“Why do volcanoes erupt?” asks Silas and Zakk (10)


Thank you Silas and Zakk for your question. My team are correct it’s all about pressure. All volcanoes have a thin ‘lid’ of solid rock which which is solidified magma. Underneath the lid is lots of molten magma which is heated by the Earth’s central core.

Things can happen to this magma. Some of it could cool, and solidify. You could also get convection currents like you do in any hot liquid. These can increase the pressure (push) on the volcano lid, break it and the pressure is released like the liquid in a bottle of fizzy drink.

Want to make a comment, please make it in the box below. Not sure about something …ask another question.

(revised 13/9/17  Magna misspelling and added support text)

Elizabeth (9) asks “How does sand form in a desert?”

I agree we need to do an investigation.  The suggestion is that the desert sand might have come from the soil. Let’s see if we can find sand in the soil around us. Before we do this lets think about soil, the soil in your garden. What do you think it is made of? Maybe it is just made of soil? Maybe it is made of a mixture of things? Let’s investigate these questions.

Collect some soil. Get a plastic transparent beaker or a jar with a lid. Put a couple of small spoonfuls of your soil into the container. Add enough water so that it is half full. Cover and shake for about 20 seconds. Put it down and wait for about fifteen minutes. Now look at it and make notes on what you see. Repeat with another sample and another beaker or container (investigations always need to be checked).

Has your experiment resulted in layers of stuff in the beaker? Maybe a bit like the layers in the image below.

If it has then think about why you have layers? What has formed the first layer and why? Was it because it was the lightest or heaviest ‘stuff ‘ in the jar (soil)? Is the second layer made up of ‘stuff’ that is lighter or heavier?

The bottom layer is ‘sand’ …..the heaviest ‘stuff’ that makes up soil. The other layers are ‘silt’ and ‘clay’. Look at the diagram that my friends have given you the sand particles are the biggest.

Now to deserts. In very arid (dry) conditions the soil dries out. The wind basically blows away the smallest particles of clay and silt leaving the largest so a desert of sand is formed.

Elizabeth … thank you for your question.

‘How many volcanoes can go off at once’ is Charlotte’s (9) question

Charlotte it might be worth reminding ourselves of what is a volcano, and why do they occur. I’ll let my friends start the discussion.


Some interesting thoughts team but we have to look at Charlotte’s question.’How many volcanoes can go of at once?’ Firstly there are recorded to be 1500 volcanoes in the world as we know it. There are also lots of volcanoes under the sea but we don’t know how many. Of the 1500 about 500 have been active over the last 100 years. So Charlotte,  it is quite difficult to give you a definitive answer. For a volcano to erupt there needs to be some activity in the magma (the molten core of our Earth) and maybe the tectonic plates (the mantel plates that make up the surface of our Earth). Where the plates meet there is lots of tension, this normally causes earthquakes (New Zealand) but could allow magma to escape via a volcano.

“What is the earth made out of” – asks Ruby (8)

Ruby, many thanks for the question. Now let’s think about what it means. Does it mean the ‘earth’, like the soil that we have around us OR does it mean the ‘Earth’, the planet that we are living on. I say on my front page  that science is all about asking questions, but asking them is not always an easy task, so well done you. I shall get my friends to try and answer the ‘earth’ question and I shall then give you an answer to the ‘Earth’ question. We might even find something for you to do!



So maybe you could find out something about how easy it is to break a rock up? How about making a small collection of some rocks. They are quite easy to find at Garden Centres, or on walks in the country, or on a stony beaches. Collect some and then try to scratch them. Can some rocks scratch other rocks? If they can which is the hardest? try to draw a picture of your hardest rock. It is most likely that it will be the softest rock in your collection that you will find in your ‘earth’.

Now Ruby let us look at the ‘Earth’ and the wonderful structure that you are standing on. This is where your rocks have come from.

I have built this small animated picture to show you the amazing ‘inside’, structure of the Earth.