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Sosiale wetenskappe

Graad 7

Natuurgevare

Module 4

Vulkane

1. Vulkane

1.1 Die voorkoms en oorsake van vulkane.

Die gesmelte rots onder die aarde word magna genoem. Wanneer dit op die aardoppervlakte uitvloei, word dit lawa genoem. Oor die presiese oorsake van vulkaniese uitbarstings dink die geleerde mense egter nog nie eenders nie. Niemand kan in die hart van die aarde gaan kyk wat aangaan nie.

Ons weet wel dat die aardkors so swaar op die magma van die mantel rus, dat hierdie vloeibare rots byna soos ‘n pitseer se pit deur ‘n swak plek in die aardkors na boontoe gedruk word. Hierdie gesteentes het ‘n temperatuur van tussen 800ºC en 1 500º C.

As jy ‘n gaskoeldrankblikkie vat en jy skud dit, sal die koeldrank uitspuit as jy dit oopmaak. ‘n Vulkaan werk presies dieselfde – gesmelte rots bars deur die swak plekke in die aardkors en die lawa, rotsblokke en as word die lug ingeskiet.

Die lawa stol en vorm nuwe rotse wat ons stollingsgesteentes noem.

Party vulkane se lawa is baie loperig en vloei ver oor die oppervlakte voordat dit stol. Dun plate stollingsgesteentes word so gevorm. Ander vulkane bou weer ‘n koepel op omdat die lawa taaier is en dus nie ver kan vloei nie.

Soorte vulkane

Met ‘n geweldige uitbarsting kan die koepel se kop heeltemal weggeskiet word en ‘n oop gat ontstaan wat ‘n kaldera genoem word.

Vandag is daar maar ± 450 aktiewe vulkane op die aarde. Hulle hou gelukkig nie altyd aan met uitbars nie en word dan rustende of passiewe vulkane genoem.

Waar kom die meeste vulkane voor?

Daar is sowat 500 vulkane in die wêreld en hulle kom net op sekere plekke voor. Hierdie plekke lê op die rand van die groot plate van die aardkors. As hierdie plate beweeg, ontstaan vulkaniese uitbarstings en aardbewings.

Die verspreiding van die vernaamste vulkaan- en aardbewinggebiede van die aarde

Watter vulkane het die meeste verwoesting aangerig ?

Die vulkaan wat die ergste verwoesting nog aangerig het, is Krakatoa in Indonesië. Dit het in 1883 uitgebars en meer as 36 000 mense het gesterf. Die knal is 5 000 km ver gehoor en die lugbesoedeling het vir jare nog koperkleurige sonsondergange op die aarde veroorsaak.

Nog ‘n bekende voorbeeld van ‘n verwoestende vulkaan is die uitbarsting van berg Vesuvius, wat in 79 n.C. die stad Pompeji in die Baai van Napels heeltemal onder vulkaniese rotse en as begrawe het.

2. Die uitwerking (gevolge) van vulkane op mense se lewens en hul sosio-ekonomiese aktiwiteite

In die swart hemel van die nag vonkel duisende liggies. Op ‘n afstand lyk dit na ‘n ontsaglike vuurwerkvertoning soos die vulkaan in gloeiende rotse en strome van vuur ontplof. Rotse en as word die lug in geskiet en veroorsaak lugbesoedeling.

Oor die rand van die krater kruip die rivier van rooi, rokende lawa – warm bloed van die lewende aarde, soos iemand dit al treffend beskryf het.

Kilometers ver vloei dit miskien deur vrugbare valleie, verteer dit elke grashalm en selfs bome op sy pad. Maar ook huise verkrummel en stede word onder die voortstuwende gloed begrawe. Mense wat dit oorleef, vlug van die hange af ; warm as reën op hulle neer. Lewensverliese kom ook voor omdat mense versmoor as gevolg van die verstikkende swaelgasse en asreën wat ontstaan.

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
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Source:  OpenStax, Aardrykskunde graad 7. OpenStax CNX. Sep 09, 2009 Download for free at http://cnx.org/content/col11020/1.1
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