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Natural sciences

Planet earth and the universe

The earth

Educator section


Assignment 1:

  • Assess using the assessment matrix.

Assignment 2:

Main Ideas

  • Earthquake: evening of 29 September 1969.
  • Registers 6.5 on the Richter Scale.
  • Chaos in most places.
  • Rumbling grew louder and louder and was followed by tremendous quake.
  • The whole earth shuddered and people ran about panic stricken.
  • Rescuers used the Post Office as a base because it was the only place which had electricity.
  • Homes were badly damaged and people were badly injured.
  • Emergency aid streamed to the disaster towns and the police and army co-operated.
  • People were housed in tents and field hospitals were erected.
  • The water shortage was alleviated and food was supplied.
  • R13 million donated by the Disaster Committee

Assignment 3:

  • (sketch)

Assignment 4:

1. The Richter Scale is the instrument (scale) which seismologists use to measure the strength of an earthquake.

2. Seismologists are scientists who study earthquakes.

3. The place at which the shock waves first reach the surface of the earth is known as the epicentre.

4. If the pressure in the mantel under the crust builds up then magma is forced through weak places and cracks. These weak places then form volcanic pipes.

5. Active volcanoes are volcanoes which erupt from time to time.

Leaner section


Activity: to analyse the structure of the earth and to measure movements in it (natural disasters) [lo 2.1, lo 2.3]


  • Scientists believe that Earth came into existence about 4 600 million years ago as a large cloud of gas and dust swirling around in space. While it was rotating it shrank to an extremely hot, liquid ball. The surface gradually cooled and a crust of solid rock formed which weathered to the mountains, soil and sand on which we live today.
  • Earth is continually changing. The land masses (continents) are not only moving, but new crust is forming all the time. The movement of the crust is called continental drift and it is still occurring. America, for example, is moving gradually away from Europe. This movement has already led to telephone cables under the Atlantic breaking.


  • The Crust

The crust is the outermost layer and has a thickness of from 5 km to 70 km. Under the oceans the crust can be as thin as 5 km and where there are mountains the crust can be as thick as 70 km. Beneath the crust there are three other layers. They are:

  • The Mantle

The mantle is 2 900 km thick. It is solid but contains slowly flowing currents of semi-melted metals.

  • The outer Core

The outer core consists of liquid metal and is responsible for the earth’s magnetic field. It is 2 240 km thick.

  • The inner Core

The inner core in the middle of the earth is probably solid and consists mainly of metals. The temperature is 3 700 degrees Celsius. Water boils at 100 degrees Celsius. The inner core has a diameter of 2 240 km.

The lava that flows from volcanoes comes from the mantle.


Use playing dough (four different colours) to make a model of Earth’s structure. The thickness of each layer should be more or less proportional to the actual thickness of the earth’s layer.

Questions & Answers

can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
I'm not sure why it wrote it the other way
I got X =-6
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
Commplementary angles
Idrissa Reply
im all ears I need to learn
right! what he said ⤴⤴⤴
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
is it 3×y ?
Joan Reply
J, combine like terms 7x-4y
Bridget Reply
im not good at math so would this help me
Rachael Reply
I'm not good at math so would you help me
what is the problem that i will help you to self with?
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Natural sciences grade 7. OpenStax CNX. Sep 16, 2009 Download for free at http://cnx.org/content/col11077/1.1
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