Tag Archives: convection


Dear Heather and Keira,

I never know when a post or comment from a student or class might prompt an extended comment. Something written makes me recall some information I have read or seen over the years and before long I find a comment growing longer or I want to include photos, videos, audio or links.

In the "How did the Earth begin?", the challenge was one I thought I could meet. Being keen on science and many other things, I had been following theories on the origin of the Earth and the universe. Once I have an idea for a post, I research my facts to try to make certain my thoughts are on the right track then start writing the post. I knew "How did the Earth begin?" would be a longer post because there is much to consider.

Geocentric is a term used to describe the belief the Earth is the centre of the universe and all planets, stars including our sun, and the moon orbit us. From research, I have found many people still believe in geocentrism today. For some, it may be a religious decision, others a firm belief they believe science can support, and for others it's more a matter of not knowing any other way.

We do live on the crust of the Earth. It's the solid part that is our land and the bottom of oceans and seas. Compared to the rest of our planet, it is very thin but I wouldn't have it any other way. If you cut an apple in half, you can see the thin skin (like the Earth's crust) covering the rest of the apple down to its core.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

The inner core is thought to be very hot but solid iron hotter than the surface of the sun. It's pressure keeping it solid. The outer core is still mostly iron but it is liquid and flows around the inner core. Remember, the Earth turns on its axis and this causes the spin and also gives us night and day. Think of stirring a drink. You can see the liquid moving around as you stir.

It's this movement of the outer core that gives our planet a magnetic field and protects us from much of the sun's dangerous radiation. Mars doesn't have this activity so has a weak field. Even if there was air to breath on Mars, we would probably still need special clothing to protect us.

The mantle is semi-liquid and is basically moving hot rock (magma).

Schools and students have permission to use this graphic for non-commercial, educational purposes.

The mantle movement is known as convection. We can see this effect in boiling water. Below is a video clip I prepared for you. To see the movement of the water, some rice grains were dropped into the water. You can see them move to the side being heated, rise with the heated water then sink back down as the water cools a little. The same thing happens in the mantle. The hot rock (magma) sinks down as it cools a little, is heated near the outer core and rises again. There are many of these convection currents in the mantle not just one big one.

Schools and students have permission to use this video clip for non-commercial, educational purposes.

Sometimes this movement of the magma brings magma to the surface and it flows out as lava. I was on Hawaii (The Big Island) a number of years ago and took a helicopter ride over the Kilaeua and along the coast. Look in the photo below and you see see the lava pouring out into the sea. Kilaeua has had a very active period.

The photo is a scan of an old 35mm slide so the quality isn't the best.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Location: Kilaeua, Hawaii, U.S.A.

Curiosity is a great gift. It's something still driving me to explore new ideas and things. I can see you both have curiosity. I wonder what great discoveries and learning is ahead for you? 🙂