This document provides an overview of structural geomorphology and the key surface and subsurface processes that shape the Earth's landscapes. It discusses global geomorphology and the intersection between climatic, hydrologic, and biologic surface processes with underlying geologic processes. Specific topics covered include plate tectonics and the different landforms that form at divergent, convergent and transform plate boundaries. The document also discusses weathering processes, the factors that influence them, and characteristic landforms formed by weathering such as exfoliation domes and rock basins. Finally, it covers slope stability and the different types of landslides that can occur based on material type and movement.
This is my presentation on the tectonic control of sediments.
It includes the effects of tectonics either direct or indirect on sediments and sedimentation.
Sedimentation along various plate boundaries.
Few examples as evidence from Pakistan (the Siwalik Group) and Argentina (Fiambala Basin)
Lecture 4 Outline Plate Tectonics – Mechanisms and MarginsL.docxSHIVA101531
Lecture 4 Outline:
Plate Tectonics – Mechanisms and Margins
Learning Objectives:
What are the types of plate boundaries?
What processes occur at different types of plate boundaries?
What are hotspots?
How does tectonics build continents and ocean basins?
What Happens at Plate Boundaries?
Plate interiors stable - geologic activity limited to surface processes
But interactions between plates at plate boundaries results in
Magma and volcanism
Faulting and earthquakes
Mountain building
Production of new crust
Recycling of old crust
What are the Types of Plate Boundaries?
Divergent
plates pulled apart
Convergent
plates collide
Transform
plates sheared
Each plate surrounded by different types of boundaries
What are the Types of Plate Boundaries?
What are Divergent Plate Boundaries?
Ridges
Crust pulled apart
Magma by decompression melting in asthenosphere
Cools to make new oceanic crust
Oceanic crust
lithosphere
asthenosphere
magma
central rift valley
faults
North Atlantic Ridge
Mid-Atlantic Ridge
East Pacific Ridge
Indian Ridge
Antarctic Ridge
Where are Divergent Plate Boundaries Found?
Ocean ridge above sea level in Iceland
Where are Divergent Plate Boundaries Found?
What are the Major Geologic Features of the Ocean Ridge?
Shield Volcano
Edge of North American Plate
Fault
Down-dropped fault block
Central rift valley
Filled by lava flows
What are Convergent Plate Boundaries?
Two plates collide with each other – two types
Subduction zone
Between two plates of different density - denser plate subducted
melting in mantle by addition of water from subducted plate
Trench and volcanic arc - chain of volcanoes on overriding plate
Earthquakes
What are Convergent Plate Boundaries?
Collision zone
between plates too buoyant to subduct
Crust thickened and mountains raised instead
Earthquakes but no volcanoes
Indian Plate
Eurasian Plate
Younger and weaker
Older and stronger
deformed
Which Plate gets Subducted?
If both plates composed of oceanic crust
older and denser crust subducted by younger and lighter crust
Overriding plate
Plate boundary
Where Can We Find an Example of an Oceanic Plate Subducted by Another Oceanic Plate?
Pacific Plate subducted by Philippine Plate at Mariana Trench
Pacific Plate
(older)
Philippine Plate
(younger)
Japan Trench
Mariana Trench
Challenger Deep
Eurasian Plate
Which Plate gets Subducted?
If one plate of continental crust and one of oceanic crust
denser oceanic crust subducted by lighter continental crust
Material too light to subduct added to continent as accreted terranes
sediments, volcanic islands, fragments of continental crust
Where Can We Find an Example of a Collision Zone?
Indian and Eurasian Plates
Collision began 45 mya when subduction completely closed ocean basin
Himalaya and Tibetan Plateau
Recent or continuing collisions produce Earth’s tallest mountains
50 mya
today
Closing Ocean
Spreading Ocean
14
Oblique motion betw ...
This is my presentation on the tectonic control of sediments.
It includes the effects of tectonics either direct or indirect on sediments and sedimentation.
Sedimentation along various plate boundaries.
Few examples as evidence from Pakistan (the Siwalik Group) and Argentina (Fiambala Basin)
Lecture 4 Outline Plate Tectonics – Mechanisms and MarginsL.docxSHIVA101531
Lecture 4 Outline:
Plate Tectonics – Mechanisms and Margins
Learning Objectives:
What are the types of plate boundaries?
What processes occur at different types of plate boundaries?
What are hotspots?
How does tectonics build continents and ocean basins?
What Happens at Plate Boundaries?
Plate interiors stable - geologic activity limited to surface processes
But interactions between plates at plate boundaries results in
Magma and volcanism
Faulting and earthquakes
Mountain building
Production of new crust
Recycling of old crust
What are the Types of Plate Boundaries?
Divergent
plates pulled apart
Convergent
plates collide
Transform
plates sheared
Each plate surrounded by different types of boundaries
What are the Types of Plate Boundaries?
What are Divergent Plate Boundaries?
Ridges
Crust pulled apart
Magma by decompression melting in asthenosphere
Cools to make new oceanic crust
Oceanic crust
lithosphere
asthenosphere
magma
central rift valley
faults
North Atlantic Ridge
Mid-Atlantic Ridge
East Pacific Ridge
Indian Ridge
Antarctic Ridge
Where are Divergent Plate Boundaries Found?
Ocean ridge above sea level in Iceland
Where are Divergent Plate Boundaries Found?
What are the Major Geologic Features of the Ocean Ridge?
Shield Volcano
Edge of North American Plate
Fault
Down-dropped fault block
Central rift valley
Filled by lava flows
What are Convergent Plate Boundaries?
Two plates collide with each other – two types
Subduction zone
Between two plates of different density - denser plate subducted
melting in mantle by addition of water from subducted plate
Trench and volcanic arc - chain of volcanoes on overriding plate
Earthquakes
What are Convergent Plate Boundaries?
Collision zone
between plates too buoyant to subduct
Crust thickened and mountains raised instead
Earthquakes but no volcanoes
Indian Plate
Eurasian Plate
Younger and weaker
Older and stronger
deformed
Which Plate gets Subducted?
If both plates composed of oceanic crust
older and denser crust subducted by younger and lighter crust
Overriding plate
Plate boundary
Where Can We Find an Example of an Oceanic Plate Subducted by Another Oceanic Plate?
Pacific Plate subducted by Philippine Plate at Mariana Trench
Pacific Plate
(older)
Philippine Plate
(younger)
Japan Trench
Mariana Trench
Challenger Deep
Eurasian Plate
Which Plate gets Subducted?
If one plate of continental crust and one of oceanic crust
denser oceanic crust subducted by lighter continental crust
Material too light to subduct added to continent as accreted terranes
sediments, volcanic islands, fragments of continental crust
Where Can We Find an Example of a Collision Zone?
Indian and Eurasian Plates
Collision began 45 mya when subduction completely closed ocean basin
Himalaya and Tibetan Plateau
Recent or continuing collisions produce Earth’s tallest mountains
50 mya
today
Closing Ocean
Spreading Ocean
14
Oblique motion betw ...
Study of plate tectonics of the earth, or plate movement, Jahangir Alam
a) Wegener’s Evidence (Continental Drift)
b) History of Plate Tectonics
c) Breakup and Appearence of Pangea
WHAT IS A PLATE?
Major continental and oceanic plates include:
Types of Earth’s Crust:
Plate tectonics (from the Late Latin tectonicus) is a scientific theory which describes the large scale motions of Earth's lithosphere.
THE DYNAMIC EARTH:
The earth is a dynamic planet, continuously changing both externally and internally. The earth’s surface is constantly being changed by endo-genetic processes resulting in volcanism and tectonism, and exogenetic processes such as erosion and deposition. These processes have been active throughout geological history. The processes that change the surface feature are normally very slow (erosion and deposition) except some catastrophic changes that occur instantaneously as in the case of volcanism or earthquakes. The interior of the earth is also in motion. Deeper inside the earth, the liquid core probably flows at a geologically rapid rate of a few tenths of mm/s. Several hypotheses attempted to explain the dynamism of the earth.
+ Horizontal movement hypothesis
+ Continental drift, displacement hypothesis
Development of the plate tectonic theory.
Plate tectonic theory arose out of the hypothesis of continental drift proposed by Alfred Wegener in 1912. He suggested that the present continents once formed a single land mass that drifted apart, thus releasing the continents from the Earth's core and likening them to "icebergs" of low density granite floating on a sea of denser basalt.
Seafloor Spreading
The first evidence that the lithospheric plates did move came with the discovery of variable magnetic field direction in rocks of differing ages.
Study of plate tectonics of the earth, or plate movement, Jahangir Alam
a) Wegener’s Evidence (Continental Drift)
b) History of Plate Tectonics
c) Breakup and Appearence of Pangea
WHAT IS A PLATE?
Major continental and oceanic plates include:
Types of Earth’s Crust:
Plate tectonics (from the Late Latin tectonicus) is a scientific theory which describes the large scale motions of Earth's lithosphere.
THE DYNAMIC EARTH:
The earth is a dynamic planet, continuously changing both externally and internally. The earth’s surface is constantly being changed by endo-genetic processes resulting in volcanism and tectonism, and exogenetic processes such as erosion and deposition. These processes have been active throughout geological history. The processes that change the surface feature are normally very slow (erosion and deposition) except some catastrophic changes that occur instantaneously as in the case of volcanism or earthquakes. The interior of the earth is also in motion. Deeper inside the earth, the liquid core probably flows at a geologically rapid rate of a few tenths of mm/s. Several hypotheses attempted to explain the dynamism of the earth.
+ Horizontal movement hypothesis
+ Continental drift, displacement hypothesis
Development of the plate tectonic theory.
Plate tectonic theory arose out of the hypothesis of continental drift proposed by Alfred Wegener in 1912. He suggested that the present continents once formed a single land mass that drifted apart, thus releasing the continents from the Earth's core and likening them to "icebergs" of low density granite floating on a sea of denser basalt.
Seafloor Spreading
The first evidence that the lithospheric plates did move came with the discovery of variable magnetic field direction in rocks of differing ages.
"Understanding the Carbon Cycle: Processes, Human Impacts, and Strategies for...MMariSelvam4
The carbon cycle is a critical component of Earth's environmental system, governing the movement and transformation of carbon through various reservoirs, including the atmosphere, oceans, soil, and living organisms. This complex cycle involves several key processes such as photosynthesis, respiration, decomposition, and carbon sequestration, each contributing to the regulation of carbon levels on the planet.
Human activities, particularly fossil fuel combustion and deforestation, have significantly altered the natural carbon cycle, leading to increased atmospheric carbon dioxide concentrations and driving climate change. Understanding the intricacies of the carbon cycle is essential for assessing the impacts of these changes and developing effective mitigation strategies.
By studying the carbon cycle, scientists can identify carbon sources and sinks, measure carbon fluxes, and predict future trends. This knowledge is crucial for crafting policies aimed at reducing carbon emissions, enhancing carbon storage, and promoting sustainable practices. The carbon cycle's interplay with climate systems, ecosystems, and human activities underscores its importance in maintaining a stable and healthy planet.
In-depth exploration of the carbon cycle reveals the delicate balance required to sustain life and the urgent need to address anthropogenic influences. Through research, education, and policy, we can work towards restoring equilibrium in the carbon cycle and ensuring a sustainable future for generations to come.
Artificial Reefs by Kuddle Life Foundation - May 2024punit537210
Situated in Pondicherry, India, Kuddle Life Foundation is a charitable, non-profit and non-governmental organization (NGO) dedicated to improving the living standards of coastal communities and simultaneously placing a strong emphasis on the protection of marine ecosystems.
One of the key areas we work in is Artificial Reefs. This presentation captures our journey so far and our learnings. We hope you get as excited about marine conservation and artificial reefs as we are.
Please visit our website: https://kuddlelife.org
Our Instagram channel:
@kuddlelifefoundation
Our Linkedin Page:
https://www.linkedin.com/company/kuddlelifefoundation/
and write to us if you have any questions:
info@kuddlelife.org
Natural farming @ Dr. Siddhartha S. Jena.pptxsidjena70
A brief about organic farming/ Natural farming/ Zero budget natural farming/ Subash Palekar Natural farming which keeps us and environment safe and healthy. Next gen Agricultural practices of chemical free farming.
Micro RNA genes and their likely influence in rice (Oryza sativa L.) dynamic ...Open Access Research Paper
Micro RNAs (miRNAs) are small non-coding RNAs molecules having approximately 18-25 nucleotides, they are present in both plants and animals genomes. MiRNAs have diverse spatial expression patterns and regulate various developmental metabolisms, stress responses and other physiological processes. The dynamic gene expression playing major roles in phenotypic differences in organisms are believed to be controlled by miRNAs. Mutations in regions of regulatory factors, such as miRNA genes or transcription factors (TF) necessitated by dynamic environmental factors or pathogen infections, have tremendous effects on structure and expression of genes. The resultant novel gene products presents potential explanations for constant evolving desirable traits that have long been bred using conventional means, biotechnology or genetic engineering. Rice grain quality, yield, disease tolerance, climate-resilience and palatability properties are not exceptional to miRN Asmutations effects. There are new insights courtesy of high-throughput sequencing and improved proteomic techniques that organisms’ complexity and adaptations are highly contributed by miRNAs containing regulatory networks. This article aims to expound on how rice miRNAs could be driving evolution of traits and highlight the latest miRNA research progress. Moreover, the review accentuates miRNAs grey areas to be addressed and gives recommendations for further studies.
UNDERSTANDING WHAT GREEN WASHING IS!.pdfJulietMogola
Many companies today use green washing to lure the public into thinking they are conserving the environment but in real sense they are doing more harm. There have been such several cases from very big companies here in Kenya and also globally. This ranges from various sectors from manufacturing and goes to consumer products. Educating people on greenwashing will enable people to make better choices based on their analysis and not on what they see on marketing sites.
WRI’s brand new “Food Service Playbook for Promoting Sustainable Food Choices” gives food service operators the very latest strategies for creating dining environments that empower consumers to choose sustainable, plant-rich dishes. This research builds off our first guide for food service, now with industry experience and insights from nearly 350 academic trials.
2. Global geomorphology
• Geomorphology: The study of surface landforms,
processes and landscape evolution of the Earth.
• The surface of Earth is modified by a combination of
surface processes that shape landscapes, and geologic
processes that cause tectonic uplift and subsidence.
Surface processes comprise;
• the action of water, wind, ice, fire, and living things
• the stability and rate of change of topography under the
force of gravity, and
• human alteration of the landscape.
Many of these factors are strongly mediate by climate.
3. Cont’d
• Geologic processes include:
the uplift of mountain ranges,
the growth of volcanoes,
isostatic changes in land surface elevation
the formation of deep sedimentary basins
where the surface of Earth drops and is filled
with material eroded from other parts of the
landscape.
• The Earth surface and its topography therefore
are an intersection of climatic, hydrologic, and
biologic action with geologic processes.
4. Cont’d
• The broad-scale topographies of Earth illustrate
this intersection of surface and subsurface action.
• Mountain belts are uplifted due to geologic
processes.
• Denudation of these high uplifted regions
produces sediment that is transported and
deposited elsewhere within the landscape or off
the coast.
• On progressively smaller scales, similar ideas
apply, where individual landforms evolve in
response to the balance of additive processes
(uplift and deposition) and subtractive processes
(subsidence and erosion).
5. Cont’d
Geomorphically, relevant processes generally fall into;
1) the production of regolith by weathering and erosion,
2) the transport of that material, and
3) its eventual deposition.
Although there is a general movement of material
from uplands to lowlands, erosion, transport, and
deposition often occur in closely spaced cycle all across
the landscape.
Primary surface processes responsible for most
topographic features include wind, waves, chemical
dissolution, mass wasting, groundwater movement,
surface water flow, glaciations.
Other more exotic geomorphic processes might include
freeze-thaw processes, salt-mediated action, or
extraterrestrial impact.
6. Processes and Landforms associated with
Plate margins
• What is plate tectonics
• The theory of plate tectonics proposes that the lithosphere is
divided into eight major plates (North American, South
American, Pacific, Nazca, Eurasian, African, Antarctic, and
Indian-Australian) and several smaller plates (e.g., Arabian,
Scotia, Juan de Fuca).
• These plates are mobile, moving in constant, slow motion
measured in rates of centimeters per year.
• The plate motion is driven by one or more of the following
mechanisms:
1. Convection -- heat transferred by movement of a fluid
(magma)
2. Conduction -- heat transfer by touching plates
3. Push-Pull Slab -- heavy slabs pull plates downward and
magma forced upward pushes plates to the surface (upwelling)
7.
8. Plate Boundaries
• There are three general types of plate boundaries:
divergent, convergent, and transform.
1) Divergent
Where tension forces are pulling the earth’s plates
apart. (where plates move away from each other)
2) Convergent
Where compression forces push the earth’s plates
together (where plates crash into each other)
3) Transform:
Where shearing forces cause the earth’s plates to slide
past each other. (where plates rub against each other in
opposite directions)
Different Plate Boundaries Create Different Landforms
and Events:
9. 1) Landforms formed due to Divergent plate
boundaries
a) Two continental plates (CP) move away from
each other, stretching out the crust, until it
begins to break/fault.
• As crust is stretched wider, the valley drops
deeper.
• Eventually can lead to the creation of a new
body of water if low enough.
10.
11. Cont’d
b) Two oceanic plates (OP) move away from
each other, allowing magma to rise up from
inside the Earth.
The magma reaches the bottom of the
ocean, turns in to lava and cools (forming
new rock).
This cycle continues constantly spreading the
sea floor and adding new material along this
chain of mountains.
Sea Floor spreading occurs at these mid-
ocean ridges.
12.
13. 2) Landforms formed due to Convergent
plate boundaries
• Convergent boundaries come in three
varieties depending upon the type of
lithosphere that is juxtaposed across a
subduction zone.
a) Oceanic Plate vs. Oceanic Plate
Convergence
b) Continental Plate vs. Continental Plate
Convergence
c) Oceanic Plate vs. Continental Plate
Convergence
14. a) Oceanic Plate vs. Oceanic Plate Convergence.
• The older of the two plates descends into the
subduction zone when plates of oceanic lithosphere
collide along a trench.
• The descending plate carries water-filled sediments
from the ocean floor downward into the mantle.
• The presence of water alters the physical and chemical
conditions necessary for melting and causes magma
to form. The magma rises up through the overriding
oceanic plate, reaching the surface as a volcano.
• As the volcano grows, it may rise above sea level to
form an island. Trenches often lie adjacent to chains
of islands (island arcs) formed by magma from the
subducted plate.
15.
16. b) Continental Plate vs. Continental Plate
Convergence
continental plate is not dense enough to subduct.
As a result, the continental crust folds upward
(nowhere else to go) creating a chain of folded
mountains.
The tallest mountains in the world were formed
(and continue to grow) as a result of continental
collision. The Himalayan mountains mark the
boundary between the Indian and Eurasian plates.
17.
18. c) Oceanic Plate vs. Continental Plate Convergence
• As the more dense oceanic plate (OP) subducts
under the less dense continental plate (CP), it
pulls the front edge of the less dense plate down,
creating a deep ‘zone’.
• As a result, the deep-ocean trench landform is
formed.
• The more dense oceanic plate (OP) subducts under
the less dense continental plate (CP) and is driven
down in to the hot asthenosphere/mantle.
19. • Subducted plate melts due to extreme heat and
friction.
• Melted plate rises up through the crust, where it
reaches the surface and cools.
• Happens repeatedly to create large volcanoes.
• Convergence between these plates has resulted
in the formation of the Andes Mountains (the
second highest mountain range on Earth),
extensive volcanism, and widespread
earthquake activity. The largest earthquakes
are concentrated along subduction zones.
20.
21. 3) Landforms associated with Transform
Plate Boundaries
• Transform plate boundaries are the
underappreciated members of the plate
tectonics machine.
• New lithosphere is not created at transform
boundaries, neither is old lithosphere
destroyed;
• consequently, these boundaries are sometimes
termed conservative plate boundaries.
• The San Andreas Fault, California, is a
transform boundary that separates the North
American and Pacific Plates.
22. Mineral Stability and Weathering
Mineral Stability Series
• minerals are most stable at the temperature and pressure at
which they form.
• In the case of the igneous rock minerals described in
Bowen's Reaction Series, the higher temperature minerals
(such as olivine, pyroxene, etc.), when exposed at the
surface, will be farthest from their comfort zone, and will
therefore chemically weather at a faster rate.
• Quartz, at the other end of Bowen's, is closer to its
preferred temperature and should therefore be more
stable (and it is). This is one reason why we find quartz
sand at the beach, instead of olivine sand.
23.
24. What is weathering?
• Is decomposition and disintegration of rocks by chemical,
physical, and biological processes.
• Weathering breaks rocks into smaller pieces. It is the
effect of rainfall and temperature on rocks. Weathering
occurs in situ. This means the rocks stay in the same place
and are not moved.
• This is different from erosion. Erosion is when rocks are
moved around or hit by something moving so that they
break into smaller pieces.
Weathering
25. Rocks can be weathered in three ways:
1. Physical (Mechanical):
Large rocks broken into smaller fragments with no change
in composition frost wedging, exfoliation, root wedging,
running water and glacial abrasion, solar heating.
2. Chemical: chemical alteration or decomposition of rocks
and minerals.
Rocks dissolved - chemical and mineralogical composition
can be altered new minerals may form.
3. Biological Weathering: plants & animals
• Chemical (organic acids) and Physical (burrowing)
26. Factors that Influence Weathering
• Weathering of geologic material is determined
by:
• Rock type, structure
• Climate (Temperature, rainfall)
• Topography
• Time
27.
28. LANDFORMS RESULTING FROM WEATHERING
• Some characteristic landforms resulting from
mechanical and chemical weathering include:
• Exfoliation (and exfoliation domes)
• Spheroidal weathering forms
• Talus slopes
• Karst landforms
29. Cont’d
• Two groups of weathering landforms are:
(1)large-scale cliffs and pillars and
(2) smaller-scale rock-basins, tafoni and
honeycombs.
Cliffs and pillars
• are associated with several rock types,
including limestones and sandstones.
• Throughout the world, sandstone cliffs and
pillars are distinctive features of sandstone
terrain.
30. Cont’d
• Rock-basins, tafoni, and honeycombs
• Virtually all exposed rock outcrops bear irregular
surfaces that seem to result from weathering.
• Flutes and runnels, pits and cavernous forms are
common on all rock types in all climates.
• Rock-basins, also called weathering pits, weather
pits or gnammas, are closed, circular, or oval
depressions, a few centimetres to several metres
wide, formed on flat or gently sloping surfaces of
limestones, granites, basalts, gneisses, and other
rock types.
• They are commonly flat-floored and steep-sided,
and no more than a metre or so deep
32. Cont’d
• Rainwater collecting in the basins may overflow
to produce spillways, and some basins may
contain incised spillways that lead to their being
permanently drained.
• Rock-basins start from small depressions in
which water collects after rainfall or snowmelt.
• The surrounding surfaces dry out, but the
depression stays moist or even holds a small pool
for long periods, so providing a focus for more
rapid weathering.
• In consequence, the rock-basin expands and
deepens.
• As rock-basins expand, they may coalesce to form
compound forms.
33. Cont’d
• Tafoni (singular tafone) are large weathering features
that take the form of hollows or cavities on a rock
surface.
• The origins of tafoni are complex.
• Salt action is the process commonly invoked in tafoni
formation, but researchers cannot agree whether the
salts promote selective chemical attack or whether they
promote physical weathering, the growing crystals
prising apart grains of rock.
• Both processes may operate, but not all tafoni contain
a significant quantity of salts.
• Once formed, tafoni are protected from rain wash and
may become the foci for salt accumulations and further
salt weathering.
35. Cont’d
• Honeycomb weathering is a term used to
describe numerous small pits or alveoli, no
more than a few centimetres wide and deep,
separated by an intricate network of narrow
walls and resembling a honeycomb.
• They are often thought of as a small scale
version of multiple tafoni.
36. Cont’d
Overall susceptibility to weathering
• sedimentary rocks weather faster than
crystalline rocks (porosity).
• mafic crystalline rocks weather faster than
felsic ones (ionic vs. covalent)
• foliated metamorphic rocks may allow
enhanced weathering parallel to foliation
• limestone (soluble CaCO3) is less resistant
than silicate rocks in humid climate.
38. Slope Stability
• There are two main types of slope instability;
a) surface erosion and
b) landslides.
• Surface erosion is a water-driven process,
occurring largely during and after periods of
intense rainfall.
• landslides are gravity-driven (although they
are often exacerbated by heavy rainfall).
39. Landslide
• Landslides are rock or soil movement on slopes
due to gravity.
• Basically, the factors of landslide can be
categorized into two broad categories:
1) Natural Factors: Gravity, geology, slope, wave
action, heavy and prolonged rainfall, earthquake,
forest fire, and volcano.
2) Anthropogenic Factors:
• Inappropriate drainage system
• Cutting & deep excavations on slopes for
buildings, roads, canals & mining
• Change in slope/land use pattern, deforestation,
agricultural practices on steep slopes
40. Types of Landslides
The landslide classification based on Varnes'
(1978) system has two terms:
a) the material type,
b) the type of movement.
41. Cont’d
Based on Material Type
• Rock: is “a hard or firm mass that was intact and in its
natural place before the initiation of movement”.
• Soil: is “an aggregate of solid particles, generally of
minerals and rocks, that either was transported or was
formed by the weathering of rock in place. Gases or liquids
filling the pores of the soil form part of the soil”.
• Earth: “describes material in which 80% or more of the
particles are smaller than 2mm, the upper limit of sand
sized particles”.
• Mud: “describes material in which 80% or more of the
particles are smaller than 0.06mm, the upper limit of silt
sized particles”.
• Debris: “contains a significant proportion of coarse
material; 20% to 80% of the particles are larger than 2mm,
and the remainder are less than 2mm”.
42. Cont’d
Based on types of movement
• fall,
• topple,
• Slide (translational and rotational)
• spread,
• flow.
Combining the two terms gives classifications
such as: Rock fall, Rock topple, Debris slide,
Debris flow, Earth slide, Earth spread etc.
43.
44.
45. Cont’d
• Understanding and recognizing the differences
in slope form is key in potentially unstable
landform recognition.
• There are three major slope forms to be
observed when looking across the slope
(contour direction):
a) divergent (ridge top),
b) planar (straight), and
c) Convergent (spoon-shaped)
46. Cont’d
• Landslides can occur on any of these slope forms
but divergent slopes tend to be more stable than
convergent slopes because water and debris
spread out on a divergent slope whereas water and
debris concentrate on convergent slopes.
• Convergent slopes tend to lead into the stream
network, encouraging delivery of landslide debris
to the stream system.
• Planar slopes are generally less stable than
divergent slopes but more stable than convergent
slopes.
• In the vertical direction, ridge tops are convex
areas (bulging outward) and tend to be more
stable than planar (straight) mid-slopes and
concave areas (sloping inward)
Mid oceanic ridges is an underwater mountain system formed by plate tectonics. It consista of various mountain inked in chains.
Sea floor spreading z process zat occur in mor where new oceanic crust is formed through volcnic activites & zen gradually moves away from the ridge.