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GEOMORPHOLOGY 1

CODE: 103

1- Introductiona- Backgroundb- Fundamental Concept in Geomorphologyc- Scope

2- Structure of the Earth and Internal Energya- Coreb- Mantlec- Earths Lithosphere and Crust

3- Movements of the Earths Crusta- Plate Tectonicsb- Continental Drift Theory

4- Rocks and Mineralsa- Igneous b- Sedimentary c- Metamorphic d- Rock cyclee- Identification of rocks

5- Forces of the Earths Crusta- Exogenic

i- Mountainsii- Plainsiii- Plateaus

b- Endogenici- Earthquakesii- Volcanoes

6- External Geomorphic Processesa- Weatheringb- Mass Wasting

Chapter One:

Introduction to Geomorphology

Geomorphology is the study of the Earth's surface landforms both on land and on the sea floor. This study is

both descriptive and quantitative; it deals with morphology, processes, and origins of landforms. The ultimate

goals of geomorphology are to understand the way in which landforms are created and to document theevolution of landforms through time. The geomorphology of any region or site is the result of interplay

involving three primary factors.


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1. Structure: refers to the nature of solid materials that form the surface and subsurface, their compositiontexture, fabric, architecture, mechanical strength, and other physical attributes.

2. Process: refers to the physical, chemical, biological or human processes that shape the surface intolandforms. Broadly speaking, processes are either depositional (constructive) or erosional (destructive).

3. Time: refers both to the rate at which a process modifies the surface and to the length of time orduration that a process has operated at a site.

All Earth surfaces are subject to diverse processes that operate at greatly varying rates. Static landscapes do not

exist; all landscapes undergo constant modificationsome quite slowly, others rapidly, and almostinstantaneously in certain cases. The active processes also change through time, so that every landscape issubject to continual evolution.


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Chapter Two:

Structure of the Earth and Internal Energy

a- Coreb- Mantlec- Earths Lithosphere and Crust

The Earth is an oblate spheroid. It is composed of a number of different layers as determined by deep drillingand seismic evidence. These layers are:

The core, which is approximately 7,000 kilometers in diameter (3,500 kilometers in radius) and islocated at the Earth's center.

The mantle, which surrounds the core and has a thickness of 2,900 kilometers. The crust, which floats on top of the mantle. It is composed of basalt rich oceanic crust and granitic rich

continental crust.

The Core:

The core is a layer rich in iron and nickel that is composed of two layers: the inner and outer cores. The inner

core is theorized to be solid with a density of about 13 grams per cubic centimeter and a radius of about 1,220

kilometers. The outer core is liquid and has a density of about 11 grams per cubic centimeter. It surrounds theinner core and has an average thickness of about 2,250 kilometers.

Figure: Structure of the Earth's crust and top most layer of the upper mantle. The lithosphere consists of the oceanic crust, continental

crust, and uppermost mantle. Beneath the lithosphere is the asthenosphere. This layer, which is also part of the upper mantle, extends

to a depth of about 200 kilometers. Sedimentary deposits are commonly found at the boundaries between the continental and oceanic

crust. (Source: PhysicalGeography.net)

Mantle:

The mantle is almost 2,900 kilometers thick and comprises about 83% of the Earth's volume. It is composed ofseveral different layers. The upper mantle exists from the base of the crust downward to a depth of about 670

kilometers. This region of the Earth's interior is thought to be composed of peridotite, an ultramafic rock made

up of the minerals olivine and pyroxene. The top layer of the upper mantle, 100 to 200 kilometers below
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surface, is called the asthenosphere. Scientific studies suggest that this layer has physical properties that aredifferent from the rest of the upper mantle. The rocks in this upper portion of the mantle are more rigid and

brittle because of cooler temperatures and lower pressures. Below the upper mantle is the lower mantle that

extends from 670 to 2,900 kilometers below the Earth's surface. This layer is hot and plastic. The higherpressure in this layer causes the formation of minerals that are different from those of the upper mantle.

Lithosphere/Crust:

The lithosphere is a layer that includes the crust and the upper most portion of the asthenosphere. This layer isabout 100 kilometers thick and has the ability to glide over the rest of the upper mantle. Because of increasing

temperature and pressure, deeper portions of the lithosphere are capable of plastic flow over geologic time. The

lithosphere is also the zone of earthquakes, mountain building, volcanoes, and continental drift.
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Figure: The addition of glacial ice on the Earth's surface causes the crust to deform and sink (a). When the ice melts, isostatic rebound

occurs and the crust rises to its former position before glaciation (b and c). A similar process occurs with mountain building and

mountain erosion. (Source: PhysicalGeography.net)

The topmost part of the lithosphere consists of crust. This material is cool, rigid, and brittle. Two types of crust

can be identified: oceanic crust and continental crust. Both of these types of crust are less dense than the rockfound in the underlying upper mantle layer. Ocean crust is thin and measures between 5 to 10 kilometers thick.

It is also composed of basalt and has a density of about 3.0 grams per cubic centimeter.

The continental crust is 20 to 70 kilometers thick and composed mainly of lighter granite. The density of

continental crust is about 2.7 grams per cubic centimeter. It is thinnest in areas like the Rift Valleys of East

Africa and in an area known as the Basin and Range Province in the western United States (centered in Nevadathis area is about 1,500 kilometers wide and runs about 4,000 kilometers North/South). Continental crust is

thickest beneath mountain ranges and extends into the mantle. Both of these crust types are composed of

numerous tectonic plates that float on top of the mantle. Convection currents within the mantle cause theseplates to move slowly across the asthenosphere.

Isostacy

One interesting property of the continental and oceanic crust is that these tectonic plates have the ability to rise

and sink. This phenomenon, known as isostacy, occurs because the crust floats on top of the mantle like ice

cubes in water. When the Earth's crust gains weight due to mountain building or glaciation, it deforms and sinksdeeper into the mantle. If the weight is removed, the crust becomes more buoyant and floats higher in the

mantle. This process explains recent changes in the height of sea-level in coastal areas of eastern and northern

Canada and Scandinavia. Some locations in these regions of the world have seen sea-level fallen by as much asone meter over the last one hundred years. This change is caused by isostatic rebound moving the land surface

upwards relative to sea-level. Both of these areas where covered by massive glacial ice sheets about 10,000

years ago. The weight of the ice sheets pushed the crust deeper into the mantle. Now that the ice is gone, these

land areas are slowly increasing in height to some new equilibrium level.
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Chapter 3

Movements of the Earths Crust

a- Plate Tectonicsb- Continental Drift Theory

The Story of Plate Tectonics

The story ofPlate Tectonics is a fascinating story of continents drifting majestically from place to place

breaking apart, colliding, and grinding against each other; of terrestrial mountain ranges rising up like rumplesin rugs being pushed together; of oceans opening and closing and undersea mountain chains girdling the planet

like seams on a baseball; of violent earthquakes and fiery volcanoes. Plate Tectonics describes the intricate

design of a complex, living planet in a state of dynamic flux.

Plate tectonics: The main features are:

The Earth's surface is made up of a series of large plates(like pieces of a giant jigsaw puzzle).

These plates are in constant motion travelling at a fewcentimetres per year.

The ocean floors are continually moving, spreading fromthe centre and sinking at the edges.

Convection currents beneath the plates move the platesin different directions.

The source of heat driving the convection currents isradioactive decay which is happening deep in the Earth.

The edges of these plates, where they move against eachother, are sites of intense geologic activity, such asearthquakes, volcanoes, and mountain building.

Plate tectonics is a relatively new theory and it wasn'tuntil the 1960's that Geologists, with the help ofocean

surveys, began to understand what goes on beneath our

feet.
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Where is the Evidence for Plate Tectonics?

The continents seem to fit together like a giant jigsaw puzzle:

If you look at a map, Africa seems to snuggle nicely into

the east coast of South America and the Caribbean sea. In1912 a German Scientist called Alfred Wegener proposed

that these two continents were once joined together then

somehow drifted apart. He proposed that all the continentswere once stuck together as one big land mass called

Pangea. He believed that Pangea was intact until about 200

million years ago

Continental Drift Theory:

The idea that continents can drift about is called, notsurprisingly, Continental Drift.When Wegener first put

forward the idea in 1912 people thought he was nuts. His

big problem was that he knew the continents had drifted but

he couldn't explain how they drifted. The old (AND VERYWRONG!!) theory before this time was the "Contraction

theory" which suggested that the planet was once a molten

ball and in the process of cooling the surface cracked andfolded up on itself. The big problem with this idea was that

all mountain ranges should be approximately the same age,

and this was known not to be true. Wegener's explanationwas that as the continents moved, the leading edge of the

continent would encounter resistance and thus compress

and fold upwards forming mountains near the leading edges

of the drifting continents. Wegener also suggested that

India drifted northward into the Asia forming theHimalayas and of course Mount Everest.

Sea Floor Spreading:

It is hard to imagine that these great big solid slabs of rock could wander around the globe. Scientists needed a

clue as to how the continents drifted. The discovery of the chain of mountains that lie under the oceans was theclue that they were waiting for.

Plates are Created:

The diagrams show that the continental crust is beginning to separate creating a diverging plate boundary.When a divergence occurs within a continent it is called rifting. A plume of hot magma rises from deep within

the mantle pushing up the crust and causing pressure forcing the continent to break and separate. Lava flowsand earthquakes would be seen. In the diagram below you can see that the continental crust is beginning to

separate creating a diverging plate boundary. When a divergence occurs within a continent it is called rifting. A

plume of hot magma rises from deep within the mantle pushing up the crust and causing pressure forcing thecontinent to break and separate. Lava flows and earthquakes would be seen.
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This is an example of a divergent plate boundary

(where the plates move away from each other). The

Atlantic Ocean was created by this process. The mid-

Atlantic Ridge is an area where new sea floor is beingcreated.

As the rift valley expands two continental plates havebeen constructed from the original one. The molten

rock continues to push the crust apart creating new

crust as it does.

As the rift valley expands, water collects forming a sea.

The Mid-Atlantic Ridge is now 2,000 metres above the

adjacent sea floor, which is at a depth of about 6,000

metres below sea level.

The sea floor continues to spread and the plates

get bigger and bigger. This process can be seen

all over the world and produces about 17 squarekilometres of new plate every year.

Picture the following in your mind:

1. You have a nine piece jigsaw.2. The piece in the middle starts to grow.3. It gets bigger and bigger.

What do you think will happen to the puzzle?

Now let's think back to our plates being created at the mid-ocean ridges, it seems to be a good idea but if this is

the only type of plate movement then the world would get bigger and bigger. In fact the world has remained thesame size. So if plates are being created at the mid-ocean ridges then they must be being consumed somewhere

else in the world.

Plates are Destroyed (SUBDUCTION):This is a convergent plate boundary, the plates move

towards each other. The amount of crust on the surfaceof the earth remains relatively constant. Therefore,

when plates diverge (separate) and form new crust inone area, the plates must converge (come together) in

another area and be destroyed. An example of this is the

Nazca plate being subducted under the South Americanplate to form the Andes Mountain Chain.

Here we can see the oceanic plate moving from left to right. The top layer of the mantle and the crust (all calledthe lithosphere) sinks beneath the continent. A deep ocean trench is formed. Water gets carried down with the


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oceanic crust and the rocks begin to heat up as they travel slowly into the earth. Water is then driven off

triggering the formation of pools of molten rock which slowly rises. The plate moves downwards at a rate of afew centimetres per year. The molten rock can take tens of thousands of years to then either:

Solidify slowly underground as intrusive igneous rock such as granite.or

Reach the surface and erupt as lava flows. Cooling rapidly to form extrusive igneous rock such asbasalt.

The floor of the Easter Pacific is moving towards South America at a rate of 9 centimetres per year. It might not

seem much but over the past 10 million years the Pacific crust has been subducted under South America and has

sunk nearly 1000 kilometres into the Earth's interior.

Types of Convergent Boundaries

The example above showed what happened when the dense oceanic plate subducts under a lighter continental

plate (ie, oceanic - continental). Two other types of subduction can take place:When two oceanic plate meet each other (oceanic-

oceanic) this often results in the formation of an island

arc system. As the subducting oceanic crust melts as it

goes deeper into the Earth, the newly-created magmarises to the surface and forms volcanoes. If the activity

continues, the volcano may grow tall enough to breech

the surface of the ocean creating an island.

The key to subduction seems to be water which acts as a kind of lubricant as the heavier plate slips underneath

the lighter plate. Examples of such type of subduction are the Himalayas and Mount Everest.

Millions of years ago India and an ancient ocean called the Tethys

Ocean were sat on a tectonic plate. This plate was moving northwards

towards Asia at a rate of 10 centimetres per year. The Tethys oceaniccrust was being subducted under the Asian Continent. The ocean got

progressively smaller until about 55 milion years ago when India 'hit'

Asia. There was no more ocean left to lubricate the subduction and sothe plates welled up to form the High Plateau of Tibet and theHimalayan Mountains. The continental crust under Tibet is over 70

kilometres thick. North of Katmandu, the capital of Nepal, is a deep

gorge in the Himalayas. The rock here is made of schist and granitewith contorted and folded layers of marine sediments which were

deposited by the Tethys ocean over 60 million years ago.


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The fourth type of plate movement involves plates sliding past one another without the construction or

destruction of crust. This boundary is called a conservation zone because plate is neither created nor destroyedAn example of such a boundary is the San Andreas fault in California. The force needed to move billions of

tonnes of rock is unimaginable. When plates move some of the energy is released as earthquakes.

The Continental Drift Theory:

The continental drift theory is the theory that once all the continents were joined in a super-continent, which

scientists call Pangaea. Over a vast period of time, the continents drifted apart to their current locations. AlfredWegener first supported continental drift.

Wegeners explanation of continental drift in 1912 was that drifting occurred because of the earths rotation

This explanation and his theory were not widely accepted. Prior to Wegener, however, many had noted that theshapes of the continents seem to fit together, suggesting some schism in the past.

Before the 1950s, the concept of the continental drift, for the most part, was not even entertained as plausible. In

the 1950s and the years that followed, however, geologists began to consider the theory, and in the 1960s, most

geologists came to accept that the theory may well be possible. Several factors point to the change in acceptingthe continental drift theory.

Fossil records from separate continents, particularly on the outskirts of continents show the same species. As

well mineral specimens along the supposed break lines of the continents are nearly identical. Some identical

species exist on certain continents, like an earthworm common to both Africa and South America suggesting the

species could not have spontaneously arisen on both continents without some variations.

Continental drift theory also gained in popularity because of the theory of plate tectonics. Briefly, plate

tectonics suggests that the ocean floor began to spread and that the continents existed on plates that moved in

response to the changing ocean floor. Disruption in the continents, such as earthquakes, were a response to themoving plates. This suggests that certain points of the continents exhibit almost constant, though tiny

movements.

For example, Point Reyes, which is located on the San Andreas Fault line in Northern California, has beenmeasured as slowly moving north at a rate of about half an inch (about 2.5 cm) per year. In fact, somegeologists theorize that with continued movement, Point Reyes might eventually become an island.

Not everyone accepts the continental drift theory for many reasons. One reason for the dispute is that the age of

the earth is in dispute. Some creationists, for example, believe that the earth is far younger than supposed somegeologists believe. Some of these creationists also do not accept carbon dating as a way of determining earth, or

fossil records being as old as some scientists claim.

Most scientists, and those not believing in creationism, accept the continental drift theory, along with the theory

of plate tectonics. Those endorsing the theory of intelligent design usually accept continental drift as well, but

assert that a spiritual presence designed and created the earth. Continental drift theory is now taught as acceptedtheory in public schools throughout the US.
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Chapter 4:

Rocks and Minerals

a- Igneousb- Sedimentaryc- Metamorphicd- Rock cyclee- Identification of rocks

THE EARTH'S CRUST

The whole earth is made of rocks & minerals. Inside the earth there is a liquid core of

molten rock and on the outside there is a hard crust. If you compare the earth to an egg, the

shell on an egg is like the crust on the earth. The crust is made up of rocks and minerals.

Much of the crust is covered by water, sand, soil and ice. If you dig deep enough, you will

always hit rocks. Below the loose layer of soil, sand & crumbled rocks found on Earth is

bedrock, which is a solid rock.

ROCKS

The rocks you see around you - the mountains, canyons & riverbeds, are all made of

minerals. A rock is made up of 2 or more minerals. Think of a chocolate chip cookie as a

rock.The cookie is made of flour, butter, sugar & chocolate. The cookie is like a rock and

the flour, butter, sugar & chocolate are like minerals. You need minerals to make rocks, but

you don't need rocks to make minerals. All rocks are made of minerals.

MINERALS

A mineral is composed of the same substance throughout. If you were to cut a mineral sample, it would look thesame throughout.

There are about 3000 different minerals in the world. Minerals are made of chemicals - either a single chemical

or a combination of chemicals.

There are 103 known chemical elements. Minerals are sorted into 8 groups. Some common examples have been

listed for each.

Native Elements ~ copper, silver, gold, nickel-iron, graphite, diamond

Sulfides ~ sphalerite, chalcopyrite, galena, pyrite

Halides ~ halite, fluorite

Oxides & Hydroxides ~ corundum, hematite

Nitrates, Carbonates, Borates ~ calcite, dolomite, malachite

Sulfates, Chromates, Molybdates, Tungstates ~ celestite, barite, gypsum

Phosphates, Arsenates, Vanadates ~ apatite, turquoise

Silicates ~ quartz, almandine garnet, topaz, jadeite, talc, biotite mica
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CRYSTALS

Crystals are minerals that have had the chance to grow in the shape that they were

meant to be. Just like your DNA determines the colour of your eyes, how tall you will

get to be and the shape of your bones, the chemicals that a mineral is made of

determines what shape it gets to be. We can tell different minerals apart by what crystal

shape they are.

Sometimes minerals form in spaces where there is not a lot of room, so they don't have a

crystal shape. When there is just a big hunk of a mineral, it is called a massive mineral.

If there is a definite shape with easy to see flat sides, it is called a mineral crystal.

Most of the earth's crystals were formed millions of years ago. Crystals form when the

liquid rock from inside the earth cool and harden. Sometimes crystals form when liquids

underground find their way into cracks and slowly deposit minerals. Most mineral

crystals take thousands of years to "grow" but some like salt (halite) can form so quickly

that you can watch them grow at home! Some people think of crystals as clear pretty

rocks that are used for jewelry. Amethyst is a very common quartz crystal.

SOIL, SAND & DIRT

When rocks break down into smaller & smaller pieces, they turn into sand. If you look at the sand under a

microscope, you will see that sand is made up of the same minerals as the rocks that the sand came from. When

plants start to sprout up in sand, it is turning from being just small bits of rock to being soil.

Soil is very important to life on earth. It supports plant life. We could not live without plants. Soil is made up of

sand and decomposing plants and animals. Soil has many names including: clay, silt, mud, dirt, topsoil, dust,

potting soil and humus

THE ROCK CYCLE

Rocks are constantly being formed, worn down and then formed again. This is known as the Rock Cycle. It is

like the water cycle but it takes a lot longer. It takes thousands and millions of years for rocks to change. Rocks

are divided into 3 types. They are classified by how they were formed.

IGNEOUS

SEDIMENTARY

METAMORPHIC

IGNEOUS ROCKS

Igneous means made from fire or heat. When volcanoes erupt and the liquid rock comes up to the

earth's surface, then new igneous rock is made. When the rock is liquid & inside the earth, it is

called magma. When the magma gets hard inside the crust, it turns into granite. Most mountains

are made of granite. It cools very slowly and is very hard.When the magma gets up to the surface

and flows out, like what happens when a volcano erupts, then the liquid is called lava. Lava flows

down the sides of the volcano.
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When it cools & turns hard it is called obsidian, lava rock or pumice - depending on what it looks

like.

Igneous rocks form when molten lava (magma) cools and turn to solid rock. The magma

comes from the Earths core which is molten rock. The core makes up about 30% of the

Total Earth Mass (31.5%)

Obsidian is natures glass. It forms when lava cools quickly on the surface. It is glassy and

smooth.

Pumice is full of air pockets that were trapped when the lava cooled when it frothed out

onto the surface.

It is the only rock that floats.

There are 5 kinds of igneous rocks, depending on the mix of minerals in the rocks.

Granite contains quartz, feldspar & mica

Diorite contains feldspar & one or more dark mineral. Feldspar is dominant.

Gabbro contains feldspar & one or more dark mineral. The dark minerals are dominant.

Periodotite contains iron and is black or dark.

Pegmatite is a coarse-grained granite with large crystals of quartz, feldspar and mica.

SEDIMENTARY ROCKS

When mountains are first formed, they are tall and jagged like the Rocky Mountains on the west

coast of North America. Over time (millions of years) mountains become old mountains like the

Appalachian Mountains on the east coast of Canada and the United States. When mountains areold, they are rounded and much lower. What happens in the meantime is that lots of rock gets worn

away due to erosion. Rain, freeze/thaw cycle, wind and running water cause the big mountains to

crumble a little bit at a time.Eventually most of the broken bits of the rock end up in the streams &

rivers that flow down from the mountains. These little bits of rock & sand are called sediments.

When the water slows down enough, these sediments settle to the bottom of the lake or oceans they

run into. Over many years, layers of different rock bits settle at the bottom of lakes and oceans.

Think of each layer as a page in a book. One piece of paper is not heavy. But a stack of telephone

books is very heavy & would squish anything that was underneath. Over time the layers of sand and

mud at the bottom of lakes & oceans turned into rocks.These are called sedimentary rocks.

Some examples of sedimentary rocks are sandstone and shale. Sedimentary rocks often have fossils

in them. Plants & animals that have died get covered up by new layers of sediment and are turned

into stone. Most of the fossils we find are of plants & animals that lived in the sea. They just settled

to the bottom. Other plants & animals died in swamps, marshes or at the edge of lakes.

They were covered with sediments when the size of the lake got bigger.

When large amounts of plants are deposited in sedimentary rocks, then they turn into carbon. This
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gives us our coal, oil, natural gas and petroleum. A large sea once covered the central part of

Canada and the climate was very tropical. In time, sedimentary rocks formed there. That is why we

find dinosaur fossils in Alberta and the area is a good source of natural fuels.

Sedimentary rocks cover 75% of the earths surface. Most of the rocks found on the Earthssurface is sedimentary even though sedimentary rocks only make up less than 5% of all the

rocks that make up Earth.When rocks are exposed to the elementsair, rain, sun, freeze/thaw cycle, plantserosion

occurs and the little bits of rock worn away get deposited as sediments. Over time, thesesediments harden as they get buried by more sediments and turn into sedimentary rocks.Sedimentary rocks are usually formed in layers called strata.

There are 6 main kinds of sedimentary rocks depending on the appearance of the rock.

Conglomerate rock has rounded rocks (pebbles, boulders) cemented together in a matrix.Sandstone is a soft stone that is made when sand grains cement together. Sometimes the

sandstone is

deposited in layers of different colored sand.

Shale is clay that has been hardened and turned into rock. It often breaks apart in large flatsections.

Limestone is a rock that contains many fossils and is made of calcium carbonate &/or

microscopic shells.Gypsum, common salt or Epsom salt is found where sea water precipitates the salt as thewater evaporates.

Breccia has jagged bits of rock cemented together in a matrix.

METAMORPHIC ROCKS

Metamorphic rocks are rocks that have changed. The word comes from the Greek "meta" and "morph"

which means to change form.

Metamorphic rocks were originally igneous or sedimentary, but due to movement of the earth's crust,

were changed. If you squeeze your hands together very hard, you will feel heat and pressure. When the

earth's crust moves, it causes rocks to get squeezed so hard that the heat causes the rock to change.

Marble is an example of a sedimentary rock that has been changed into a metamorphic rock.

Metamorphic rocks are the least common of the 3 kinds of rocks. Metamorphic rocks are igneous

or sedimentary rocks that have been transformed by great heat or pressure.

Foliated metamorphic rocks have layers, or banding.

Slate is transformed shale. It splits into smooth slabs.Schist is the most common metamorphic rock. Mica is the most common mineral.

Gneiss has a streaky look because of alternating layers of minerals. Non-foliated

metamorphic rocks are not layered.

Marble is transformed limestone.

Quartzite is very hard.
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Chapter 5

Forces of the Earths Crust

a- Exogenici- Mountainii- Plainsiii- Plateaus

EXOGENITIC FORCES:

Mountains:

A mountain is a large landform that stretches above the surrounding land in a limited area usually in the form

of a peak. A mountain is generally steeper than ahill. The adjective montane is used to describe mountainous

areas and things associated with them. The study of mountains is called Orography. The highest mountain on

Earth based from sea level is Mount Everest (8,848 m (29,029 ft)) in the Himalayas ofAsia. The highest known

mountain in the Solar System is Olympus Mons on the planet Mars at 21,171 m (69,459 ft). Mountains and

mountain ranges on Earth are typically formed by the movement and/or interaction oflithospheric plates.

In the Oxford English Dictionary a mountain is defined as "a natural elevation of the earth surface rising more

or less abruptly from the surrounding level and attaining an altitude which, relatively to the adjacent elevation,

is impressive or notable."

Mountains cover 64% ofAsia, 25% ofEurope, 22% ofSouth America, 17% ofAustralia, and 3% ofAfrica. As

a whole, 24% of the Earth's land mass is mountainous and 10% of people live in mountainous regions. Most of

the world's rivers are fed from mountain sources, and more than half of humanity depends on mountains for

water.

Mountains are made up of earth and rock materials. The outermost layer of the Earth or the Earth's crust is

composed of seven primary plates. When two plates move or collide each other, vast land areas are uplifted,

forming mountains.

Geology

A mountain is usually produced by the movement oflithospheric plates. Compressional forces, isostatic uplift

and intrusion ofigneous matter forces surface rock upward, creating a landform higher than the surrounding

features. The height of the feature makes it either a hill or, if higher and steeper, a mountain. The major

mountains tend to occur in long linear arcs, indicating tectonic plate boundaries and activity. Two types ofmountain are formed in this way depending on how the rock reacts to the tectonic forces,fold mountains or

fault-block mountains. Other mountain building processes include volcanoes and sea floor spreading.

Types

Classified by the geological processes that shape them, there are five major types of mountains:

Fold mountains:
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Fold mountains are the most common type of mountains. They are formed due to collision of two plates,

causing folding of the Earth's crust. Compressional forces in continental collisions may cause the compressed

region to thicken and fold, with material forced both upwards and downwards. Since the less dense continental

crust "floats"on the denser mantle rocks beneath, the weight of any crustal material forced upwardto form hills,

plateaus or mountains must be balanced by the buoyancy force of a much greater volume forced downwardinto

the mantle. Thus the continental crust is normally much thicker under mountains ( sometimes called "mountain

roots"), compared to lower lying areas. However, in many continental collisions (e.g. the Himalayas) part of one

continent may simply override the other, crumpling in the process with the overridden crust forming much ofthe support. Mountains may similarly be partly supported by oceanic crust subducted beneath the continental

crust (e.g. the Andes as the Nazca plate flows beneath the South American Plate). Examples of fold mountains

are the Himalayas of Asia and the Alps in Europe.

Fault-Block mountains:

As the name suggests, fault-block mountains or fault mountains are formed when blocks of rock materials slide

along faults in the Earth's crust. This occurrence is fairly common. The uplifted blocks are block mountains or

horsts. The intervening dropped blocks are termedgraben: these can be small or form extensive rift valley

systems. This form oflandscape can be seen in East Africa, the Vosges, the Basin and Range province ofWestern North America and the Rhine valley. These areas often occur when the regional stress is extensional

and the crust is thinned.

Rock that does not fault may fold, either symmetrically or asymmetrically. The upfolds areanticlinesand the

downfolds aresynclines: in asymmetric folding there may also be recumbent and overturned folds. The Jura

Mountains are an example of folding. Over time, erosion can bring about an inversion of relief: the soft upthrust

rock is worn away so the anticlines are actually lower than the tougher, more compressed rock of the synclines.

There are two types of block mountains, namely the lifted and tilted. Lifted mountains have two steep sides;

whereas, the tilted type has one steep side and a gentle sloping side. Examples of fault-block mountains are

found in the Sierra Nevada mountain range of the western United States.

Volcanic mountains:

Volcanic mountains are formed due to volcanic eruptions where magma piles up on the surface of the Earth.

Examples of volcanoes include Mount Fuji in Japan and Mount Pinatubo in the Philippines. Inactive or extinct

volcanic mountain include Mount Elbrus in Russia, Mount Kinabalu in Malaysia, Cotopaxi in Ecuador and

Aconcagua in Argentina.

Dome mountains:

Dome mountains are formed when the hot magma rises from the mantle and uplifts the overlying sedimentary

layer of the Earth's crust. In the process, the magma is not erupted, but it cools down and forms the core of the

mountain. They are called dome mountains due to their appearance that resembles a dome shape. An example

of a dome mountain is Navajo Mountain in the U.S. state of Utah.

Plateau mountains:

Plateau mountains are formed erosion of an uplifted plateau. Examples of plateau mountains are in the

Adirondack Mountains in the U.S. state of New York.
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Plains:

In geography, a plain is land with relatively low relief, that is flat or gently rolling. Prairies and steppes are

types of plains, and the archetype for a plain is often thought of as a grassland, but plains in their natural state

may also be covered in shrublands, woodland and forest, or vegetation may be absent in the case of sandy or

stony plains in hot deserts. Types offlatlands for which the term is not generally used include those covered

entirely and permanently by swamps, marshes, playas, or ice sheets.

Plains occur as lowlands and at the bottoms ofvalleys but also on plateaus at high elevations. In a valley, a

plain is enclosed on two sides but in other cases a plain may be delineated by a complete or partial ring of hills,

by mountains or cliffs. Where a geological region contains more than one plain, they may be connected by a

pass (sometime termed a gap). Plains may have been formed from flowing lava, deposited by water, ice or

wind, or formed by erosion by these agents from hills. Plains in many areas are important for agriculture

because where the soils were deposited as sediments they may be deep and fertile, and the flatness facilitates

mechanization of crop production; or because they support grasslands which provide good grazing for livestock

Types of terrestrial plains

Coastal plain, an area of low-lying land adjacent to a sea; the term is used especially where they contrastwith hills, mountains or plateau further inland.

Alluvial plains are formed by rivers, and may be one of these overlapping types:o Flood plain, adjacent to a stream, river, lake or wetland that experiences occasional or periodic

flooding.

o Alluvial plain, formed over a long period of time by a river depositing sediment on itsfloodplain or bed which becomes alluvial soil. The difference between a floodplain and an

alluvial plain is that the floodplain represents the area experiencing flooding fairly regularly in

the present or recently, whereas an alluvial plain includes areas where the floodplain is now and

used to be, or areas which only experience flooding a few times a century.

o Scroll plain, a plain through which a river meanders with a very low gradient. Lacustrine plain, a plain that originally formed in a lacustrine environment, that is, as the bed of a lake. Lava plain, formed by sheets of flowing lava. Glacial plains are formed by the movement of glaciers under the force of gravity:

o Till plain, a plain ofglacial till that forms when a sheet ofice becomes detached from the mainbody of a glacier and melts in place depositing the sediments it carries. Till plains are composed

of unsorted material (till) of all sizes.

o Sandur (plural sandar), a glacial out-wash plain formed of sediments deposited by melt-water atthe terminus of a glacier. Sandar consist mainly of stratified (layered and sorted) gravel and sand
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Plateau:

In geology and earth science, a plateau, also called a high plain or tableland, is an area ofhighland, usually

consisting of relatively flat terrain.

Formation

Plateaus can be formed by a number of processes, including upwelling ofvolcanicmagma, extrusion oflava,

and erosion by water and glaciers. Magma rises from the mantle causing the ground to swell upward, in thisway large, flat areas of rock are uplifted. Plateaus can also be built up by lava spreading outward from cracks

and weak areas in the crust. Plateaus can also be formed by the erosional processes ofglaciers on mountain

ranges, leaving them sitting between the mountain ranges. Water can also erode mountains and other landforms

down into plateaus.

Classification

Plateaus are classified according to their surrounding environment.

Intermontane plateaus are the highest in the world, bordered by mountains. The Tibetan Plateau is onesuch plateau.

Piedmont plateaus are bordered on one side by mountains and on the other by a plain or sea. Continental plateaus are bordered on all sides by the plains or seas, forming away from mountains. Volcanic plateaus are produced by volcanic activity. The Columbia Plateau in the northwestern United

States of America is one such plateau.

Dissected plateaus are highly eroded plateaus cut by rivers and broken by deep narrow valleys.

Major plateaus of the world

The largest and highest plateau in the world is the Tibetan Plateau, called the "roof of the world", which is still

being formed by the collisions of the Indo-Australian and Eurasiantectonic plates. In all, the Tibetan plateau

covers an area of some 2.5 million square kilometres, approximately 5000 m above sea level.

The second-largest current plateau in the world is the Antarctic Plateau, which covers most of the central part of

Antarctica. In that region of Antarctica, there are no mountains that we know of, but rather 3000 meters or more

of ice - which very slowly spreads toward its coastline via enormous glaciers.

The third-largest plateau in the world is probably the one in South America that lies in the middle of the Andes

Mountains. This Andean Plateau covers most ofBolivia, central Ecuador, central Peru, northern Chile andnorthern Argentina.

Major plateaus of North America

In North America, the largest plateau is the Colorado Plateau covering an area of about 337,000 square

kilometres (130,000 sq mi) in Colorado, Utah, Arizona and New Mexico.
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Weathering

the set of exogenic (physical, chemical and biological) processes that alter the physical and chemicalstate of rocks at or near the earth's surface

intensity of most weathering decreases with depth, because variations in temperature and moisturesdecrease with depth

therefore biochemical weathering is generally confined to the uppermost few metres of soil and rock occurs in situ (nontransported alteration), unlike erosion which removes soil and weathered rock;

although the 2 sets of processes proceed simultaneously with positive feedback

the 2 forms of weathering act simultaneously and affect the nature and rate of one another: disintegrationproduces an increase in rock surface area while changes in strength with changes in composition

Functions of weathering

1. gives rock lower strength and greater permeability, rendering it more susceptible to mass wasting anderosion; reduces strength (cohesion and friction) and increases permeability of rock and therefore

decreases resistance to fluid and gravitational stresses; precursor to erosion

2. produces minor landforms, produces landforms in soluble rock (especially limestone) and otherwisecreates microrelief (e.g. weathering pits)

3. releases minerals in solution (e.g. iron oxides, silica, carbonates) which become concentrated to formhard coatings on rocks and hard resistant layers in soil (duricrusts) that inhibit seepage and resist erosion

4. first step in soil formation; ultimately produces an unconsolidated mass of 1) minerals that resistedalteration (e.g. feldspar), 2) new minerals (e.g. bauxite), 3) organic debris

Physical weathering

physical weathering is the disintegration of rock and soil aggregates, by physical (mechanical) processesacting primarily on pre-existing fractures (e.g. joints, cracks between mineral grains); reduces size of

fragments according to rock and soil structure (producing grains, crystals, blocks, slabs, etc.), with no

change in composition and

Processes

1. stress (pressure) release: disintegration of rock in parallel sheets as it expands in response to the removalof confining stress

o most common mechanism of stress release is removal of overlying rock by erosion; thus thisprocess is controlled by erosion but subsequently controls erosion


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o the dilation fractures conform to the surface topography and increase in spacing with depth (e.g.from a few cm at the surface to a few metres at 30 m in the Sierra Nevada Mountains of

Yosemite National Park)

o thermal contraction due to cooling counteracts expansion; therefore stress release is mostpronounced near the surface where the rocks have already cooled and contracted

o also most common in massive rocks: higher thermal conductivity causes heat loss and thusreduces counter influence of cooling and contraction, fractured or thinly bedded rock will expand

with out sheeting, massive rocks store stress until overburden pressure is very low (i.e. about 100

m of overburden)

o stress release causes exfoliation: the separation of concentric layers of rock

2. thermal expansion and contraction (insolation weathering)o the surface temperature of dark colored rock can vary from 0-50o C between day and night, since

rock (esp. jointed rock) has low thermal conductivity

o the differential stresses of expansion and contraction of the outer 1-5 cm of rock causesseparation of concentric shallow layers (another form of exfoliation) called spalling or spheroidal

weathering when it effects boulders

o controversy about effectiveness re: the ability of solar radiation to generate sufficient heating and cooling rocks disintegrate after fires, especially rocks composed of minerals with varying

coefficients of volumetric expansion (e.g. granite: volume of quarts increases 3X morethan that of feldspar; versus greater resistance of fine-grained rocks)

dry granite heated and cooled from 30 to 140o C for 89,400 cycles over 3 years(equivalent of 244 years of diurnal cycles) produced no perceptible change, even with

microscopic examination (Griggs, D.T. 1936. The factor of fatigue in rock exfoliation. J.

Geol. 44: 783-796)

but, 244 years is small amount of geologic time

3. growth of foreign crystals (salt weathering)o mainly hydrated salts which are water soluble at normal ranges of atmospheric temperature and

humidity; they hydrate and dehydrate repeatedly generating considerable stresses in fractures and

between grain boundaries in permeable rock

o mostly granular disintegration
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o minerals are transported in solution and precipitate as soil and groundwater evaporate; thus mosteffective in desert landscapes where water tables are near the surface

o origin of salt: sea water, chemical weathering of marine or evaporite sediments, dissolved insnow and rain, precipitates in lakes

o e.g. gypsum: relatively insoluble except in acid rain (dilute sulfuric acid), thus enhancedweathering with acid rain

4. hydration (slaking)o wetting, swelling and disintegration of soil aggregates, layered and fine grained rockso also pressure of air drawn into pores under dry conditions and then trapped as water advances

into soil and rock; suction or -ve pore pressure (less than atmospheric) can exert considerable

stress

o e.g. biotite expands 40% by volume contributing to the weathering of graniteExpansion of Clay Minerals by Volume

Ca-montmorillonite 45-185%

Na-montmorillonite (bentonite) 1400-1600%

illite 15-120%

kaolinite 5-60%

5.6. frost shattering and hydration shattering

o freezing of water in pores and fractureso the specific volume (vol./unit mass) of water increases by 9% upon freezing producing stress that

is greater than the tensile strength of all common rocks

o therefore the stress generated by the crystallization of ice is the most pervasive mechanism ofweathering, effects all rocks

o however, the effectiveness of freezing water is influenced by lack of confinement: if more than 20% of pore space is empty, then the tensile stress may

be less than the tensile strength, thus frost shattering is most effective in saturated rock;
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ice under pressure deforms plastically and thus will extrude through daylighted fractures

and pores

decreased freezing point with increasing pressure (supercooled water) and impurities (e.g.salt)

necessary frequency and magnitude: extent of frost shattering is a function of thecombination of frequency, duration and intensity (rapidity and degree) of freeze-thaw

cycles

o hypotheses to account for apparent effectiveness of frost shattering; hydrofracturing: thin (monomolecular) films of water do not freeze even at low temperatures, given strong

capillary adhesion to rock; powerful molecular forces in these thin films of

semicrystalline water draw water along microfractures opening and propagating them

shallow freezing forces films of capillary water along microfractures, disintegrating rockswell below the depth of freezing; e.g. hydrofracturing in the Allegheny Mountains

(southern Appalachians of West Virginia and Pennsylvania) extends to 12-15 m, whilefrozen ground rarely extends below 1 m

7. plantso minor agent of weatheringo maintain cracks created by other processeso roots may pry rocks apart when tall trees sway in a strong wind; root throw can break fragments

away from bedrock

o as lichens expand and contract or are removed by abrasion they can pull small rock fragmentsloose

Chemical Weathering

chemical weathering is the decomposition of soil and rock (change in composition) by biochemicalprocesses

weathering pits form where water collects and accentuates rates of chemical weatheringProcesses

1. oxidationo process by which an element loses an electron to dissolved oxygeno iron is the most commonly oxidized mineral element Fe+2 (ferrous iron)> Fe+3 (ferric iron)

or 2FeO + O2> Fe2O3
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o other readily oxidized mineral elevments include magnesium, sulfur, aluminum and chromiumo among the immediate chemical weathering processeso gives altered earth material a characterisiticyellowish brown to red coloro water table is boundary between oxidizing and reducing environments

2. hydroloysiso decomposition of minerals in water as hydrogen ions replace cations in mineralso pure water is a poor H+ donor, however CO2 dissolves in water to produce carbonic acid:o CO2 + H2O> H2CO3 (carbonic acid)> H+ + HCO3- (bicarbonate)o soil air is greatly enriched in CO2 by decay of humuso up to 30% of soil air is CO2 as compared to 0.03% of the atmosphereo biogenic CO2 is the major source of carbonated groundwatero solubility of CO2 increases as water temperature decreases (warm beer is flat)o hydrolysis is the most important process in the weathering of silicate mineralso the most common weathering reaction on earth is the hydrolysis of feldspars producing clay

minerals

o e.g. K-feldspar>kaolinteo 2KAlSi3O8 + 2H2CO3 + 9H2O> Al2Si2O5(OH)4 + 4H4SiO4 + 2K+ + 2HCO3-o the other weathering products (silicic acid and ions) are in solution, so the residue is clayo the soil water solution becomes more basic as H+ is consumed

3. carbonation (solution)o dissolution of calcium carbonate in acidic soil and groundwatero CaCO3 + H2CO3> Ca+2 + 2HCO3-o similar reaction as hydrolosis but the dissolution is congruent, that is, the products are ionic,

there is no residue

o bicarbonate represents the largest constituent of the dissolved load of most riverso carbonation of limesotone results in karst topographyo the insoluble minerals form soil
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4. cation exchangeo substitution of mineral cations in solution for those held by mineral grains and crystalso changes spacing in crystal lattice but not molecular structureo

most effective in clay-textured sediments as cations adhere to the surface of negatively chargedclay minerals

o organic matter and sodium zeolites (watertsoftner salt) have a high cation exchange capacity(CEC)

o CEC = f(temperature, content and chemistry of interstitial water, types and abundance of ions)o colloidal suspensions of clay and organic matter adsorb H+ creating acidic soil and weathering

environment

5. chelationo minerals cations incorporated into hydrocarbon molecules (complexing agents or chelates)o chelating agents are produced by alteration of humus in plant acids and excreted by lichenso e.g. ethylenediaminetetracedic acid (EDTA) is a common food additiveo chelates in solution are stable at pH under which the incorporated cation would normally

precicpitate and thus they are leached in seeping soil water

o H+ released during chelation from organic molecules is available for hydrolysiso thus plants contribute to the decomposition of soil and rock waste at depths to the base of the

root zone

o lab experiments with equisetum (horse tail) in crushed rock show silica uptake equivalent toremoving the silica form 30 cm of basalt in 5350 years

o the dissolved load of runoff from barren basalt plateaus in Iceland suggest that the rate ofweathering is 1/3 as fast as on lichen covered surfaces

Climate and weathering

weathering is an exogenic geomorphic process, i.e. climatically-controlled it is controlled by moisture, temperature and seasonality, the same parameters that define regional

climates

in tropical climates, high temperatures, large annual rainfall and continuous biological activity maintainhigh rates of chemical weathering


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water is the agent of all weatering, except stress release (although water erosion is a mechanism ofunloading of rock)

all chemical weathering occurs in solution

MASS WASTING PROCESSES AND LANDFORMS

mass wasting

gravitational movements of earth materials especially unconsolidated sediments and weathered rock water contributes to reduced strength of materials but is not involved as a geomorphic agent transitional between weathering and erosion, because it is closely related to the declining strength of

weathering earth materials, but does not involve a transporting medium ( e.g. water, wind, ice)

colluvium

earth materials moved by gravity

gravitation

tendency for matter at the earth's surface to accelerate towards the center of the earth, given the smallmass relative to the earth

gives all mass above the earth's surface potential energyo PE = mgho acceleration due to gravity (g) is constant (9.8 m sec -2)o therefore, for a unit mass PE is proportional to height or reliefo slope gradient (h/d) is also an energy gradient governing the rate of conversion from potential to

kinetic (1/2mv2) energy

o high geopotential energy is available for mass wasting in landscapes with large relief (h) andsteep slope (h/d)

mass moves over hillslopes when the shear stress exceeds the resistance to shearing (shear strength)Mass Wasting Processes

Classification

type of material: rock, sediment, ice, snow, mud, sand amount of ice or water involved morphology of resulting landform: lobes, levees, talus, slump blocks type of movement (mechanism) is the most common and unambiguous criterion:1. spread (creep)

o slow, imperceptible, seasonal decline in shear strengtho decreasing velocity with deptho soil creep: slow spread as soil expands and contracts with freezing and thawing or wetting and

drying

o rock creep: slow continuous failure of rock masses, especially in rocks with low yield stress andoverlain by stronger rocks; often the precursor to rapid catastrophic mass movements

2. flowo rapid failure of earth materials by internal shearing (liquid behavior)
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o usually related to excessive porewater pressureo earthflow: flow of unconsolidated materials on an open slope

Mink Creek Earthflow, Terrace, B.C.o debris flow: confined fluid mass wasting, i.e. in a stream channel, but moving independent of the

stream

o debris flow fans form at the mouths of steep canyons3. slide

o slope failure as rock(rockslide) or less consolidated earth materials (landslide) fail at depth byshearing along a distinct sliding plane

o rotational landslide (slump): curved sliding surfaceo translational landslide: planar sliding surface

4. fallo the free fall, bouncing and rolling of rock (rockfall) over steep weathering cliffs to from talus

composite failures

many movements of earth materials involve a combination of processeso rock avalanche: rapid mass wasting of rock, ice and snow involving sliding and fallingo solifluction: spread and flow of saturated substrate over an impermeable stratum (e.g.gelifluction

over permafrost )

o landslide is the term most commonly used to refer to mass wasting events, even though slidingmay be only one (often the initial) mode of failure
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Endogenic and Exogenic Forces:

The processes that shape landforms can be categorized as endogenetic or exogenetic.

Endogenetic processes are related to plate tectonics and to the surface effects of plate movements, horizontally

and vertically, as well as to other processes originating from the Earth's interior.

Exogenetic processes develop at or above the surface in the atmosphere, hydrosphere, cryosphere, or biosphere.

They involve wind, water, ice, mass movements, or living organisms that modify landforms. Impact andaccumulation of extra-terrestrial materials (meteorites, comets, etc.) are also exogenetic processes.

Endogenetic and exogenetic processes combine with structure and time to produce the observed landforms atthe Earth's surface. Most landforms involve a considerable mass of material--bedrock and sediment, and so are

slow to adapt when environmental changes take place. The geomorphology of a region, therefore, represents a

long-term integration of environmental conditions and trends. A region's geomorphology is, thus, a reflection of

both past and present environments.

Documents

Weathering Geo