Summary of the Chapter
All landforms are composed of rocks or
their weathered by products. Three main types of rocks
can be identified on the Earth's surface: igneous,
sedimentary and metamorphic. The rock cycle is a model
that describes how various geological processes create,
modify and influence rocks. The rock cycle suggests
that all rocks originated from magma. This model also
suggests that all rock types can be melted back into
magma by tectonic forces that return rock to the mantle.
Time has a unique meaning
to geoscientists. To a geoscientist time is not measured
in seconds, minutes or days, but in eons, eras, periods,
and epochs. Each one of these units measures time according
to major geologic events that have occurred over the
4.6 billion years of Earth history. When a geoscientist
mentions the Cretaceous we know that this is a time
period that occurred between 65 to 144 million years
Uniformitarianism is an important theory
central to understanding in geology and geomorphology.
This theory suggests that the continuing uniformity
of existing geomorphic and geologic processes should
be used as the intellectual framework for understanding
the geologic history of the Earth. It rejects the idea
that the landscape of the Earth is the result of catastrophic
processes (e.g., the biblical flood).
Three types of rocks are recognized by
geologists: igneous, sedimentary, and metamorphic.
Igneous rocks are formed by the solidification of magma.
This solidification can occur at or beneath the Earth's
surface. Sedimentary rocks develop from the lithification
of sediments or weather rock debris. Two general categories
of sedimentary rocks exist: clastic and non-clastic.
Metamorphic rocks are created by the alteration of
existing rocks by intense heat or pressure.
Most rocks are composed
of one or more minerals. The minerals that make up
a rock can be produced by magma solidification (igneous
rocks), sedimentation of weather rock debris (sedimentary
rocks), or metamorphism (metamorphic rocks). Minerals
are naturally occurring inorganic solids that have
a crystalline and a unique chemical make-up. Geologists
have discovered more than 2000 different types of minerals.
The various types of minerals have been classified
into nine groups.
Igneous rocks are produced by the crystallization
of magma. This process can occur at the Earth's surface
or beneath the ground. The type of igneous rocks that
forms from solidification is controlled primarily by
magma chemistry, temperature of crystallization, and
rate of cooling. Four basic types of magma have been
classified by geologists. This classification is based
Felsic magma contains relatively high
quantities of sodium, aluminum, potassium, and silica.
Its solidification produces granite, dacite, rhyolite,
and granodiorite. Each of these rocks has a unique
mineral composition and grain size.
Mafic magma is rich in calcium, iron,
magnesium, and relatively poor in silica (between 45
to 52%). The rocks that are created from this magma
include basalt and gabbro. These rocks are dominated
by the minerals pyroxene, amphibole, and olivine.
Intermediate magma produces andesite
and diorite. These rocks contain less silica (between
53 to 65%) and have a chemistry that is between felsic
and mafic. Dominant minerals in these rocks include
pyroxene, amphibole, and plagioclase feldspars.
rocks contain relative low amounts of silica (< 45
%) and are dominated by the minerals olivine, calcium-rich
plagioclase feldspars, and pyroxene. Peridotite is
the most common ultramafic rock.
The Bowen reaction series is a model
that suggests that the type of igneous rocks that form
from felsic and mafic magma relies on the temperature
of crystallization and the chemical composition of
the originating magma. In this model, the formation
of minerals starts with two different chemical sequences
at high temperatures that eventually merge into a single
series at cooler temperatures.
Three different types of sedimentary
rocks exist. Most sedimentary rocks are of the clastic
type. These rocks are formed by the lithification of
weathered rock debris. Examples of clastic sedimentary
rocks include sandstone, shale, and conglomerate. Identification
of clastic sedimentary rocks is based on sediment particle
The other two types of sedimentary rocks
are termed non-clastic. The first group of non-clastic
sedimentary rocks form through the chemical precipitation
and re-crystallization of elements and compounds in
solution. Common precipitated sedimentary rocks include
halite, gypsum, silcretes, ferricretes, limestone,
and dolomite. The second group of non-clastic sedimentary
rocks are created from the lithification of once living
organisms. Some examples of these rocks are limestone,
chalk, coal, and lignite.
Metamorphic rocks are created by the
alteration of existing igneous or sedimentary rocks
by heat, pressure, or through the chemical action of
fluids. This alteration may cause simple chemical changes
or structural modifications to the minerals found in
the rock. Some common metamorphic rocks include slate,
schist, gneiss, marble, and quartzite.
Heat begins to metamorphically
change at a temperature of about 200 degrees Celsius.
Heat can be applied to rocks through two processes:
tectonic subduction and the intrusion of magma. Another
name for this process is called thermal metamorphism.
Pressure alters rocks primarily
by reorienting mineral crystals. Pressure usually acts
in concert with heat. Pressure can be exerted on rocks
through two processes: weight of overlying materials
or through a variety of tectonic processes. Another
name for this process is called dynamic metamorphism.
The alteration of rocks
via the chemical action of fluids requires the presence
of water and carbon dioxide. When water and carbon
dioxide are mixed the fluid that is produced can alter
rocks chemically by dissolving ions and causing chemical
reactions. Another name for this process is called
Internally the Earth is made up of several
different layers. Above the outer core is the mantle.
A number of different layers have been discovered in
the mantle. On top of the mantle is the lithosphere.
The surface of this layer is called the crust.
Through deep drilling and seismic evidence
scientists have learned about the structure of the
Earth. Structurally, the Earth is composed of a number
of different layers. The outer most layer is called
the crust and it sits on top of the mantle. The crust
is a cool, rigid, and brittle layer. Two types of crust
are classified: oceanic and continental. At the center
of the Earth is the core, which is approximately 7000
kilometers in diameter. One interesting property of
the crust is that it has the ability to float up and
down. This process is called isostacy.
The core consists of two sub-layers:
the solid inner core and the liquid outer core. These
two layers are made of the same materials but exhibit
slightly different physical properties. The inner core
composed of nickel and iron and approximately 1220
kilometers in diameter. Surrounding the solid inner
core is the outer core which is liquid in nature. This
layer has a thickness of about 2250 kilometers.
Sitting on top of the core is the mantle.
It is also composed of several different sub-layers.
The upper mantle exists from the base of the crust
downward to a depth of about 670 kilometers. It is
thought to be composed of peridotite. Below the upper
mantle is the lower mantle that extends from 670 to
2900 kilometers below the Earth's surface. This layer
is hot and plastic. The top 100 to 200 kilometers of
the upper mantle is called the asthenosphere.
One other layer often described by geologists
is the lithosphere. The lithosphere consists of the
crust and upper portion of the asthenosphere. This
layer glides over the rest of the upper mantle.
The theory of plate tectonics is another
important unifying idea in geology. Essentially, the
theory suggests that the Earth's outer crust is composed
of a number of plates that float on the mantle. This
idea has been around for more than a century. However,
scientists before 1960 could not explain the mechanism
that moved the Earth's plates. This all changed when
scientists discovered alternating patterns of rock
magnetism in sea floor rocks. The patterns also correlated
to an increasing age of the sea floor as a one moved
away from mid-oceanic ridges. This discovery indicated
that new oceanic crust was created at the mid-oceanic
ridges. It was also discovered that oceanic crust was
destroyed at the oceanic trenches. Many of these trenches
are found in the Pacific Ocean basin bordering continental
crust. Scientists have theorized that convection currents
in the Earth's mantle cause the movement of the plates.
This lecture concludes by showing how plate tectonics
explains earthquakes, mountain building, volcanoes,
and oceanic trenches.
Scientists have discovered that the Earth's
crust consists of two basic types. Continental crust
makes up the continents. Continental crust is mainly
composed of granite, some metamorphic rocks, and sedimentary
rocks. The age of these rocks varies from between 4
billion to 600 million years. The continental crust
varies in thickness from between 10 to 70 kilometers.
It is thickest under mountain ranges. The continents
are actually quite complex geologic structures. At
the center, exists a core of very old igneous and metamorphic
rock that is called the basement of rock. Along and
the margin of the basement rock are deposits of sedimentary
rock that are called platforms. Together the basement
rock and the platforms form a craton. Along the edges
of the cratons are the continental margins and mountain
belts. Rock mass is also added to the continents through
a variety of intrusive and extrusive igneous processes.
Oceanic crust is created at the mid-oceanic
ridges and destroyed at the oceanic trenches. Oceanic
crust is relatively young age and is being created
even today at mid-oceanic rift zones. Maximum age is
about 200 million years. On average of oceanic crust
is 7 km thick and mainly composed of the igneous rock
Mountains can be created by two processes
on our planet. Some mountains owe their origin to vertical
movements of rising magma at hot spots and along the
margin of subduction zones. These processes produce
isolated volcanic mountains. Many mountains occur as
a linear group. The mechanism responsible for mountain
ranges is tectonic plate collision. Colliding plates
push sedimentary materials into an uplifted mass of
rock that contains numerous folds and faults. The Earth
has undergone a number of mountain building periods.
For example, the Himalayas began the formation of about
45 million years ago. This orogeny is still going on
Geologists have developed a general model
explain how most mountain ranges form. This model suggests
that now and building involves three stages. The first
stage involves the accumulation of sediments. In the
second stage, tectonic collision causes rock deformation
and crustal uplift. In the final stage, isostatic rebound
continues to cause uplift despite erosion and causes
the development of new mountain peaks through block
The Earth's crust shows evidence that
large-scale tensional and compressional forces have
deformed it. This deformation has created a variety
of different folds and faults. A fold can be defined
as a bend in rock that is due to compressional forces.
Folds occur when the stress applied to rock does not
exceed its internal strength and plastic deformation
occurs. These bends are most obvious in sedimentary
rocks that have beds of strata that were originally
laid down horizontally. The simplest types of folds
include monoclines, anticlines, and synclines. A recumbent
fold is a more complex type of fold where one limb
of the fold passes the vertical. Faults form when the
stress applied to rock does exceed its internal strength.
This condition causes the rock to rupture along a fault
plane (area of weakness and fracture). A number of
fault types are defined including normal, reverse,
graben, horst, and strike-slip.
An earthquake is a sudden vibration of
some portion of the lithosphere. It is caused by the
quick release of potential energy through motion. Most
earthquakes are the result of rock moving because of
faults, tectonic subduction, or rifting. The Earth
experiences about 150,000 significant tremors a year.
But most of these events are just strong enough to
be felt, only a few a cause large-scale damage. Earthquakes
energy is transmitted to surround rock by seismic waves.
Geologists have discovered that seismic motions actual
consist of three different types waves: P-waves; S-waves,
and surface waves. P-waves (by expansion and contraction
of rock as the wave moves away from the focus) and
S-waves (movement of rock perpendicular to the direction
of seismic wave travel) travel through the body of
rock. Surface waves produce a rolling or swaying motion
on the surface of the effected rock.
The strength of earthquakes is usually
measured relative to the Richter scale. This scale
is logarithmic so each increase in magnitude represents
10 times more energy released by the quake.
Earthquakes cause considerable damage
to the built environments of humans. However, the level
of damage caused by an earthquake is not always related
to its magnitude. The level of damage can be influence
by time of occurrence, duration of the event, geology
of the effected area, type of building construction,
and population density. Earthquakes can also trigger
several other damaging phenomena. This includes mass
movements, fires, and tsunamis.
Volcanoes are openings on the Earth that
release lava, tephra, and volcanic ash. Most of the
Earth's volcanoes are located at or near tectonic subduction
zones and the mid-ocean ridges. Some volcanoes are
the result of lithospheric hots spots. Geologists have
classified volcanoes into five different types. This
classification is based on geomorphic form, magma chemistry,
and the explosiveness of the eruption. The various
types include: basalt plateau volcanoes, shield volcanoes,
cinder cones, composite volcanoes, and explosive calderas.
The Earth's terrestrial surface or continents
are made up of three types of landscapes: cratons;
mountain belts, and the continental margins. All of
the continents have the same construction. In their
center is a nucleus very old rock basement rock that
is made up of a mixture of igneous and metamorphic
rocks. The exposed top of this feature is called shield.
Large areas of basement rock are covered by relative
flat sedimentary strata called the platform. Together
the platform and basement rock form a craton. Some
continental masses have several cratons that are separated
from each other by mountain belts. Most of the continental
mountain belts are found along the edge of the cratons.
Mountain belts are formed when tectonic forces squish
marine sedimentary deposits to the edges of the continents.
This squishing process causes the sedimentary layers
to become folded and faulted and their elevation increases
to form mountains. Between the mountain belts and the
ocean basins is the continental margin. Much of this
continental surface is located below sea-level. The
continental margin is made up three distinct landform
types: the continental shelf; the continental slope;
and the continental rise.
The other major topographic feature of
the Earth is the ocean basins. The ocean basins are
made up of relatively young basaltic volcanic rock
that was released from fissures along the mid-ocean
ridge. Oceanic crust is returned to the mantle at the
subduction zones found along the continental margins.
The ocean basins are not featureless. Some of features
found here include the ocean floor, mid-oceanic ridges,
ocean trenches, and numerous volcanoes (many of which
Geologists and geomorphologists recognize four basic
types of landforms: structural landforms; weathering
landforms; erosional landforms; and depositional landforms.
Landforms and the geomorphic processes that create
them are uniquely interrelated. Not only do the actions
of geomorphological processes shape the landscape,
landscape also determines which processes occur and
at what rates they occur.
Weathering is the breakdown and alteration
of rocks and minerals at or near the Earth's surface.
The end products of weathering are the breakdown of
a single mass into two or more smaller masses, the
removal of atoms or molecules from the weathered surface,
and the addition of certain atoms and molecules to
the weathered surface. The products of weathering are
a major source of sediments for the geomorphic processes
of erosion and deposition. Rock and mineral weathering
can be the result of a number of physical, chemical
and biological processes. Physical weathering involves
the disintegration of material by mechanical stress
and rupture. Processes that can result in physical
weathering include abrasion, crystallization, thermal
insolation, wetting and drying and pressure release.
Chemical weathering results from the chemical alteration
of rock and minerals. The most common chemical weathering
processes are hydrolysis, oxidation, reduction, hydration,
carbonation, and solution. Finally, biological weathering
involves the breakdown or rock and minerals through
chemical and/or physical agents of an organism. A number
of processes involved in biological weathering are
The effects of weathering on the nature
of the landscape are evident in almost all landforms.
On the surface of many landforms we can find layers
of soil and regolith. Soil and regolith represent the
accumulation of small particles of rocks and minerals
that were derived from disintegration of much large
pieces of bedrock. The region of the earth with the
most active soil formation is the tropics because of
high temperatures and an abundance of moisture. In
regions of limestone bedrock, the effects of chemical
solution can produce a number of unique geomorphic
features that are the result of the dissolving and
deposition of calcium carbonate. High latitude regions
of the world also have landform features that are the
result of weathering. Freeze-thaw action and frost-shattering
along with the action of some other geomorphic processes
cause the formation of a number of types of patterned
In the previous lectures we learned that
one of the by-products of rock weathering was the development
of soils. However, soils are much more than just an
assortment of fine mineral particles. A true soil is
composed of 4 things: mineral particles, air, water,
and organic material. A true soil is also the product
of the activities of living organisms. There are also
a number of features found in a true soil that distinguish
it from simple mineral sediments. True soils are influence,
modified, and supplemented by living organisms. Living
organisms are the source of the organic matter found
in soils. They also are responsible for decomposing
organic matter into humus and then finally back into
inorganic elements and compounds.
Soils often show the effects of translocation
of clay and dissolved substances because of the downward
movement of water through the soil profile. The process
of removal of these materials from a horizon within
the soil is called eluviation. The deposition of these
material in a deeper layer is called illuviation. The
complete removal of chemical substances from a soil
is known as leaching.
The particles that make up a soil can
be three size types: clay; silt; and sand. Some soils
are composed of just one particle type. A loam is a
soil that has equal quantity of clay, silt, and sand.
Of these particles clay is probably the most important.
Because of its large surface area, clay has the ability
to hold onto large quantities of nutrients.
A variety of inorganic and organic chemical
reactions occur within a soil horizon. One effect of
these reactions is that soils can become acidic or
alkaline in pH. Soil pH also influences the fertility
of a soil. The most fertile soils have a pH that is
Soil can vary in their color. Color can
be used as a indicator of processes acting on a soil
or the acumulation of organic matter and other substances.
The last distictive characteristics of
a soil is the presence of horizontal layers or horizons.
These layers are the result of a variety of processes.
Up to five different primary layers can be found: 0
- organic layer; A - topmost mineral that is rich in
organic matter and influence by eluviation; B - Illuviation
layer; C - layer not pedogenically developed; and R
- unweathered bedrock.
The process of soil
development is called pedogenesis. Pedogenesis is
the result of five factors: climate; living organisms;
parent material; topography; and time. Climate influences
soils by influencing rates of weathering, organic
matter decomposition, and soil chemical reactions.
Living organisms influence soil development through
organic matter accumulation, profile mixing, and
biogeochemical cycling. Parent material influences
soil texture, soil chemistry, and nutrient cycling.
Pedogenesis is influenced by topographyÕV,s
effect on microclimate and drainage. Time influences
the temporal consequences of all of the factors above.
At the macro-scale we can suggest that
there are five main principal pedogenic processes.
These processes are laterization, podzolization, calcification,
salinization, and gleization.
Soil classification systems have been
created to provide scientists and resource managers
with a system to determine the charateristics of a
soil in a particular location. Several different classification
systems exist. We are interested in two systems. The
United States Soil Classification System recogizes
eleven distinct soil orders: oxisols, aridsols, mollisols,
alfisols, ultisols, spodsols, entisols, inceptisols,
vertisols, histosols, and andisols. The Canadian System
of Soil Classification was designed to classify soils
that develop in Canada's cool climatic environment.
The Canadian System recognizes nine different orders:
Brunisols, Chernozems, Cryosols, Gleysols, Luvisols,
Organic, Podzols, Regosols, and Solonetzic.
Erosion is the removal and transport
of material from the surface of the Earth. The energy
from erosion comes from a variety of sources that generally
act because of gravity. Erosion normally involves three
processes: detachment, entrainment and transport. Detachment
usually begins the process of erosion. Sometimes it
can involve the breaking of bonds that hold particles
together. Entrainment is the operation of lifting particles
by and into the agent of erosion. Because most particles
bond with other particles more erosive energy is require
to lift a particle than to transport it. Transportation
of particles can occur in four different ways: suspension,
saltation, traction and solution. The exact mechanism,
which moves a particle, is dependent on the weight,
size, shape, and surface configuration of the grain
of sediment and the viscosity of the erosive agent.
Deposition occurs when the erosive agent
can no longer move, dissolve or suspend eroded particles.
In most cases, deposition requires a reduction in the
flow velocity of the erosive agent. It can also involve
evaporation, as in the case of dissolved ions in water,
or melting, as in the case of glacial erosion and transport.
For most particles deposition is not a onetime event.
Most particles under go repeated cycles of erosion
and deposition before they come to their final rest.
Most of the terrestrial landscape consists
of a mosaic of hillslope types. A number of geomorphic
processes act on these landforms causing them to be
worn and eroded over time. The erosion of hillslopes
ends, or reaches equilibrium, when the sediments and
rocks that make up hills are redistributed more evenly
on the Earth's surface. Geomorphologists tend to view
hillslope processes a series of system inputs and outputs.
Inputs to the hillslope system include sediments from
weathering, solar radiation, and water from precipitation.
Outputs occur by way of evapotranspiration, percolation,
groundwater flow, runoff, stream flow, and the flow
of glacial ice. Some of the above processes also move
sediment from hillslopes. The movement of sediments
through the hillslope system without the help of the
erosional mediums of wind, water and ice is know as
Mass wasting consists of a number of
processes whose action causes the downslope movement
of sediments. All of these processes are powered by
gravity. The development of hillslope instability and
mass wasting depends on a number of factors that influence
the stress exerted on sediments. If these stresses
greatly exceed the internal strength holding slope
materials in place the slope failure tends to be large
in size and rapid. Slow long-term failures develop
when the stresses acting on the hillslope just exceed
the internal strength of the slope materials. We can
group the various types of mass wasting into three
different groups based on the characteristic of the
slope materials. In slopes formed from non-cohesive
coarse-grained sediments mass wasting occurs by way
of: the sliding and rolling of individual particles;
through the chaotic avalanche or many particles; or
by the process of shallow sliding of a large number
of particles along a plane of weakness. Slopes formed
on cohesive materials like clay and silt have different
set of processes involved in their mass wasting. The
main processes of mass wasting on cohesive sediments
are rotational slips, mudflows and soil creep. A number
of hillslopes are composed of large masses of rock.
Rock normally has strong internal granular bonds allowing
slopes made of this material to maintain steep grades.
Mass wasting on hard rock slopes generally occurs along
bedding planes and joints found in the rock.
Streams modify the landscape through
the movement of water and sediment. Streams are very
powerful erosive agents especially during periods of
flooding. The sediments removed by streams are usually
deposited downstream in floodplains, lakes, and ocean
basins. Streams and their floodplains vary in their
characteristics along the typical long profile of a
stream. The grade of the long profile represents a
balance between erosion and deposition processes. At
the headwaters streams flow quickly (because of a steep
grade) in narrow v-shaped valleys. Depositional features
are rare. Further down the profile a profound change
occurs in the stream gradient. This change reduces
velocity causing the stream to drop its coarser sediments
in a floodplain. The channels of these streams is braided.
The gradient of the stream becomes very shallow in
the last part of the long profile. Now the stream channel
takes on meandering and floodplain deposits are spread
over a larrge area.
The amount water flowing through a stream
channel is commonly referred to as stream discharge.
Discharge quantity is controlled water velocity, width
of the channel, and the depth of the channel. These
variable also change with velocity increases or decreases
over time. Flow within the stream channel is allways
at a maximum at the center of the stream. The channel
bottom and banks reduce flow velocity because of friction.
In three-dimensions, the zone of maximum flow or thalweg
moves from side to side and up and down. A closer examination
of flow indicates that three types of flow occur: laminar
flow; turbulent flow; and helical flow.
All streams carry sediment. The actual
amount is related to the characteristics of the materials
on which the stream flows. Usually, an increase in
discharge results in an increase in the amount of sediment
that is carried.A sediment rating curve models the
relationship between discharge and the amount of sediment
carried. Now within the stream sediment can be carried
in three ways: bed load; suspended load; and dissolved
One of the most obvious landforms created
by streams are the channels they flow in. We can classify
stream channels into three types. Channels located
in the upper reach of streams are V-shaped, narrow,
and deep with little associated floodplain. These channels
are often cut into bedrock and limited bed sediments
consist loose rocks and boulders. Stream channels become
shallow, wide, and braided when the stream gradient
changes from being steep to gently sloping. Shallow
braided channels are created by the presence of sand
and gravel beds in a floodplain. These sediments are
deposited because a sudden change in gradients causes
a reduction in flow velocity. Often a drastic change
in grade also causes the deposition of an alluvial
fan. Channels become U-shaped and meandering with continued
reduction in stream gradient. Meandering channels flow
over an extensive floodplain of complex deposits.
We can describe a number of features
within the stream channel. Streams carrying coarse
loads develop sand and gravel beds when velocity is
reduced spatially or temporally. Point bars are common
in meandering streams devloping on the inside of channel
bends. In straight streams, bar deposits form in relation
to the thalweg. Some other features associated with
the thalweg include riffles and pools. Some other features
common within the stream channel are dunes and ripples.
These features form on the channel bottom when the
bed is composed of sand and silt.
Floodplains are flat areas adjacent to
stream channel that are composed primarily of deposits
put down during episodes of floods. A number of features
are found on the floodplain. Some of these features
are depositional like levees, abandoned point bars,
and depressions. Other features like crevasses and
Oxbow lakes are created by erosion.
When a stream ends its flow into a lake
or ocean the sediment it carries will be deposited
to create a delta. Deltas are complex features made
up of 3 different bed types. Deltas also have a variety
of different shapes.
Scientists often view streams as being
part of a drainage basins. Drainage basins are arbitrarily
defined by topography. Drainage basins are a very useful
geomorphic concept and they are oftem modeled as open
systems. Within a drainage basin inputs and factors
like topography, soil type, bedrock type, climate,
and vegetation influence a number of stream properties.
One stream property that is effected by these factors
is the drainage pattern of streams.
Stream morphometry is all about exploring
the mathematical relationships between various stream
attributes. Studies have discovered that these relationships
can be view as laws because of their geometric or mathematical
predictability. These measurements can also be used
to compare streams and basins to identify factors that
may be causing differences.
Landforms of coastal regions are in most
cases shaped by the geomorphic action of ocean waves.
Ocean was can exert a significant amount of energy
through the kinetic energy of wave motion. The energy
of ocean waves on the terrestrial landscape of the
Earth is concentrated at the shoreline. At the shoreline
the energy wave motion causes erosion and the transport
of sediment. Erosion along the shoreline is normally
greatest at areas where wave refraction causes the
intensification of wave energy. Deposition occurs along
the shoreline when wave energy is reduced in it intensity
and when sediment is transported into an area by beach
drift and longshore drift
During the last billion years of Earth
history there have been several periods where global
average temperatures were much colder than they are
today. The colder climates lead to the formation an
expansion of extensive continental and alpine glaciers.
The last period of glacial advance began about 2 million
years ago. For the past 14,000 years we have been experiencing
a warming of the global climate which has lead to a
retreat of glaciers. Today glaciers cover about 10
% of the Earth's land surface. During the height of
the last glacial advance about 30% of the Earth's
land surface was covered. Geomorphologists have classified
glaciers based on size.
The growth of glaciers first involves
the conversion of snow into glacial ice. This process
takes many years and the weight of overlying deposits
to covert snow with a density between 50 to 300 kilograms
per cubic meter to ice with a density of 850 kilograms
per cubic meter. For mass of ice to be classified as
a glacier it most have the ablity to move. This occurs
when the mass of ice becomes so heavy that it begins
to flow by plastic deformation. Masses of ice in mountain
valleys begin to flow when accumulations become more
than 20 meters high. Rates of flows within glaciers
is influenced by factors like friction, ice weight,
and slope of the valley. Some glaciers are able to
move more quickly because they experience basal sliding.
Scientists oftem view glaciers as systems
that are influenced by a number of inputs and outputs.
Some of these inputs and outputs influence the glaciers
ability to surge or retreat. The concept of glacier
mass balance suggests that a glacier is influenced
by two processes: accumulation and ablation. If accumulation
exceeds ablation the glacier surges forward. If ablation
exceeds accumulation the glacier surges retreats.
Glaciers have played an important role
in shaping the landscape of the middle and higher latitudes.
The effects of glaciers exist at essentially two scales.
Alpine glaciers modify landcapes on a local scale.
Many alpine glaciers are still operating today in the
world's mountainous regions. Continental glaciers influenced
landscapes on the regional and continental scale. Most
of these glaciers are now gone, but the evidence of
their action is still quite obvious.
Glacial landforms that are the result
of erosion can once again occur at two scales. On the
local scale, alpine glaciers are responsible for the
following erosional features: U-shaped valleys, hanging
valleys, cirques, horns, and aretes. Continential glaciers
removed large amount of surface sedments on the areas
that they occurred. Sometimes this removal of material
left large depression which are now filled with lakes
of all sizes. Both types of glaciers leave the following
depositional features: till, moraines, outwash plains,
and erratics. The size of these deposits is of course
much large for the continental glaciers. Continental
glaciers also produce a number unique deposits like:
kame, eskers, and drumlins.
About 25% of the Earth's terrestial
surface is influenced by periglacial processes. The
most important process of periglacial environments
is freeze-thaw action. Extreme cold temperatures of
periglcial environments often causes surface soils
and sediments to freeze. These frozen sediments are
called permafrost. Many types of permafrost have been
classified. Permafrost can have a depth of up to 1500
meters. On its surface, is a layer that is subject
to seasonal thawing. This layer is called the active
layer. Sheets of permafrost can have unfrozen layers
on top, beneath, or within it. These unfrozen layers
are called taliks.
Periglacial areas are also known for
the presence of ground ice. Ground ice comes in a variety
of differnt forms and each type has unique characteristics
and processes of formation. A number of geomorphic
processes operate in periglacial regions. One process
that is quite active in periglacial regions is physical
weathering due to the crystallization of water. This
process can create vast quantities of shattered angular
rock on the periglacial landscape. Mass movement is
common in periglacial regions of the world. The main
processes that resulting mass movement include solifluction,
gelifluction, frost creep, and rockfalls. Finally,
erosion occurs in periglacial environment by way of
nivation, eolian processes, and fluvial processes.
Three types of landforms are common in
periglacial environments. The first is patterned ground.
Pattern gound comes in a variety of shapes including
stripes, steps, circles, polygons, and nets. A number
of processes are involved in the formation of these
similar features. Periglacial environments are also
characterized by the presence of ice mounds. Palsas
are low elongated mounds with cores of segregated ice
and peat. The other type of ice cored hill is called
a pingo. These features are much larger than palsas
and are formed by either cryostatic pressure or artesian
Places in the arid regions and coastal
areas of the world are influence by wind. The speed
of these winds is great enough to move soil particles
that range in size from clay to sand. Material is transport
by wind by three processes: traction, saltation, and
suspension. The power of wind produces a variety of
eolian erosional features. Some of these features include
deflation hollows, pans, and desert pavement. Wind
also produces a variety of deposional features. Sand
dune are the most noticable feature of deposition.
Sand dunes come in a variety of forms that are produced
by a range of processes.Another important deposit of
eolian forces is loess. Many deposits of loess were
formed in the past when winds blew over glacial deposits
during the pleistocene.
List of Key Terms
Ablation, Abrasion, Abyssal
Fan, Accretion, Accumulation, Acidic, Acidic
Layer, Aftershock, Aggradation, A
Horizon, Alkaline, Allophane, Alluvial
Fan, Alluvium, Alpine
Permafrost, Amphibole, Andesite, Anticline, Arêtes, Arkose, Artesian, Asthenosphere, Atmosphere, Atom,
Backwash, Bacteria, Bank-Caving, Bar, Barrier
Sliding, Basalt, Basalt
Rock, Basic, Batholith, Bay, Bayhead
Bar, Beach, Beach
Drift, Bed, Bed Load, B
Weathering, Biosphere, Biotite, Blowout, Body
Bed, Boulder, Bowen
Reaction Series, Braided
Stream, Breaker, Breccia,
Carbonate, Caldera, Caldera
Volcano, Caliche, Calving, Canadian Shield, Canyon, Carbonation, Cation, Cave, Cavitation, Cenozoic, Chalk, Chelate, Chelation, Chemical
Cone, Cirque, Cirque
Glacier, Clastic, Clay, Cleavage, Closed
Talik, Coal, Cold
Volcano, Compound, Conduction, Conglomerate, Coniferous Vegetation, Contact
Glacier, Continental Margin, Continental
Plate, Continental Rise, Continental
Shelf, Continental Shelf Break, Continental
Permafrost, Convection, Core, Craton, Creep, Cretaceous, Crevasse, Critical
Entrainment Velocity, Crust, Cryostatic Pressure, Cuspate
Flow, Decomposition, Deflation Hollow, Delta, Density, Deposition, Depositional
Landform, Depression, Desert
Pavement, Detachment, Diorite, Dip, Discontinuous
Load, Disturbance, Dolomite, Drainage
Density, Drumlin, Dune, Dune
Field, Dyke, Dynamic
Focus, Ecosystem, Eddy, Element, Eluviation, Energy, Entrainment, Eon, Epicenter, Epoch, Equilibrium, Era, Erosion, Erosional Landform, Erratics, Esker, Eukaryotic, Evaporation, Evapotranspiration, Evaporite, Evolution, Extrusive
Fault, Faulting, Feldspar, Felsic
Magma, Ferricrete, Fetch, Firn, Firn
Limit, Fissure, Flocculation, Flood, Floodplain, Fluid
Drag, Fold, Folding, Foliation, Food
Chain, Foreset Bed, Forminifera, Freeze-Thaw
Action, Friction, Frost
Creep, Frost Wedging,
Gabbro, Gelifluction, Glacial, Geologic
Time Scale, Glacial
Surge, Glacier, Glaciofluvial, Gneiss, Graben
Fault, Granite, Granitic Magma, Granitic
Pluton, Grasslands, Gravel, Gravity, Ground
Ice, Groundwater, Groundwater
Valley, Headland, Headwaters, Helical
Epoch, Horn, Horst
Fault, Humus, Hydration, Hydrocarbon, Hydrolysis, Hydrosphere,
Rock, Illuviation, Infiltration, Inner
Core, Inorganic, Insolation
Weathering, Interglacial, Intrusive
Igneous Rock, Ion, Island
Arc, Isostacy, Isostatic
Kame, Karst, Kettle
Landslide, Laurasia, Lava
Flow, Lignite, Limestone, Lithification, Lithosphere, Lithospheric Hot
Flow, Lateral Moraine, Laterite, Law of Basin Areas, Law
of Stream Lengths, Law of Stream Numbers, Leaching, Lee-Side, Leeward, Levee, Limestone, Lithification, Lithosphere, Litter, Litterfall, Little Ice Age, Littoral
Drift, Lobe, Loess, Longshore
Magma, Magma, Magma
Plume, Magnitude, Mantle, Marble, Mass
Wasting, Metamorphic Rock, Metamorphism, Metasomatic
Metamorphism, Mica, Mid-Oceanic
Ridge, Mineral, Monocline, Mudstone, Muscovite,
Magma, Mass, Mass Balance, Mass
Wasting, Meander, Medial
Moraine, Melting, Meltwater, Metamorphism, Mid-Latitude Cyclone, Mineral, Moraine, Mountain
Glacier, Mouth, Morphometry, Mudflow,
Feedback, Névé, Nivation, Nivation
Trench, Olivine, Organic
Matter, Orogeny, Outer
Matter, Outwash, Outwash
Plain, Oxidation, Overbank
Flow, Oxbow Lake,
Paleoclimatic, Pangaea, Peridotite, Period, Permian, pH, Phanerozoic, Plagioclase
Tectonics, Platform, Pleistocene, Pluton, Plutonic Igneous
Energy, Precambrian, Precipitation, Process-Response
System, Prokaryotic, Pyroxene, P-wave,
Paleoclimatic, Palsa, Pan, Patterned
Ground, Peat, Pebble, Pedogenesis, Percolation, Periglacial, Permafrost, pH, Physical
Glacier, Pingo, Plate
Tectonics, Pleistocene, Plucking, Podzolization, Point
Bar, Pools, Pore
Energy, Precipitation, Pressure
Quartz, Quartzite, Quaternary,
Fault, Rhyolite, Richter
Zone, Rock, Rock
Impact, Rainsplash, Rainwash, Recessional Moraine, Reduction, Reg, Regolith, R
Horizon, Riffles, Rill, Rip
Current, Ripples, Roche Moutonnee, Rock, Rockfall, Rock
Sand, Sandstone, Schist, Sea-Floor
Spreading, Sea-Level, Sedimentary Rock, Seismic, Seismic
Wave, Seismograph, Shale, Shield, Shield
Volcano, Silica, Silicate
Magma, Silcrete, Sill, Silt, Siltstone, Slate, Stream
Landform, Subduction, Subduction
Zone, Submarine Canyon, Subsidence, Surface
Wave, Syncline, S-wave, Salinization, Saltation, Sand, Sand
Wedge, Scree, Sea
Stack, Sediment, Sedimentary
Rating Curve, Seepage, Segregated
Wave, Shale, Sheetwash, Shore, Shoreline, Silicate, Silt, Slaking, Snout, Snow, Snow
Melt, Soil, Soil
Radiation, Solifluction, Solution, Specific
Heat, Spit, Sporadic
Permafrost, Spring, Steady
State, Stoss-Side, Stream, Steam
Long Profile, Striations, Sublimation, Subsea
Load, Suspension, Swash, Swell, System,
Tectonic Plate, Tephra, Tertiary, Tetrahedron, Thermal
Talik, Talus, Talus
Cone, Temperate Glacier, Terminal
Fall Velocity, Terminal
Velocity, Terminus, Thalweg, Threshold
Velocity, Throughflow, Through
Talik, Thunderstorms, Tidal
Current, Till, Till
Plain, Tombolo, Topset Bed, Traction, Transport, Turbulent
Unloading, Ultramafic, Uniformitarianism, Upper
Igneous Rock, Volcanic
Pipe, Volcano, Vortice,
Watershed, Water Table, Wave, Wave
Height, Wavelength, Wave
Period, Wave Refraction, Wave
Trough, Weathering, Weathering
and Drying, Wind
of Ablation, Zone
Study Questions, Problems,
(1). Discuss in detail the formation
of sedimentary rocks. Also, include in your answer
information concerning their composition, lithification,
(2). Explain why the theory of plate
tectonics explains lithospheric phenomena like earthquakes,
mountains, volcanoes, folding, and faulting.
(3). Compare and contrast the structure,
composition, and formation of igneous and sedimentary
(4). Discuss the classification of
clastic sedimentary rocks according to particle types.
(5). Outline the Bowen reaction series.
What does it tell us about the formation of minerals
in igneous rocks?
(6). What geologic features are found
at the boundaries of tectonic plates? Briefly explain
how plate tectonics is responsible for their formation
(7). What evidence exists for the theory
of plate tectonics
(8). Describe the various types of
igneous rocks that exist according crystal size,
magma chemistry, and the quantity of various mineral
(9). Discuss how heat, pressure, and
the chemical action of fluids act to create metamorphic
rocks. Describe some of the common types of metamorphic
(10). What is the difference between
clastic and non-clastic sedimentary rocks? What are
the two general types of non-clastic sedimentary
rocks that exist? Finally, give two examples of each
of these three rock types.
(11). What are the eight most common
elements found in minerals? Describe the nine major
groups of minerals.
(12). Describe the various layers that
make up the solid Earth.
(13). Describe the various physiological
features associated with the ocean basins.
(14). What is a volcano? Where and
why do they form? Describe the five different types
(15). Describe the various physiological
features associated with the Earth's terrestial surface.
(16). Describe the various physiological
features associated with the Earth's ocean basins.
(17). Outline the various
processes of physical, chemical, or biological weathering.
(18). Erosion can be seen
as three processes: detachment, entrainment and transport.
Discuss these three processes in relation to following
two erosional mediums: water and ice.
(19). Discuss the nature
of hillslope failure processes as related to cohesive
and non-cohesive materials slope materials.
(20). Describe the physical
characteristics of a location that would favor each
of the following types of mass movements: rockfall,
rockslide, mudflow, slump, and creep.
(21). What is a glacier?
What conditions are necessary for a glacier to form?
Why did continental glaciers form over certain specific
regions of the North American continent?
(22). Describe the overall
impact of extensive alpine glaciation on the mountainous
regions of British Columbia. What are some of the
more important erosional and depositional landforms?
(23). By what processes
do waves and currents erode coasts? Briefly describe
(24). What coastal environmental
conditions favor coastal erosion? What conditions
favor coastal deposition?
(25). How do glaciers
influence the surface configuration of the Earth
by way of erosion and deposition? Give plenty of
examples in your answer.
(26). What are some of
the common features associated with continental glaciation?
How are these features formed?
(27). Briefly describe
SIX depositional features associated with continental
(28). How does beach drift
and longshore drift move sediment along coastlines?
(29). What factors often
trigger mass movement?
(30). Describe the various
processes that operate in periglacial regions.
(31). Describe the common
landforms found in periglacial regions.
(32). Describe some of
the landforms common to environments influenced by
(33). Describe some the
important characteristics of soil.
(34). What five factors
are important in pedogenesis? Explain. Outline how
the pedogenic processes operate.
(35). Describe the Canadian
and US systems of soil classification.