans with landforms and landscapes

Form

Two main approaches

- Field description and morphological mapping
- Mathematical representation 9geomorphometry)

Field Description and morphological Mapping

Field description, field sketching, map reading & map making

Mapping of landforms –
References: Dackombe & Gardiner 1983
Evans 1994

Morphological mapping

Identifies basic landform features in field, on aerial photographs, on maps
Landform elements – Curved geometrical surfaces lacking inflections
(complicated kinks) Relationship with upslope, downslope, lateral elements

Facets, sites, land elements, terrain components, facies
Site – elaboration of facet
Involves altitude, extent, slope, curvature, ruggedness and relationship with water tube
DEM – Digital Elevation Model

Geomorphometry

Studies quantitatively the form of the land surface, remote sensing images and GIS
Terrain Analysis & Surface modelling
- Morphometry of continental ice surface
- Characterizing glacial troughs
- Mapping sea floor terrain types
- Mapping ecoegions

DEM

Electronic distance measurement (EDM) in surveying
Global positioning system – GPS

Digital elevation model (DEM)
Digital Terrain Model (DTM) – ordered array of numbers that represent the spatial distribution of elevations above some arbitary datum in landscape

DEM is a subset of DTM

Geomorphic System

Systems approach – define a system of the landform for identification of elements

Reconstructing Geomorphic history

Dating techniques

For researches of past landscape

Archives of past environmental condition
Tree-rings, lake sediments, polar ice cores, midlatitude ice cores, coral deposits coral deposits, loess, ocean cores, pollen, palaesols, sedimentary rocks and historical method

Contribution of geomorphology towards Global Environmental Change

Reference: Geomorphology: Human Activity and Global Environmental Change by Olav Slaymaker

Sideral Method (annual method)

Dendrochronology – 0-5000 years – Growth rings of live trees or correlating ring width chronology with other trees
Geomorphic method – 2000 -20000 years – progressive change in scrap profile (From steep and angular to gentle rounded) – Fault scrap and other landforms with scrap like features (Terraces)

Land Chronosequence (historical geomorphology)

Spatial sequence of landforms
Topographic chronosequence, space-time substitution

Question of Scale

As scale increases, explanation of their behaviour changes

Stanley A Schumn resolved scale problem by providing linkage between historical & process geomorphology
Larger scale landforms explained by historical geomorphology
Older & bigger landform – less accurate prediction from present form

GEOMORPHOLOGY:

Study of Landform
3 Key elements – Landform
Geomorphic Process
Land-surface History

Form described by morphological maps and morphometry

Reference: Geomorphological Techniques. A.S. Goudie

GEOMORPHIC SYSTEM

Main Mechanism	Water Content
	Very Low	Low	Moderate	High	Very High	Extremely High
Creep		Rock Creep Continuous Creep
Flow	Dry Flow	Slow Earth Flow Debris Avalanche (Struzstiorm) Snow Avalanche (slab avalanche) Sluff (Small loose snow Avalanche)		Solifluction Gelifluction Debris Flow	Rapid Earth Flow Rainwas Sheetwash	Mudflow Slush Avalanche Ice Flow Rill wash River flow lake currents
Slide (translational)		Debris slide earh slide debris block slide earth block slide rock slide rock block slide	Debris slide earh slide debris block slide earth block slide		Rapids (in part) Ice Sliding
Slide (Rotational)		Rock Slump	Debris Slump Earth Slump
Heave		Soil Creep Talus Creep
Fall		Rockfall Debris fall Earth falll				Waterfall Icefall
Subsidence		Cavity Collapse Settlement

Mass Movements

1. Rock Creep & Continuous Creep

Slow plastic deformation of soil and rock. Result from stress applied by the weight of the soil or rock body and usually occur at depth below the weather mantle, not same as soil creep

2. Flow

Shear through the soil, rock or snow and ice debris, rate is slow at base and increases towards the surface, turbulent motion

a. Avalance – rapid down slope movement of earth, rock, ice, snow
b. Debris flow/ Earth flow/ mudflow – snow & ice, rock debris, sandy material, clay
c. Solifluction & gelifluction – downward movement of saturated soil, downslope movement over permanently frozen subsoil
d. Debris flow – fast moving body of sediments & particles with water & air or both
e. Mudflow –

3. Slides: Widespread form of mass movement along clearcut shear planes, 10 times longer than width

a. Translational slides – occurring along planar shear planes and includes debris slide, earth slide, earthblock slide, rock slide and rock block slide

b. Rotational slides or slumps – along concave shear planes, low to moderate water content include rock slump, debris slump and earth slump

4. Heave – Produced by alternating process of expansion and contraction, heating & cooling, wetting & drying and by burrowing of animals

Soil creep – finer material
Talus creep – coarse material
Frost Creep – freeze-thaw action
Terracettes – grassy slopes

5. Fall – Downward movement of rock and soil, rockfall, debrisfall, earthfall

6. Subsidence – Cavity Collapse – rock and soil plummets into underground surface
Settlement – Lowered Progressively by compaction

Sediments

Clastic sediments (detrital sedimets)

- Formed though roch weatheringaccumulate insitu in form of regolith
- Transported by a fluid medium (air, water, Ice)
- Grouped according to size

o Rudaceous sediments – coarse loose fragments, comprise of boulders, pebbles, cobbles, granules, glacial till (2mm or more)

o Arenaceous Deposits (2 - .0625mm ) – Sands

o Argillaceous deposits (<.0625 mm)

· Silt – 0.0625 – 0.002

· Clay - <0.002>

Chemical Sedimets

- Releases mineral matter in solution
- Takes place insitu
- Iron oxides and hydroxides – precipitate on sea floor as chamosite, green iron silicate
- Calcium carbonate – in caves & grottoes Stalagmites, stalactites, colums of dripstone
- Evaporate – soluble salt precipitation in low-lying land areas and inland seas
- Dericrusts – precipitated in soil and sediments

Biogenic sediment

- Incorporated in organic body and accumulates after organisms die
- Chalk, dolomite, siliceous deposits, organic muds, peat
- Dy – gelationous acidic sediments formed in humic lakes and ponds
- Gyttja – Biologically produced sedimentary oozes.

SOURCE:

FUNDAMENTALS OF GEOMORPHOLOGY
RICHARD JOHN HUGGETT