ACE

Today's lesson started with a recap on the key points that we have studied on rocks. Then, Ms J told us about fieldwork, when you go out to find evidence. Ms J told us about what we will be doing when we upgrade to upper secondary (regarding fieldwork). She reminded us that Geography is not just about what the teacher says in class, it is, most importantly, about skills, interest and all. How true!

Then Ms J started lesson proper. We learnt one new topic about Geography, and that is the Layers of the Earth. A little summary:

Crust- Solid outermost layer, separate pieces called plate

floats on

Mantle- Liquid/ Molten

Core- Solid centre

How to remember? Just remember the Ferrero Rocher : ( picture from Wikipedia)
The small circle in the chocolate: Inner Core
The circle surrounding the small one: Outer Core
The thick darker brown big circle: Mantle
The outer layer: Crust




Cool, right?

The mantle is >200 degrees C (that's super hot!) and the core is 5000 degrees C (that's super super super hot!). The core is interestingly the hottest thing on Earth! Can't imagine how hot it is? Maybe knowing that the Sun is 5000 degrees C might help you!

Here is a website regarding the temperature of the middle of the Earth: http://hypertextbook.com/facts/1999/PhillipChan.shtml

Then one of us asked Ms J how do scientists find out about the three layers. It was then Ms J gave us our first assignment, to find out for ourselves . We have researched, and here is the answer, taken from http://au.answers.yahoo.com/question/index?qid=20080413155742AAz6Egs :
"I'm guessing your talking about the inner core, outer core, etc...Earthquakes produce two different waved pressure waves (P waves) and shake waves (S waves), these waves are picked up all over the world after an earth quake.When an earthquake happens there would be shadow zones where no waves where picked up or only P waves where picked up... the face that S-waves where completely blocked by the core meant that there needs to be liquid... the fact that there is P wave shadow zones proved that the core is not completely liquid and there is a inner core which is solid.The shape of these shadow zones tell us the size of the inner and outer cores and in part their densities."

Understand? :)

And then the next big question came out, Why is the solid centre (Core) solid? To research was our next assignment, and to prove that we have done our homework, here is the short but direct results of "Why is the earths inner core solid?" from http://answers.yahoo.com/question/index?qid=20070620064611AAsJULg:
"The incredible pressure does it despite the great heat down there. ~Heat liquefies, pressure solidifies."

Then Ms J tells us something cool and interesting- there are earthquakes everyday (because of the moving crust), it is just a matter of how strong the earthquake is. Bet you'll only know that if you study Geography!
The crust is like the jigsaw puzzle on the Earth's surface. The plate boundary is where major natural disasters occur, such as flooding. Since Singapore does not experience any, does that mean we are not living near the plate boundary?
Anyways, another question popped out: What happens if plates hit each other? To know the answer, just stay tuned to the next lesson!
This lesson was great, as many interesting questions came out and thus we were able to learn more interesting stuff. It would be great if the lessons would forever be like that, with many smart questions being asked and answered. Geography is indeed one of the most interesting subject anyone can ever learn!