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Sosiale wetenskappe: aardrykskunde

Graad 7

Natuurgevare

Module 3

Aardbewings

1. Die voorkoms en ontstaan van aardbewings

Een wetenskaplike wat self ‘n sterk aardbewing ervaar het, het op ‘n keer vertel dit het vir hom gevoel of die hele wêreld ‘n mat geword het wat ‘n slag of wat goed geskud en toe weer neergegooi is. Die mense, die geboue, die berge - alles en almal was niks meer as stoffies in daardie mat nie, het hy gesê.

[uit Huisgenoot se Jongspan , 21 Mei 1987]

Jy moet onthou dat die aardkors opgebou is uit groot plat rotsplate. Hulle is kilometers dik en dryf bo-op die dik, warm massa magma van die mantel. Hierdie bewegings is baie stadig en ‘n mens kan dit nie voel nie. Die rotslae van die aardkors wat nader aan die mantel lê, is warmer en buig maklik. Nader na die oppervlak van die aarde is die gesteentes kouer en dus harder.

Waar die aardplate mekaar ontmoet, bots hulle of skuur hulle teen mekaar. Wat ook al die rede vir die bewegings in die rotse is, sal hulle nie net buig of plooi nie. Hulle breek letterlik af soos wanneer jy ‘n stukkie hout in twee sal breek. Die aardkors kan vir ‘n tyd lank die spanning en druk weerstaan wat deur die bewegings binne-in uitgeoefen word. Skielik kan dit nie verder plooi nie en breek af. ‘n Verskuiwing van rotslae vind plaas en mense ervaar dit as ‘n aardbewing. ‘n Verskuiwingslyn word gevorm wat selfs bo-op die aardoppervlakte gesien kan word.

Aardbewings duur slegs ‘n paar minute en naskokke kom ook nog vir ‘n tydjie daarna voor.

Die bekende San Andreas-verskuiwingslyn loop dwarsdeur San Francisco in die Amerikaanse staat Kalifornië. Miljoene mense woon hier en is bewus van die gevare.

In figuur 5 word aangetoon hoe die reuse rotsblokke baie stadig by mekaar verby skuif (5 – 7 cm per jaar). As die kante aan mekaar vashaak (spanning word te hoog), skuif die rotse skielik en breek af. Die gevolg – ‘n aardbewing het voorgekom.

Die San Andreasverskuiwingslyn

‘n Seismograaf word gebruik om die sterkte van ‘n aardbewing te meet

Aktiwiteit 1:

Om ‘n model van ‘n aardbewing te bou

[lu 2.1, 2.3]

1. Maak ‘n model van ‘n aardbewing: Werk in groepe. Kry twee ewe dik houtplanke en plaas hulle langs mekaar. Maak boublokke van karton wat bakstene, huise of geboue voorstel. Plaas die boublokke oor die verskuiwingslyn (daar waar die twee houtplanke aanmekaar raak). Trek nou die planke weg van mekaar of in teenoorgestelde rigtings.

2. Verduidelik wat presies met die blokke gebeur?

3. Wat word die verskillende stukke (die twee houtplanke) waaruit die aardkors opgebou is, genoem?

4. Wat dink jy kan gedoen word om geboue meer bestand teen aardbewegings te maak. Hou ‘n groepbespreking en doen dan verslag aan die klas.

Waar kom die meeste aardbewings dan voor?

Aardbewings kom veral voor op die rand van die aardplate – daar waar die aardplate stadig na of van mekaar beweeg. Die bewegings veroorsaak dan aardbewings in die lande bo die rand van die plate. Lande wat in die middel van die plate lê, word nie ernstig deur aardbewings bedreig nie.

Suid-Afrika lê in die middel van ‘n aardplaat en sal dus nie sommer ‘n groot aardbewing beleef nie. Nogtans is roeringe in die aardkors se mantel ook hier aanwesig. Dink maar aan die Bolandse aardbewings by Ceres in 1969, wat baie skade aangerig het, asook die aardbewings by Stilfontein in Maart 2005.

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
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Cied
what is biological synthesis of nanoparticles
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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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