earth movements tch r

8/11/2019 Earth Movements Tch r

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Te%c&in( )*e%rnin( m%teri%*# %n" %cti+itie#.

#e't +oos -iagrams sho$ing the different features and formation of different pro"esses.

SU-TO,IC: FOLDING AND FAULTING.

Intro"uction:

#he for"es $hi"h produ"e physi"al features are of t$o folds i.e. internal for"es and

e'ternal for"es.,nternal for"es are lateral and verti"al for"es $ithin the earth surfa"e leading to

earthuaes& vul"ani"ity& faulting and folding.

E'ternal for"es operates on the earths surfa"e leading to denudation & gla"iation river

a"tion and $ave a"tion.

Earth movements have led to the formation of features on the lands"ape of East

%fri"a. /a0or features su"h as mountains plateaus& plains& rift valley.

#he movements are lateral and verti"al and e'ert great for"es of tension and

"ompression& though tae pla"e very slo$ly they eventually produ"e impressive

features.

rie! "e#cription o! t&e #ubtopic:

#his su+topi" des"ri+es the t$o pro"esses of folding and faulting &the features

produ"ed and their importan"e to human a"tivities.

$%in content %n" concept# to emp&%#i'e.

#he tea"her should emphasise the follo$ing $hen tea"hing:

-efinitions of the follo$ing terms.

a) Earth movements.

+) Sedimentary ro"s.

") Stratified ro"s

d) #ension and "ompression for"es.

e) Folding


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f) Faulting

g) Earth uaes.

-es"ri+e tension and "ompression for"es.

-es"ri+e the nature of folds.

,dentify the features formed as a result of folding.

,dentify the types of faults.

E'plain the features formed as a result of faulting.

E'plain the origin of the rift valley using the theory of tension and "ompression

theory.

,dentify the importan"e of faulting and folding on human a"tivities in East %fri"a.

Te%c&er# (ui"e.

2earning o+0e"tives:

Students should +e a+le:

#o define $hat faulting and folding is& earth movements& sedimentary

ro"s et".

#o des"ri+e the different pro"esses under earth movements.

#o identify the features produ"ed as a result of faulting and folding.

,dentify the importan"e of folding and faulting to human a"tivities.

Re!erence#:

1) .* *unnett (1) General Geography in -iagrams& 3rdEdition& 2ondon&

metro forms and system ltd.

) o+ert 6aruggah and 7udith 6a+asi (13) 8ertifi"ate Geography form &

9airo+i 'ford ;niversity orld Geography (East %fri"a


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Topic Note#:

Earth movements "ause sedimentary ro"s to +e displa"ed i.e. to +e pushed out of the

horiAontal plane so that the ro"s are tilted or in"lined.

Earth movements "an also "ause folding and faulting of the sedimentary ro"s.

Folding results from lateral for"es f "ompression.

2ateral for"es of "ompression "ause folding $hile either lateral or verti"al for"es of

tension or "ompression "ause faulting.

T&e proce## o! !o*"in(.

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T&e n%ture o! !o*"#.

#he layers of ro" $hi"h +end up form an up !o*" or %ntic*ine. #hose $hi"h +end

do$n form a "o/n !o*" or #0nc*ine. #he sides of a fold are "alled the *imb#.if

"ompression "ontinues the simple folds are "hanged first to % #0mmetric%* !o*"#& then

into o+er !o*"#and finally into o+er t&ru#t !o*"#.

A #imp*e !o*"

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#he "entre line of the up fold or do$n fold is "alled the a'is. ,n simple folding& the

folding pro"ess is never intense.

#he pro"ess gives rise to mountains and valleys. #he anti"lines +e"ame the mountains

and syn"lines the valleys. #he sides of a fold are "alled the lim+s.

A #0mmetric%* !o*"

ne lim+ steeper than the other

An o+er !o*" or recumbent !o*"

%n over fold is formed $hen one lim+ is pushed over the other lim+. #his pro"ess

o""urs $hen the "ompressional for"es from one side are greater than from the otherside.

B


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An o+er t&ru#t !o*"

>hen pressure is very great a fra"ture o""urs in the fold and one lim+ is pushed

for$ard over the other lim+ forming an overthrust fold.

,n east %fri"a folding did not "ause high mountains as the "rust "onsists of hard

+asement ro"s $hi"h fra"tures $hen folded.

?o$ever minor folds are found in south$estern ;ganda in 6igeAi distrist $here

layers of mudstone $ere "ompressed into a ; shape. #here is also some folding in the

layers of limestone on the East %fri"a "oast. Folding is evident in *ua+a region in

the 9orth of #anAania.

C


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T&e re#u*t# o! !o*"in(

Note:Fold /ountains "an +e found in the 9orth >est %fri"a i.e. %tlas /ountains and

in South %fri"a i.e. 8ape anges.


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FAULTING.

% fault is a +rea& "ra" or a fra"ture in the Earth "rust produ"ed +y verti"al and

lateral movements $ithin the earths "rust.

Faulting is one of the internal land forming pro"esses $hi"h shapes the earths

surfa"e. ,t is "aused +y earth movements& $hi"h "reate for"es of tension and

"ompression that are either lateral or verti"al for"es.

,f for"es of tension and "ompression are "reated +y earth movements the ro"s of the

earth "rust may fra"ture or "ra". thus the faults are formed . #he line along $hi"h

ro"s have fra"tured is "alled a fault.

#ension "auses % norm%* !%u*t& "ompression "auses % re+er#e !%u*tand lateral

movement produ"e % te%r !%u*t.

E#c%rpment# "alled fault s"arps develop if faulting is a""ompanied +y up$ard or

do$n$ard movements of ad0oining parts of the "rust.

T0pe# o! !%u*t#

Norm%* !%u*t#

#hese are formed +y the for"es of tension. ,f the ro"s are under tension& faults $ill +e

formed and the "entre +lo" may sin do$n relative to its neigh+ours.

9ormal faults are "ommon in East %fri"a.


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Re+er#e !%u*t#.

#hese are also no$n as thrust faults and are "aused +y the for"es of "ompression

$hen the strata or layers are "ompressed or pressed together the ro"s $ill "ra" and

faults $ill +e formed. ne +lo" of ro"s may override another to form a +la"

mountain or a horst. Su"h faults are "ommon in $estern ;ganda. #he $enAori

mountain is an e'ample of a +lo" mountain formed +y thrust faults.

Te%r !%u*t.

>hen lateral movement is taing pla"e parti"ularly during an earthuae& tear faults

may o""ur. #ear faults are also no$n as $ren"h or transform faults. ,f a tear fault

o""urs a"ross the "ourse of a river& then the rivers "ourse may +e slightly offset.

1@


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T&e re#u*t# o! !%u*tin(.

FEATURES FOR$ED 1,RODUCED2 AS A RESULT OF FAULTING.

Faulting has produ"ed a variety of physi"al features over the surfa"e of the earth.

%mong the most remara+le features areD

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*lo" mountains

#ilt +lo"s

ift valleys or gra+ens

Es"arpments or fault s"arps

ift laes.

*oc3 $ount%in#.

% +lo" mountain is also no$n as a Hor#t. ,t is formed $hen the middle +lo" of lnd

+ounded +y more or less parallel faults is made to rise or is uplifted +y the

"ompressional for"es. #he +est e'ample of a +lo" mountain in East %fri"a is mount.

$enAori& also no$n as the mountain of the moon thers in"lude /athe$s and

9yiru 9dotos in 9orthern 6enya.

Ti*t *oc3#.

#ilt +lo"s are formed $hen one side of the middle +lo" is uplifted higher than the

other side. #he top of the middle +lo" $ill not +e flat +ut $ill +e tilted. E.g. $est

6enya tilt +lo"& $hi"h rises to a+out 1@@ metres to$ards lae !i"toria.

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E#c%rpment#.

Es"arpments are also no$n as fault s"arps. #hey are steep "lifflie slopes.

Es"arpments are said to have +een formed during the formation of the rift valleys.

Some es"arpments are steep and may e'tend several hundred ilometres. E'amples of

su"h es"arpments in East %fri"a in"lude:

/andi(6enya)

*utia+a (uganda)

Eldeyo mara$et (6enya)

6iuyu (6enya) /au (enya)

2ae manyara (#anAania)

9yendo (6enya)

6eiyo (6enya)

9yandarua (or %+erdare) (6anya)

8huya (#anAania.)

RIFT 4ALLE5S

% rift valley is an elongated trough +ound +y t$o infa"ing es"arpments.

ift valleys are long& narro$ depressions on the earth surfa"e +ounded +y more or less

parallel faults. % rift valley is also no$n as % (r%ben.

ift valleys are thought to have +een developed either from the a"tion of tensional

for"es in the "rust or from the a"tion of "ompressional for"es.

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#he East %fri"a rift valley system e'tends south$ards from the ed sea& through

Ethiopia and East %fri"a to /ala$i.

#he east %fri"a rift valley "overs a distan"e of appro'imately 5&B@@m .it is divided

into t$o +ran"hes that is& the $estern rift valley and the eastern rift valley.

#he >estern +ran"h stret"hes from lae %l+ert in ;ganda to lae /ala$i. #he eastern

+ran"h stret"hes from lae #urana in northern 6enya to lae /ala$i.

#he $idth of the rift valley varies from pla"e to pla"e. #he average $idth is +et$een

5@m and B@m.

n the floor of the rift valley there are a num+er of rift laes and vol"ani" "raters su"h

as longonat "rater and menengai "raters.

Ori(in o! t&e ri!t +%**e0#.

% num+er of theories have +een put for$ard to e'plain the origins of rift valleys.

?o$ever& only t$o have remained popular thus the t$o theories $hi"h attempt to

e'plain the origin of rift valleys. ne relies on the for"es of tension and the other on

the for"es of "ompression. *oth theories depend on up$ard s$ells& along the sides of

$hi"h faults develop.

T&eor0 : Ten#ion !orce#

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a) #ension for"es a"t on the layers of ro".

+) Gradually t$o parallel faults appear and the "entral +lo" +egins to su+side

(sin).

") 2and in +et$een sins in forming a rift valley. #he land on either sides stays in

pla"e.

%fter su+siden"e a depression $ith steep fault s"arp sides i.e. a rift valley is formed. ,t

is trapped in position +y later pressure.

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a)

+)

")


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T&eor0 6: Compre##ion%* !orce#

a) 2ayers of ro"s are su+0e"ted to "ompression for"es.

+) Faults develop and the outer +lo"s move up$ards. everse faults are formed.

") 8entral +lo" stays in pla"e and a rift valley is formed.

1B

a)

+)

")


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RIFT 4ALLE5 LA7ES

#hese have +een formed on the floor of the rift valley and they vary in siAe& depth and

salinity. E'amples of the salty laes are 2ae 9atron& and 2ae /agadi. #he rift

valley has several in land $ater +asins $hi"h "ontain laes.

Ri!t +%**e0 *%3e# o! E%#t A!ric%

7en0% U(%n"% T%n'%ni%

2. #urana 2. %l+ert 2.#anganyia

2.*aringo 2.Ed$ard 2.u$a

2.9auru 2.George. .2.9atron

2.Elmentata 2.Eyasi

2.9airasha 2./anyara.

2./agadi

F%;2#E- %E%S ,9 E%S# %F,8%.

#here are faulted areas in east %fri"a outside the rift valley su"h as:

6anrondo rift at 6isumu.

9orthern fa"e of $hi"h is the 9andi s"arp

;sam+ara mountains have fault s"arps.

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A m%p o! E%#t A!ric% #&o/in( t&e e8tent o! t&e Ri!t 4%**e0.

Import%nce o! !%u*tin(.

Faulting has resulted into the formation of high mountains in East

%fri"a. For e'ample the $enAori in $estern ;ganda& the southern

highlands and the ;sam+ara mountains in #anAania and the "entral

highlands in 6enya. #hese are the most produ"tive areas& $here +oth

"ash "rops and su+sisten"e "rops are gro$n.

#hese highlands have a+undant and relia+le rainfall.

ift valley laes for e'ample 2.#anganyia& lae #urana& lae

9aivasha and lae *aringo are fished.

Some of these laes have fresh $ater $hi"h "an +e used for irrigation

and also for domesti" purposes and industrial use.

2./agadi "ontains vast deposits of soda ash& $hi"h is one of the most

important minerals in 6enya.

Faulting presents an impressive s"enery $hi"h "an +e used for tourism

attra"tion. For e'ample 2.9auru has millions of "olourful flamingos

and other +irds.

Some highlands have +een made into 9ational pars and game

reserves e.g. the slopes of the 9yandarua and $enAori mountains .

these pars attra"t many tourists.

Faulting "an also "ause the formatiom of $aterfalls su"h as the

6aruma falls& /ur"hison falls .

Et".

,rob*em# c%u#e" b0 !%u*tin(.

Es"arpments and mountains hinder transport development.

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ift valleys are very hot and only suita+le for graAing +e"ause they are

in the rain shado$ unless irrigation is pra"tised as $ith the "ase of

mo+uu.

#here is severe soil erosion and mass $asting $hi"h result in the

destru"tion of soil surfa"e& "rops and at times peoples property.

,t is diffi"ult to settle on the steep areas $ithin the rift valley and

es"arpments. Et".

In!*uence o! Fo*" $ount%in# on &um%n %cti+itie#.

1. Fold /ountains often re"eive heavy rain or heavy sno$ falls $hi"h may give

rise to important rivers. For e'ample the %lps in Europe.

NB:#he pro"ess of folding $as not signifi"ant in East %fri"a and therefore didnt

"reate any signifi"ant land forms.

ADDITIONAL NOTES.

1. Earth movementsD these are movements $hi"h are lateral and verti"al& they

e'ert great for"es of tension and "ompression and although they usually tae

pla"e very slo$ly they eventually produ"e very impressive features.

. Sedimentary ro"s are formed from sediments& $hi"h have +een laid do$n in

horiAontal layers.

3. Stratifi"ation is the layering of sedimentary ro"s and therefore sedimentary

ro"s are therefore stratified ro"s.

o"s of the earth "rust are su+0e"ted to tension and "ompression $hen verti"al or

lateral earth movements tae pla"e. ,f one part of the earth "rust is "ompressed then

"learly another part must +e stret"hed i.e. under #ension.

o"s under "ompression they may fold or fault depending on $hether they are +rittle

or fle'i+le under stress.

ene!it# o! t&e Ri!t +%**e0 to t&e peop*e o! E%#t A!ric%.

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1. #he +eautiful s"enery attra"ts tourists.

. 2aes in the ift valley provide fish. E.g. 2. #anganyia and 2. %l+ert

3 ift valley laes provide $ater for domesti" and agri"ultural use.

4. 2aes help in navigation ($ater transport)

5. #here is forestry on the slopes& so sour"e of tim+er.

B. Gentle slopes are used for "rop farming and settlement due to fertile soils.

C. ift valley laes are used for mining. E.g. Soda ash from 2.magadi

. /odifi"ation of "limate due to the ?ighlands.

. %reas o little rainfall (rain shado$) provides pasture for graAing.

1@. Study purposes or resear"h.

11. >ildlife "onservation. For e'ample game pars in rift valley areas

Et".

,rob*em# !%ce" b0 t&e peop*e *i+in( in t&e Ri!t +%**e0 %re%# o! E%#t A!ric%

1. Earthuaes (tremors) $hi"h destroy property

. 2ittle rainfall or drought in the ain shado$ areas.

3.


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Acti+it0 6.

1. >hi"h one of the follo$ing laes is not a ift valley lae

%. 2ae 9auru.

*. 2ae 9atron.

8. 2ae !i"toria.

-. 2ae #anganyia.

. #he feature formed $hen a +lo" of the earths "rust is depresses +et$een parallel

faults a:

%. *lo" /ountain.

*. ?anging valley.

8. #ilt +lo"

-. ift valley.

3. %n up thrust +lo" +et$een t$o faults is no$n as:

%. %n es"arpment.

*. % horst

8. % ift valley

-. % vol"ano.

4. >hi"h of the follo$ing mountains in East %fri"a $as formed +y faulting

%. 6iliman0aro

*. 6enya

8. ;sam+ara

-. 2ongonot.

5. >hi"h of the follo$ing mineral is e'tra"ted from 2. /agadi in 6enya

%. o" salt

*. Soda ash

8. Gold

-. -iamond.

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B. #he +eautiful s"eni" landforms of East %fri"a $ere formed as a result of:

%. Folding& faulting and vol"ani"ity a"tivity.

*. Folding& $arping and soil erosion.

8. >arping and tilting.

-. Folding and $eathering.

C. >hi"h of the follo$ing "hara"teristi"s are true of most of the East %fri"a ift

valley laes.

%. >ide& shallo$ and salty

*. 2ong narro$ and shallo$.

8. >ide& deep& and salty.

-. 2ong& narro$ and deep.

. #he follo$ing are vol"ani" mountains e'"ept.

%. 6enya and longnat.

*. 9apa and moroto.

8. $enAori& ;sam+ara

-. 6ilima0aro &/ufum+ira.

. >hi"h of the follo$ing mountains is a +lo" mountain.

%. 6iliman0aro

*. $enAori

8. 6enya

-. /ufum+ira.

1@. >hi"h of the follo$ing laes $as not formed as a result of faulting.

%. 2.magadi

*. 2./anyara

8. 2.mtanda

-. 2./ala$i.

11. >hi"h of the follo$ing laes in a rift valley $ith fresh $ater

%. 9atron

*. 9aivasha


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8. #urana

-. *aringa.

1. >hi"h of the follo$ing types of ro"s is formed in Strata

%. /etamorphi"

*. Sedimentary ro"s

8. ,gneous ro"s

-. %ll a+yssal ro"s.

13. #he +asement ro" of East %fri"a is

%. ?ard

*. Saft

8. ?ighly $eathered

-. 2ight "oloured.

An#/er#:

1. 8 B. % 11. 8

. - C. - 1. *

3. * . 8 13. %.

4. 8. . *

5. *. 1@. 8

Acti+it0 .9

1.a). -ra$ a set"h map of East %fri"a and on it mar and name:

1i2 t$o "omposite "ones

1ii2 one ash vol"ano

1iii2 t$o lava plains

1i+2 the East %fri"an ift valley.

1+2 /ountains: $enAori and ;sam+ara.

1+i2 2.9aivasha and u$a.

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+). -es"ri+e the pro"esses $hi"h led to the formation of "omposite vol"anoes

("ones)

"). E'plain t$o influen"es of vul"ani"ity on:

(i) 8limate.

(ii) %gri"ulture in East %fri"a.

. a) utline any 5 $ays in $hi"h vol"ani"ity is important to the people of East

%fri"a.

+). -es"ri+e one pro"ess $hi"h $as responsi+le for the formation of East %fri"a an

ift valley.

3. a) E'plain five +enefits of the ift valley to the people of East %fri"a.

+) utline five pro+lems fa"ed +y the people living in the rift valley area of East

%fri"a.

4. n the outline map of East %fri"a provided a+ove. /ar and name the follo$ing

features:

(i) #he East %fri"a rift valley.

(ii) 2aes9auru& /anyara& George&9atron

(iii) /ountains ;sam+ara& $enAori& %+erdares& /ufum+ira.

(iv) iversuvuma and %thi.

5. a) -ra$ the map of East %fri"a and sho$

(i) #he rift valley.

(ii) % +lo" mountain

(iii) 2aes: Eyasi& /anyara & 9atron and u$a.

(iv) #o$ns: 7in0a and /om+asa.

+) E'plain ho$ the rift valley $as formed using the tensional theory.

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") ,dentify the pro+lems "aused +y faulting.

An#/er# to Acti+it0. 9

1 (a) % set"h map of East %fri"a sho$ing physi"al features.

8omposite "ones: 1muhavura& 6iliman0aro& 3meru& 46enya.

%sh vol"ano e.g. /t Elgon

2ava plains: %isoro& *ano plains& 8yatta plateau& -*asin Gishu


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(ii) %gri"ulture.


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everse faults develop and divide the ro"s into 3 +lo"s a& +& ".

*lo"s a and " on the outside +egin to thrust up over "entre +lo" +.

#he overhanging sides are $orn +a" +y erosion and the depression

remaining the rift valley.

9. 1%2 Five +enefits of the rift valley to the people of East %fri"a:

#ourist attra"tion i.e. +eautiful s"enery e.g. laes& mountains&

es"arpments et".

2aes in the rift valley provide fish.

2aes in the rift valley provide $ater for domesti" and industrial use

and irrigation for agri"ulture.

ain shado$ areas Jareas $ith lo$ rainfall provide pasture for graAing.

2aes are used for navigation.

#here is forestry on the slopes& so sour"e of tim+er.

Gentle slopes are used for ara+le farming and settlement.

>ildlife "onservation

Salt$ater laes are used for mining.


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1. a) >hat is a fault and ho$ is it formed

+) ?o$ is a rift valley formed

. a) 9ame t$o hand forms "ommon in East %fri"a formed +y the faulting pro"ess.

+) #hrough $hi"h "ountries does the rift valley of eastern %fri"a pass

3. -ra$ diagrams to sho$ the follo$ing features.

+. 9ormal fault

". #ear fault

d. everse fault

4. -ra$ diagrams to illustrate the follo$ing features.

(i) Simple fold

(ii) an overfold

(iii) a symentri"al fold.

5. State three advantages and t$o disadvantages asso"iated $ith the formation of fold

mountains.

SU-TO,IC 6: 4ULCANICIT5.

rie! "e#cription o! #ub ; topic.

#his su+ topi" des"ri+es the pro"esses of !ul"ani"ity& the features produ"ed and their

importan"e to the people.

$%in content %n" concept# to emp&%#i#e.

-efinition of the follo$ing ey $ords:

!ul"ani"ity&

E'trusive features

,ntrusive feature.

#he types of lavaJvol"anoes

Formation of vol"ani" features i.e. !ol"ani" "ones& "alderaJ"rater& *atholith& dyes

sills et"


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Te%c&er# (ui"e

2earning o+0e"tives.

Students should +e a+le to:

-es"ri+e vul"ani"ity as a pro"ess of earth movement.

,dentify the feature produ"ed as a result of vul"ani"ity.

E'plain the advantages and disadvantages of vul"ani"ity.

TO,IC NOTES.


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T0pe# o! intru#i+e !e%ture#

E8tru#i+e !e%ture#.

1. L%+%K that moves to the surfa"e differs in "hemi"al "omposition& this party e'plain

the different types or shapes of vol"anoes and nature of eruption $hether

e'plosions or uite.

%"idi" lava K very thi"& traps a lot of gas & $ater& ri"h in sili"a "ontent violent

eruption and lava solidifies very ui"ly +uilds up steep "ones.

*asi" lava K this is a form of fluid poor in sili"a "ontent flo$s for a very distan"e

+efore it solidifies& it +uilds up gently sloping "ones& lava plateau and

plains.


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. 4o*c%noe#K these are hills or mountains formed $hen magma erupt and piles up

around the vent until a "one is formed. #hese are +asi"ally four types of vol"ani"

"ones.

A#&)cin"er coneK #hese are small +ut steep sided hills formed $hen e'plosive

eruptions thro$ lava high into the air& +reaing up lava into small fragments or pie"es

no$n as pyro"lasti"s (fire ro"s). #he erupted materials +uild up or a""umulate

around the opening no$n as ventD layer after layer forming steep sided "ones of

a+out 15@ metres high. e'amples in 6enya are Sus$a and /enegai hills and #elei

hills south of 2ae #urana and 2ongonat. #he hills are "hara"terised +y a large "rater

J"aldera at the top +e"ause of violet eruptions.

Cr%ter "ir"ular depression c%*"er%K an enlargement of a "rater on top of

at top of vol"ano. mountain as a result of violent eruption.

E'amples are found on menegai& sus$a& longnot in 6enya&

9apaa& and elgon in ;ganda.

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9garogero in #anAania.

#here are also lo$ land e'plosion "raters.e'plosion "raters are flat floor depressions

formed $hen e'plosions eruptions of gases +lo$ off the ro"s at the surfa"e leaving a

shallo$ "ir"ular depression& depressions are filled $ith $ater to form e'plosion "rater

laes. E'amples areD 2. at$e& 2. 9yamurua& 2. /unyanyang& 2. Saa& and 6yegere

and others. Found in $estern ;ganda& in asese & 6a+arole and *ushenyi distri"ts.

%#ic *%+% cone)#&ie*" +o*c%no. #his is a hill $ith gently slopping sides. ,ts formed

$hen hot fluid lava& $ith lo$ sili"a "ontent& flo$s from one or t$o faults in a uiet

eruption. ,t spreads out in flat layers. #he layers +uild up a +road vol"ano $ith gently

sloping sides& shaped lie a shield and hen"e the name shield vol"ano. ,ts "ommon in

;ganda $anda +oarder along the 9yamulagira ranges.

Aci" *%+% "ome: these are doom shaped hills& thi" lava ri"h in sili"a "ontent&

solidifies ui"ly on rea"hing the surfa"e& forming a vol"ani" dome or "one of vis"ous

lava& e'amples K #ern%* +o*c%nodomes in #savo national par in 6enya.

4o*c%nic p*u(

#he thi" lava (vis"ous) lava& at times solidifies in the vent& after prolonged erosion&

the plug is e'posed to the MMM.e'amples are the #ororo ro"s in Eastern ;ganda.

A compo#ite cone:

% "omposite "ones are large mountains formed $hen vol"ani" eruptions alternate

+et$een uite and violent eruptions. %n e'posure period releases gas and ash and

"inder layers. #hen the eruption "hanges to a uite period erupting lava over the top of

ash layer& $hen the "y"le of ash and lave is repeated over and over in alternating

layers& a "omposite vol"ano is formed.

%t times lava is diverted side $ays from the vent forming dyes& 8orre"ts or parasite

"one.E'amples are /t.6enya& 6ilima0aro in #anAania& /aham+ura in South $est

;ganda.

L%+% p*%te%uK formed as a result of uite eruptions& $hen lava moves out slo$ly

along "ra"s Jfaults .the lava fluid lava flo$s for a very long times on the plateau

+efore it solidifies& forming lava plateau.

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E'amples areD 6isoro lava plain in ;ganda& =atta& 2aiipia and #urana plateau in

6enya.

Hot #prin(# )(e0#er

#hese are features produ"ed $hen heated $ater in vol"ani" areas flo$ out ueitely in

form of hot springs or erupt periodi"ally shooting out $ater Jsteam in the air.

E'amples K 6atagata in *ushenyi.

Sempaya in fortportal

/a0imoto in #anAania.

/a0iyamot in 6enya.

L%+% "%mme" *%3e# these are formed $hen lava +lo"s "hannels. >ater pools

+ehind leading to formation of laes. E'amples 2.*unyonyi and 2. /utande in

south$est ;ganda.

Intru#i+e !e%ture#:these are formed $hen magma solidifies underground. /agma

forms in many different shapes and siAes& the most "ommon are:

1. %t&o*it: these are mostly massive ro"s. #hey are dome shaped& formed at great

depth and at times they are e'posed at the surfa"e +y denudational for"es as

insel+ergs. E'amples are mum+ende hills& para+ong and la+$a hills in %"holi.

/umias and 6isii +atholith in 6enya.

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. D03e#: formed $hen magma solidifies into verti"al "ra"s& "utting a"ross ro"

layers. >hen affe"ted +y erosion dyes may stand as a ridge. #here are ridges in most

of #urana and Suulu hills South of #ororo to$n.

3. Si**#: formed $hen lava solidifies in +et$een ro" layers& after prolonged erosion&

Sills may +e e'posed as es"arpments and $hile they o""ur a"ross a river valley they

"ause $ater falls and rapids. E'amples are #hia and #hompson falls in 6enya&

6aruma falls and *u0agali in ;ganda.

4. L%cco*it&: this is magma $hi"h solidifies in a shape similar to a mushroom. %fter

prolonged erosion& it may form upland.

5. L%ppo*it&: this is a sau"e shaped magma& after erosion. ,t "an +e e'posed as a

shallo$ +asin. E'amples are %renas in %nole.

A"+%nt%(e# o! 4u*c%nicit0.

1. !ol"ani" mountains and lava plateau provide fertile vol"ani" soils $hi"h support

agri"ulture& e.g. %ra+i" "offee is gro$n on mountain Elgon& /ufum+iro& 6enya and

6iliman0aro& "offee earns the "ountry foreign "urren"y and provides employment&

other "rops gro$n in"lude $heat& tea& pyrethrum& maiAe& +ananas& vegeta+les& irish

potatoes.

. #he highland areas are densely settled. #his is due to the fertile soils and "ool

"limate& e.g. *ugishu& 6igeAi& 6enya and 6iliman0aro highlands. ,n addition some of

these areas have large to$ns lie 6a+ale& /+ale& /oshi& and 9airo+i. #his has led to

development of "ommer"ial a"tivities.

3. #he vol"ani" features espe"ially mountains are tourist attra"tions. #hey provide

sporting a"tivities lie mountain "lim+ing. #hey generate in"ome in form of foreign

e'"hange and provide employment to lo"al people.

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4. !ol"ani" mountains influen"e "limate& lead to formation of geographi" or relief

rainfall $hi"h is important for agri"ulture. Some mountains are i"e "apped. #hey are a

sour"e of many rivers& $hi"h provide $ater for domesti" use and generate

hydroele"tri" po$er.

5. #here are forest reserves on the slopes of mountains lie Elgon& /ufum+iro 6enya&

and 6iliman0aro $hi"h are valua+le sour"e of tim+er and fire$ood. #he forests also

a"t as $ildlife "onservation areas e.g. *$indi impenetra+le forests& has the largest

population of gorillas& $hi"h promote tourism.

B. 2ava or magma is ri"h in minerals e.g. #ororo ro" vol"ani" plug is a sour"e of

limestone for the "ement industry. ,ron&tin uranium are found in the /ufum+iro

ranges.

2ae 6at$e $hi"h is an e'plosion "rater is a "entre for salt mining. #he 6im+erlite

ro" in #anAania is "entre for gold mining. /inerals provide revenue and

employment.

C. ?ot springs or Geysers are potential sour"e of Geothermal po$er (ele"tri"ity).in

6enya &the laria Geothermal


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1. !ol"ani" features espe"ially mountains are "ommuni"ation +arriers due to

steepness.

. ,t is very e'pensive and risy to "onstru"t roads and rail$ays in the hilly areas.

3. !ol"ani" eruption leads to loss of lives and property.

4. ?eavy rainfall and steepness lead to soil erosion& mass $asting and landslides

$hi"h are "ommon in 6igeAi and Elgon areas.

5. /ountains a"t as +arriers to rainfall espe"ially on the lee$ard side (rain shado$

areas) this "auses aridity.

B. ,ntrusive features lie sills and dyes form $aterfalls and rapids $hi"h hinder

navigation of rivers.

C. >here there are ,nsel+ergs and *atholiths mae agri"ulture pra"tising diffi"ult.

Acti+it0 .=

1. a) -efine !ol"ani"ity.

+) 9ame the e'trusive features of !ol"ani"ity.

. a) -ra$ a $ell la+elled diagram of a "omposite "one.

+) -ra$ a diagram sho$ing three intrusive vol"ani" features.

3. Give the importan"e of vol"ani"ity to man.

An#/er# to Acti+it0 .=

1. a) !ol"ani"ity is the eruption or sipping of molten magma from the earths "rust

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through faults Jvents.

+) E'trusive features of vol"ani"ity areD

1. !ol"ani" mountains lie "omposite "one& %sh and "inder "one& and lava "one.

. 2ava plains

3. 8raterJ"alderas

4.


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3. ,mportan"e of vol"ani"ity to man.

#ourism due to attra"tive features.

Soil favour agri"ulture

8rater laes for mining (salt) ?ighlands modify "limate.

>ater for domesti" purposes from the 8rater 2ae.

Forests on the highlands for various purposes.

Iuarrying of ro"

Spas "uring diseases.

Study purposes.

Acti+it0 .>

1. /olten ro" that has for"ed its $ay to the earths surfa"e leads to the formation ofD

%. ,ntrusive features.

*. -yes and sills.

8. !ol"ani" features.

-. ,ntrusive and e'trusive features.

. /ost laes in East %fri"a $ere formed due to:

%. #e"toni" %"tivity

*. -eposition.

8. -amming.

-. Gla"ial a"tivity.

3. #he feature formed $hen magma "ools along a +edding plane is "alled a:

%. -ye

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*. 2a""olith.

8. *atholith

E. Sill

4. /t. 6iliman0aro is an e'ample of:

%. a vol"ani" plug.

*. an e'posed +atholith.

8. a +lo" mountain.

-. a "omposite vol"ani".

5. #he e0e"tion of solid& liuid and gaseous material from the earth "rust to the surfa"e

is "alled.

%. Faulting

*. #e"toni" a"tivity.

8. !ol"anity.

-. !ul"ani"ity.

B. % granite done shaped feature found at the +ottom of mountains is "alledD

%. Sill

*. *atholith

8. -ye

-.


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-. 9apa.

. #he follo$ing are intrusive vol"ani" features e'"ept.

%. Sill

*. 8one

8. *atholite

-. -ye.

1@. >hi"h of the follo$ing is an e'ample of an a"tive vol"ano.

%. /t Elgon

*. /t 6enya

8. /t 6iliman0aro.

-. /t. 2angonot.

11. >hi"h of the follo$ing forms of energy is asso"iated $ith areas of re"ent

vul"ani"ity in 6enya.

%. #idal energy

*. Solar energy

8. Geothermal energy

-. ?ydro ele"tri"ity.

1. #he "aldera on top of mount.manegai near 9auru is a result of a vol"ani".

%. /ountain petting e'tin"t.

*. /ountain erupting freuently.

8. /ountain vent getting sealed.

-. /ountain getting sun.

13. >hi"h of the follo$ing features is not a vol"ani" landform.

%. % gra+en

*. *atholith

8. Sill

-. 2avaplain.

14. % feature formed $hen lava solidifies in a vent is "alledD

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%. 2ava plain

*. !ol"ani" plug

8. 2imestone

-. Granite.

15. /olten ro" $hi"h has for"ed its $ay to the earths surfa"e leads to the

formation of:

%. ,ntrusive features

*. -yes and sills

8. !ol"ani" features.

-. E'trusive features.

1B. % vol"ani" eruption is more liely to +e violet $henD

%. #he vol"ano is near the sea.

*. #he ne" of the vol"ano is sealed +y a plug.

8. #he lava is vis"ous.

-. #he lava rea"hes the surfa"e through fissures.

1C. >hi"h of the follo$ing statement des"ri+es the pro"ess of vul"ani"ity.

%. >hen magma and gaseous materials are intruded into the "rustal layers.

*. >hen magma and gaseous materials are e'truded into the "rustal surfa"e.

8. >hen magma and gaseous materials are e'truded into the earths surfa"e.

-. >hen molten ro" and gaseous materials are intruded into the mantle.

1. >hi"h of the follo$ing layers of the earths stru"ture is asso"iated $ith the origin

of molten magma.

%. #he lo$er and upper layers of the "rust .

*. #he upper and lo$er layers of the "ore.

8. #he upper and lo$er layers of the sima.

-. #he lo$er and upper layers of the mantle.

1. #he steam 0ets $ithin ol donyo lengai indi"ate that vol"ano isD

%. -ormant

*. %"tive.

8. E'tin"t

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-. 9ever erupting.

An#/er# to Acti+it0. >

1. 8 11. 8

. % 1. -

3. - 13. %

4. % 14. *

5. 8 15. 8

B. * 1B. 8

C. * 1C. 8

. % 1. *

. *. 1. *

[email protected]

earth movements tch r

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