الاشكال الارضية والخرائط pdf - د.علاء حمدون

LANDFORMS AND

GEOMORPHOLOGICAL

MAPPING



Topography

refers to the elevation and relief of the Earth’s surface.



Landforms

are the topographic features on the Earth’s surface.



Geomorphology

is the study of earth surface processes and landforms.

BASIC DEFINITIONS

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The maps above represent the same area on Earth’s surface and they show three different

ways we can view landforms. The image on the far left is a clip from a topographic elevation

map, the image in the middle is an infrared aerial photo, and the image on the right is the

geologic interpretation of surface sediments and geomorphology. This location is interesting

because it contains elements of a natural and human altered physical environment. The lake

in the image, (coded blue in the topographic and geology map, and black in the infrared

aerial photo) was formed by artificial damming a stream the flows through this landscape.

•

Landforms are the individual topographic features exposed on the Earth’s surface.

•

Landforms vary in size and shape and include features such as small creeks or sand dunes, or large

features such as the Mississippi River or Blue Ridge Mountains.

•

Landforms develop over a range of different time-scales. Some landforms develop rather quickly (over a

few seconds, minutes, or hours), such as a landslide, while others may involve many millions of years to

form, such as a mountain range.

•

Landform development can be relatively simple and involve only a few processes, or very complex and

involve a combination of multiple processes and agents.

•

Landforms are dynamic features that are continually affected by a variety of earth-surface processes

including weathering, erosion, and deposition.

•

Earth scientists who study landforms provide decision makers with information to make natural resource,

cultural management, and infrastructure decisions, that affect humans and the environment.

LANDFORMS

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Beaches

Rivers and Flood Plains

Mountains

• Geomorphology is the process-based study of landforms.



Geo-morph-ology

originates from Greek: Geo meaning the “Earth”, morph meaning its

“shape”, and ology refers to “the study of”.



Scientists who study landforms are

Geomorphologists

• Geomorphology defines the processes and conditions that influence landform development,

and the physical, morphological, and structural characteristics of landforms.

• Geomorphologists who study landforms often seek to answer fundamental questions that

help them study landforms, such as:

– What is the physical form or shape of the landform?
– What is the elevation and topographic relief of the landform?
– How did the landform originate?
– What is the distribution of the landform and where else does it occur?
– Are their any patterns associated with the landform or topography?
– What is the significance of the landform in relation to other elements of the landscape

or environment?

– Has the landform or geomorphology been altered by humans?
– Does the landform or geomorphology affect humans?

GEOMORPHOLOGY

Table of Contents

• Constructive processes build landforms through tectonic and depositional

processes.

– Tectonic processes

include movements at plate boundaries, earthquakes,

orogeny, deformation, and volcanic activity.

– Deposition

is the accumulation or accretion of weathered and eroded materials.

• Destructive processes break down landforms through weathering, erosion,

and mass wasting.

– Weathering

is the disintegration of rocks by mechanical, chemical, and biological

agents.

– Erosion

is the removal and transportation of weathered material by water, wind,

ice, or gravity.

– Mass wasting

is the rapid down-slope movement of materials by gravity.

CONSTRUCTIVE AND DESTRUCTIVE

PROCESSES

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Endogenic Process

Exogenic Process

CONSTRUCTIVE PROCESSES



Constructive processes

are responsible for physically building or

constructing certain landforms. Constructive processes include

tectonic

and

depositional processes

and their landforms.



Tectonic Landforms

are created by massive earth movements due to tectonic and

volcanic activity, and include landforms such as:

mountains, rift valleys, volcanoes,

and intrusive igneous landforms



Depositional Landforms

are produced from the deposition of weathered and eroded

surface materials. Depositional landforms include features such as:

beaches, barrier

islands, spits, deltas, flood plains, dunes, alluvial fans, and glacial moraines.

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Floodplain deposits at the confluence

of Mississippi and Arkansas Rivers.

The Stromboli Volcano erupting off the

coast of Sicily in the Mediterranean Sea.

Source: wikimedia commons

DESTRUCTIVE PROCESSES



Destructive

processes

create landforms through

weathering

and

erosion

of surface materials facilitated by water, wind, ice, and

gravity.

Mass-wasting events

occur in areas where weathering and

erosion is accelerated.



Weathering

is the disintegration and decomposition of rock at or near the Earth’s

surface by

mechanical, chemical, or biological

weathering processes.



Erosion

is the removal and transportation of weathered or unweathered materials

water, wind, ice, and gravity



Mass-Wasting

is a rapid period of weathering and erosion that removes and

transports materials very quickly and is often triggered by an environmental stimuli.

Mass wasting includes

rock falls, landslides, debris and mud flows, slumps,

and creep



Landforms formed by destructive processes include

river and stream

valleys, waterfalls, glacial valleys, karst landscapes, coastal cliffs, and

wave-cut scarps.

• The genetic landform classification system groups landforms by the dominant set of

geomorphic processes responsible for their formation. This includes the following
processes and associated landforms:

– Tectonic Landforms
– Volcanic Landforms
– Fluvial Landforms
– Karst Landforms
– Aeolian Landforms
– Coastal Landforms
– Glacial Landforms

• Within each of these genetic classifications, the resulting landforms are a product of

either

constructive

and

destructive processes

or a combination of both.

• Landforms are also influenced by other agents or processes including time, climate,

and human activity.

GENETIC LANDFORM CLASSIFICATION

• Tectonic landforms

• Folding
• Faulting
• Structural ridges
• Fractures

– Domes and Basins
– Horst and Graben Rift Valleys

TECTONIC LANDFORMS

–

Folding occurs when rocks are compressed or deformed and they buckle under

the stress.

–

The diagram below is a cartoon illustrating how rocks fold.

FOLDING



The crest of the fold, where the

rock layers slope downward

form the

anticline.



The valley of the fold where the

layers slope toward the lower

axis form the

syncline.

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–

Anticlines and synclines can take on slightly different geometries depending on the compressional forces that

form them.

–

Very intense compressional forces form tight isoclinal folds, less intense compressional forces produce open

folds.

–

Folds can be asymmetric, upright, overturned, or curved. A fold pushed all the way over onto its side is called

recumbent.

–

Twisting or tilting during rock deformation and compression can cause folds to form at different angles.

–

Some folds are very small and can be viewed in hand held specimens, while other folds are as large as a

mountain and can be viewed from aerial photos.

FOLDING

Anticline exposed along NJ Route 23 near

Butler NJ. The man in the bottom of the

photo helps show the scale of the folds.

Syncline valley between

mountain peaks.

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• Meza             0-5
• Cuesta              5-15
• Hogback           15-35
• Dike-like ridge   <35

STRUCTURAL RIDGES

MEZA

CUESTA

HOGBACK

DIKE-LIKE

RIDGE

– Faulting occurs when the rocks fail under deformation processes. A fault is a planar discontinuity along

which displacement of the rocks occurs.

– There are four basic types of faulting: normal, reverse, strike-slip, and oblique

– Geologists recognize faults by looking for off-set rock layers in outcrops.
– Faults may also be recognized by debris, breccia, clay, or rock fragments that break apart or are

pulverized during the movement of the rocks along the fault plane. Fault ‘gouge’ is a term used to
describe the material produced by faulting.

– If a fault plane is exposed, there may be grooves, striations (scratches), and slickenslides (symmetrical

fractures) that show evidence of the rocks movement.

– Large fault systems, such as the San Andreas fault can be seen from aerial imagery.

FAULTING

1. Normal

: rocks above the fault plane, or hanging

wall, move down relative to the rocks below the

fault plane, or footwall.

2. Reverse

: rocks above the hanging wall moves up

relative to the footwall

3. Strike-slip

: rocks on either side of a nearly

vertical fault plane move horizontally

4. Oblique-slip

: normal or reverse faults have some

strike-slip movement, or when strike-slip faults

have normal or reverse movement

Normal

Reverse

Strike-Slip

FAULTING

– Joints occur where a rock breaks but there is no displacement or faulting associated with the break. Joints

are not singular features, but they occur in sets within a given type or area of a rock.

– Fractures are breaks in rocks that are often singular more random features and are not associated with a

set of joints. Fractures often occur in association with faults or folds.

– Crustal movements, deformation, or other tectonic related movements can cause rocks to joint or fracture.
– Joints and fractures form from compression, tension, or shear stress and can range in size from millimeters

to kilometers.

– Common forms of jointing are columnar, sheet jointing, and tensional joints.

• Columnar jointing

occurs when igneous rocks cool and develop shrinkage joints along pillar-like

columns.

• Sheeting joints

occur when the layers of rock release pressure and exfoliate along parallel planes.

• Brittle fractures and tensional joints

are caused by regionally extensive compressional or elongated

pressures along folds in the crustal rocks.

– Sometimes, jointing is obvious, but the processes that caused it may be unknown, or difficult to identify.
– Fractures and joints create a variety of pathways for water to flow through, which weaken the rock and

facilitate chemical, biological, and mechanical weathering processes.

FRACTURES AND JOINTS

JOINTING

These two images are an example of columnar

jointing. The image on the top is a side view and

the image below is from the top. These

hexagonal columns of rock formed from cooled

basalt are part of Devil’s Postpile National

Monument in California.

The image below is of vertical jointed, bedded

meta-sandstone in the Snake Range in Nevada.

• Domes and basins are large, elongated folds formed by broad warping processes including

mantle convection, isostatic adjustment, or swelling from a hot spot.

• Upwarping produces domes, while downwarping produces basins.
• Geologists identify dome and basin structures by the stratified ages of the rock folds:

– Domes

contain strata which increase in age toward the center as the younger layers are

eroded from the top and sides.

– Basins

contain strata which is youngest toward the center and the oldest rocks form

the flanks or sides.

DOMES AND BASINS

This geologic map of the Michigan Basin

illustrates the circular pattern of the

sedimentary strata. The green color in the

center of the map represents the youngest

rocks which are Upper Pennsylvanian; and

the rocks progressively increase in age

toward the periphery where the reddish-

orange colors represent the oldest rocks

flanking this structure which are

Ordovician and Cambrian age.

Youngest rocks (Upper Pennsylvanian)

Oldest Rocks (Ordivician and Cambrian)

• Horst and graben topography is generated by normal faulting associated with crustal extension.
• The central block termed graben is bounded by normal faults and the graben drops as the crust

separates.

• The graben forms an elongated valley that is bound by uplifted ridge-like mountainous

structures referred to as horsts.

• Some horsts may tilt slightly producing asymmetric, tilted terrane or mountain ranges.
• In the Western United States, horst and graben fault sequences are described as “Basin and

Range” topography.

HORST AND GRABEN:

BASIN AND RANGE

Basin and Range topography, Nevada.

• Antarctica: Antarctic Peninsula, Transantarctic Mountains
• Africa: Atlas, Eastern African Highlands, Ethiopian Highlands
• Asian: Himalayas, Taurus, Elburz, Japanese Mountains
• Australia: MacDonnell Mountains
• Europe: Pyrenees, Alps, Carpathians, Apennines, Urals, Balkan Mountains
• North American: Appalachians, Sierra Nevada, Rocky Mountains, Laurentides
• South American: Andes, Brazilian Highlands

MAJOR MOUNTAIN RANGES OF

THE WORLD

Rocky

Mountains

Andes

Mountain

Appalachian

Mountains

Himalaya

Mountains

European Alps

•

The Rocky Mountains, which extend from British Columbia to Texas were formed by the Laramide Orogeny
40-80 million years ago; however, there is still active uplift today.

•

Colorado’s Front Range, the Sangre de Cristo Mountains of Colorado and New Mexico, the Franklin Mountains
in Texas, and Wyoming’s Bighorn Mountains are all part of the “Rocky Mountain Range”.

ROCKY MOUNTAINS

The Laramide Orogeny was characterized by intense

tectonic activity resulting from a series of compressional

and extensional events. The subduction of the Pacific

Ocean Plate caused compressional forces in the continental

plate, and pushed the oceanic plate downward. Following

subduction of the oceanic plate, upwelling and extensional

forces caused the literal uplift of the continental bedrock

and formed of the Rocky Mountains. The lower crust in this

region of upwelling and uplifting is relatively thin and

stretches under pressure. The upper crust is very brittle and

deforms easily. As a result the upper crust is characterized

by large angular tilted faults blocks which form the Rocky

Mountains we see today.

Source: USGS

The Rocky Mountains contain some of the most

beautiful scenery in North America and are home

to hundreds of parks and recreational areas

including Rocky Mountain National Park,

Yosemite National Park, Glacier National Park,

and Grand Tetons National Park.

• Cinder Cones
• Shield Volcanoes
• Strato (Composite)Volcanoes
• Lava Domes
• Caldera
• Volcanic Necks
• Volcanic Hot-Spots

VOLCANIC LANDFORMS

CINDER CONES

Cinder cones have an easily

recognizable hill shape form with

relatively steep 30-40 degree

slopes. This angle represents the

steepest angle maintained by

unconsolidated, loose material and

is commonly referred to as the

angle of repose. This image is of

an older cinder cone with small

caldera depression on the summit.

CALDERA

Crater Lake in Oregon is

the collapsed caldera of

Mount Mazama and is now

filled in with water.

Wizard Island is a volcanic

cone in the middle of the

lake. Crater Lake is the

deepest lake in the United

States at 1,932 feet deep!

VOLCANIC HOT SPOTS

Kauai

Oahu

Maui

Hawaii

Kahoolawe

Lanai

Molokai

Nihau

Oldest Islands

Youngest Islands

• River Systems and Fluvial Landforms
• Longitudinal Profile and Watersheds
• South Carolina Rivers
• Lakes and Dams
• Mountain Streams
• Straight Rivers
• Braided Rivers
• Meandering Rivers
• Anabranching Rivers
• Gulleys
• River Terraces
• River Canyons
• Waterfalls
• Flood plains
• Alluvial Fans

FLUVIAL LANDFORMS

•

Rivers are one of the most dominant agents of landscape change because their flowing waters are continually
eroding, transporting, and depositing sediments.

•

Rivers are critically important to people because they provide fresh drinking water, transportation of people,
goods, and wastes, hydro-electric power generation, irrigation, and recreation.

•

Rivers, although very important to people, are also very dangerous because flooding is among one of the most
frequent and widespread natural hazards that can damage or destroy land, property, and life.

•

Because rivers systems are so important to humans, it is necessary for scientists to understand how rivers
affect the landscape and also how humans affects rivers. Having this information enables people to better
manage for future water resource needs and prevent hazardous situations.

RIVER SYSTEMS AND FLUVIAL

PROCESSES

•

The

longitudinal profile

of a river is an elevation cross-section of the entire watershed from the source of

flowing water to the mouth of the stream.

– The source area of flowing water is defined as the

headwaters

. Headwaters are the highest elevation

where water collects to form a stream network and is generally formed by either snow-melt runoff, a
natural spring, or rainwater.

– The mouth of the stream is typically defined by the stream’s ultimate

base level

, and this generally

corresponds with the sea level where the river meets the ocean. Base level is the lowest elevation that a
stream can erode its channel. Local or temporary base levels may be formed by reservoirs or waterfalls.

– A river’s gradient (slope) is steepest near the headwaters and gentlest near the mouth.

– As rivers flow from their headwaters to their base level they carve valleys into the landscape by

eroding, transporting, and depositing weathered rocks, soil, and sediment.

•

watershed

basin

is the area of land bound by a local elevation ridge, referred to as a

drainage divide

where all the water within that area drains downstream from its headwaters to a single outflow location. A
watershed can include an entire river system from it headwaters to ultimate base level, or smaller watersheds
can encompass tributary sub-basins that are part of the larger watershed.

•

Drainage divides are high elevation ridges that separate one watershed from another.

LONGITUDINAL PROFILE AND

WATERSHEDS

LONGITUDINAL PROFILE AND

WATERSHEDS

Longitudinal River Profile

tio

3,000

Headwaters

Ultimate

Base level

River Length (Miles)

100

This diagram outlines the longitudinal profile of a

river basin from the headwaters to the ultimate

base level, or sea level. A rivers gradient is

steepest near the headwaters and gentlest near

the base level. In South Carolina, the steepest

sections are often found in the blue Ridge and

Piedmont, while the gentler gradient occurs in the

Coastal Plain. River length, or distance, is

measured from the rivers mouth to its headwaters,

seemingly reversed from what one might expect.

Headwaters:

multiple low-order

streams near

drainage divide

Base level:

single outflow and

highest order

stream

This figure is a hypothetical river basin. The black

dotted line represents the drainage divide and the

numbers refer to stream order. Any rainfall that falls

within the black dotted line will eventually flow into the

main stem river and out at the mouth. Stream order

increases from the headwaters to the base level. In this

example, the river is a5

-order river.

Stream Order:

order and 1

order = 2

order

order and 2

order = 3

order

order and 3

order = 4

order

order and 4

order = 5

order

And so on, 5 and 5 =6, 6 and 6 =7

order…

RIVERS AND BASINS

BRAIDED

• Braided river patterns occur in high-energy environments that contain an excessive sediment

load that is deposited on the bed of the channel. The stream loses the capacity to transport the
sediments and it forces its way through the accumulation of sediments forming an interwoven
network of channels.

• The islands between the braided channels are ephemeral and dynamic. The sediment is

continually remobilized, transported and deposited, leaving minimal time for vegetation to
establish, as a result they are rarely vegetated.

• Braided channels tend to be wide and shallow with defined banks that are higher than the mid-

channel islands.

• Braided channels occur downstream of areas with high sediment loads. Their sediment textures

vary from silts, sands, and gravels depending on the sediment source.

MEANDERING

• Meandering river patterns are low-gradient, sinuous channels that contain multiple, individual

meander bends that are laterally migrating across the flood plain.

• As they migrate or move across the flood plain they are continuously eroding, transporting, and

depositing alluvial sediments.

• Meandering rivers and their hydrologic conditions create a variety of depositional and erosional

landform features that collectively form the flood plain valley.

• The primary features of meandering channels are the aggrading pointbar deposit on the inside

of a meander bend and eroding cut bank along the outside of the bend. As the channel
migrates laterally across the flood plain, sediments are eroded from the outer cutbank and
deposited on the inner pointbar.

• Occasionally, meandering channels cut-off entire meander bends; these cut-offs are

incorporated into the flood plain as oxbow lakes or in-filled channels.

2006 Aerial imagery: http://www.dnr.sc.gov/GIS/gisdata.html

Cliffs or escarpment

• Flood plains are the landform adjacent to the

river channel that is influenced by modern river
processes. Flood plains are constructive,
depositional landforms created by stream flow
and sediment deposition.

• Flood plain environments are composed of a

mosaic of different landform features including

cutbanks

pointbars

natural levees

crevasse

channels

and

crevasse splays

infilled channels

and

oxbow lakes

backswamps

, and

occasionally yazoo tributaries and other flood
plain channels.

FLOOD PLAINS

Pointbar

Cutbank

Oxbow

Lakes

Infilled

Channel

• River terraces are older remnant flood plain surfaces that are higher in elevation than the

modern flood plain. They may occur on one or both sides of the valley.

• Terraces are formed when the river channel cuts down into the flood plain and laterally erodes

the alluvial valley, carving a new river channel and flood plain entrenched within the older flood
plain surfaces. Down cutting can occur because of hydrologic or sedimentary changes in the
headwaters or valley gradient changes caused by a retreating sea-level and lowered or extended
base-level. Terraces can also form from tectonics and valley uplifting.

• Terraces are generally isolated from the more recent river processes and may only flood during

100 or 500 year flood events. River terraces are often archeological hot spots because they
contain artifacts from historic colonies that used the river and flood plain.

RIVER TERRACES

Terrace 1

Terrace 2

Terrace 3

River Channel and Modern Flood Plain

Terrace 4

•

Waterfalls occur where there is resistant bedrock, abrupt changes in bedrock resistance, or along fractures
or faults in the bedrock.

•

Less resistant materials are weathered more quickly than resistant rocks, creating stair-stepped ledges or
drop offs where waterfalls occur. Less resistant rocks may also form pools between resistant rocks that
form waterfalls.

•

Faults and fractures often provide natural pathways for the downslope movement of water.

•

The location of the waterfalls origin may be referred to as a “knick-point”, continued weathering by the
stream flow causes the knick-point to slowly migrate upstream.

•

Most waterfalls in South Carolina occur along streams in the Blue Ridge, Piedmont, and the along the
Regional Fall Line where there are rock layers of varying resistance.

WATERFALLS

This waterfall was formed by differential

weathering between the softer shale and

harder more resistant limestone.

Lower White Water

Falls in the Jocassee

Gorges area of South

Carolina drops nearly

200 ft. Here, the

Toxaway Gneiss forms

a resistant bedrock

that the Lower White

Water River flows over

before draining into

Lake Jocasse.

• Alluvial fans are fan-shaped fluvial deposits that accumulate at the base of stream

where it flows out from a steep gradient and enters into a lower-gradient flood
plain or valley setting.

• The stream enters the valley carrying a higher capacity sediment load than it can

continue to carry, and as a result it deposits the sediments as an alluvial fan.

• Alluvial fans generally form in arid environments with a high sediment load and

where there is minimal vegetation to disrupt the fan formation.

• Alluvial fans may form from a single high-flow event or from the accumulation of

multiple events.

ALLUVIAL FANS

This alluvial fan is carrying a high sediment

load from material weathered from the

mountains. The dark line along the edge of the

fan is a road. Because the road is not buried by

recent deposits it suggest that this fan is not

currently as active as it was in the past.

GULLYS

– Gullys are formed by hillslope erosion.
– Rainwater runoff draining over the surface of a hillslope generates erosive

overland flows that remove weathered rocks and soil.

– When multiple gullys form they produce a disconnected network of headwater

channels that dissect the hillslope and increase soil erosion.

– Gullys primarily form on disturbed hillslopes where forest and vegetation have

been cleared.

The forest was cleared from this hill

slope and corn was planted on the bare

soil. Following the first few rain events,

gullys began to form as a result of soil

erosion. The gullys only carry water

during rainfall events.

• Caverns
• Sinkholes
• Disappearing Streams
• Springs
• Towers

KARST LANDFORMS

Karst is a term used to describe landscapes that are formed by chemical weathering

process controlled by groundwater activity. Karst landscapes are predominantly

composed of limestone rock that contains > 70 percent calcium carbonate.

SINKHOLES

•

Dunes

•

Loess Formations

•

Carolina Bays

AEOLIAN LANDFORMS

Aeolian landforms are formed by the deposition of windblown sediments. The sediments

are generally sourced from deserts, glacial deposits, rivers, or coastal shorelines. Aeolian

sediments are often composed of well-rounded, sand-to silt-sized particles, that are

weathered by wind abrasion during transport. Sediments are deposited when the

velocity of the wind falls and there is not enough energy available to entrain and

transport the sediments. Sands will begin to accumulate wherever they are deposited

and often continue to move along the ground.

•

Barchan dunes

are solitary, crescent shaped dunes with their tips pointing downwind. They form where sand

source is limited, wind direction is constant, and the ground is void of vegetation. They can reach heights of
30 meters and spread nearly 300 meters.

•

Transverse dunes

are a series of long ridges that are parallel to one another, and are perpendicular to the

prevailing wind. They form in areas where the prevailing winds are steady, there is an abundant supply of
sand, and vegetation is sparse. They can reach heights of 200 meters and may extend for 100’s of kilometers.

DUNES

Barchan Dunes

Wind

Transverse Dunes

Wind

Wind direction

slip face

Sand avalanche

Dune movement

• Littoral Zone
• Beaches
• Barrier Islands
• Beach Ridges
• Spits
• Deltas
• Coastal Cliffs
• Marine Terraces
• Wave-Cut Scarps

COASTAL LANDFORMS

Hawaiian coastline

Coastal landforms include a diverse array of shoreline and near-shoreline

features, as well as some coastal plain landforms far removed from the modern

ocean by long term sea-level changes. This section will explore both constructive

and destructive landforms formed by current coastal processes, as well as

marine related landforms that were formed during periods of higher sea level.

Littoral Zone

DELTAS



Deltas form where the mouth of a river meets its ultimate base level at the ocean or

sea. As the river’s velocity decreases, it looses the capacity to carry its sediment load

and the resulting deposits form a delta. Delta shapes and forms vary depending on

tidal influences, waves, currents, sediment type and quantity, river discharge, and the

stream gradient near the outlet. The most common types of deltas include bird-foot,

estuarine, and arcuate.



Not all rivers form deltas, for example the Amazon deposits its sediment load directly

into the ocean onto an underwater seaward sloping continental shelf. The Columbia

River in the northwest United States, lacks a delta altogether, because the currents

are too strong and erosive for the sediments to deposit.

Mississippi River Delta: Bird-Foot Delta

DELTAS

Nile River and Arcuate Delta

ACE Basin: Estuarine Delta

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•

Sea cliffs are erosional landforms formed by the undercutting action of the sea against the

coastline.

•

The eroded sea cliff becomes notched inland where the waves erode the coastline and

eventually the overhanging land collapses into the ocean. This process causes the sea cliff to

slowly retreat inland eroding more and more of the coastline.

•

In undeveloped areas sea cliff related erosion does not pose a hazard. Unfortunately

extensive areas of the California and Oregon coast are developed near sea cliffs that are

threatened by the erosive force of the Pacific Ocean.

SEA CLIFFS

Headlands

Sea cliff

MARINE TERRACES



Marine terraces are wave-cut platforms that form a series of terraces that

progressively increase in elevation and age away from the modern coastline.



Marine terraces usually form as a result of either sea-level changes, tectonic uplifting,

or a combination of both processes.



Marine terrace are composed of shallow to deep marine deposits and often contain

fossil remains which provide a method for relative age dating.



Scarps form the boundaries between successive marine terraces and often mark

some indicator of landscapes response to environmental changes.

•

Ice sheets and Alpine Glaciers

•

Ice Field and Ice Caps

•

Piedmont Glacier

•

Tidal Glaciers and Icebergs

•

Glacial U-shaped Valleys

•

Fjords

•

Hanging Valleys

•

Cirques and Cirque Glaciers

•

Arêtes, Horns, Cols

•

Lateral and Medial Moraines

•

End and Terminal Moraines

•

Paternoster Lakes

•

Kettles

•

Erratics

•

Drumlins

•

Outwash Plain

GLACIAL LANDFORMS

Glaciers are large masses of moving ice. Because glaciers

are “frozen” they are part of the Earth’s cryosphere,

which accounts for 77 percent of all Earth’s freshwater.

Glaciers are very sensitive to the slightest temperature

changes. Over Earth’s geologic history the spatial extent

and size of glaciers has expanded and shrunk numerous

times. As a result, glacial landforms can be found in

locations that currently have no active glaciers or

glaciation processes. Presently, glacial landforms occur in

two distinct geographic regions, high latitude polar

environments and high altitude mountain environments.

In this section we will explore glacial landforms from their

present context and from a historic look into the past.

Alpine Valley Glacier in Alaska.

• Cirques are bowl-shaped eroded, depressions near-mountain top ridges where snow

accumulates and forms the head of an alpine glacier.

• Glaciers in this early phase of formation are often referred to as cirque glaciers. The

confluence of multiple cirque glaciers merges to form a valley glaciers. Cirque glaciers

feed valley glaciers a relatively steady source of new snow.

• When glaciers retreat, the cirque is often the last part of the glacier to melt.

CIRQUES AND CIRQUE GLACIERS

Cirque Glaciers

LATERAL AND MEDIAL MORAINES

GEOMORPHOLOGICAL

MAPPING