Catching up

Do most 8 year olds know the difference between sedimentary and igneous rocks? I think it was a bit crazy of me to assume this prior knowledge. And covering plate tectonics in one session was similarly overoptimistic. I have re-jigged both Nurture Learning sessions to address these issues.

The Friday group mostly concentrated on plate tectonics as they have already learned about rock types with me, in a previous term. We looked at different types of plate boundary and what might happen at each of them. We used household sponges to indicate the plates, and the mantle underneath. I was very pleased with the children’s insights (for example, working out that a diverging plate boundary would mean creation of new rock, or lithosphere). Next week I will reinforce this thinking by showing them a map of the age of the ocean floor in different parts of the world, and how it fits in with where we think the plate boundaries are.

In the Wednesday group we spent more time covering different rock types and how they form. We made use of this section of the BBC KS3 Bitesize website which has some good, simple designs of sedimentary rocks forming. I did one of my usual blurbs about how igneous rocks form (backed up by another picture). We watched the crazy ‘geodudes’ with their take on the Rock Cycle as seen by using sugar and other confectionery. Despite only being 2 mins long, this clip still manages to get in weathering and transportation of rock particles. Then the children looked at some of my rock samples to decide if they were sedimentary or igneous. (Metamorphic rocks are on my diagram of the rock cycle and I did mention them, but glossed over them somewhat.) This is always a popular activity and helps to bring the whole rock cycle out of the theoretical realm into the actual one.

We then made sedimentary rock models out of sand, water and plaster of Paris. We made them into layers and will test them out next week to see how they erode. Considering the potential for mess, the children were all brilliant and I am looking forward to the mess being contained next week too. (;-)) I hope they all enjoyed this.

The above took up a great deal of the time!! I wanted to show the Wednesday group an animation of the plates shifting over millions of years, but settled for a You Tube video of India colliding with Asia and the formation of the Himalayas. In the Friday group we also watched a simulation of the Himalayas being formed: 70 million years over 2 minutes.

Just to clarify, all the above fits in with our topic of “Changes to the Earth’s Surface” because the Earth’s crust and its geographical features are all made up of rock, and the rocks (although they may seem immutable) are always changing. Features get eroded, plates move around, mountains build up or break down, some plates are subsumed under other plates, new rock is created etc. The conversion of one type of rock into another is called the rock cycle, which I briefly showed to the children in the classes.

Next session we will have to test out our sedimentary rocks we made, and think about different forms of erosion and how humans can speed it up or slow it down. I might even get to finish talking about plate tectonics!

In the younger group, they have been thinking about measuring time and how we can date rocks and fossils. They had sand-timers and stopwatches and tried to work out how long each timer took. The Friday group seemed to have great fun timing each other running around. This is great – I don’t really mind deviations from what I have planned. It’s all learning, and if it is initiated by the children, so much the better. My Wednesday group did some wonderful drawings while the older children were busy with rocks and sand.

I talked to both sets of younger children about how scientists use radiometric dating to date rocks and fossils. The dating works if scientists know the half-life of a radioactive isotope, and what it decays into. They can then look at the relative proportions of the radioactive isotope and the final product. This is something we haven’t even covered with the older group! Please note, I didn’t actually mention the word isotope, just ‘element’, and we didn’t talk about ‘relative proportions’, so don’t worry too much that I’m overwhelming them. They didn’t seem overwhelmed.

We also looked at various events in the history of our solar system, from the formation of the sun to early rock art. The children tried to put the events in order on a timeline, and did a great job.

I am really enjoying these classes. All the children are all wonderful in their own individual ways, and I think the groups work together very well.

I invariably prepare too much material, but I would rather it be that way round than everyone twiddling their thumbs.

The Wednesday older group have in particular been very good at focussing for nearly the whole hour and a half. We generally only find the noise level creeping up towards the last 10 mins. I think this is great for a diverse group at this age and stage.

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The History of the Earth

A few billion years ago, the particles which would come to make up our planet Earth were simply hanging around in what is called the solar nebula, or the protoplanetary disk. Gradually, over a few more million years, these particles started to stick together, and the gravitational pull of the larger particles, plus their sweep through the disk as they orbited the sun, meant even more bits stuck on. This process was very slow but eventually our Earth was formed, something like 4.4 billion years ago. It had an interior of molten metal and a thin rocky crust. The crust survived many bombardments of meteors and the interior started to rearrange itself into the core and mantle as we know now.

This is roughly the story which I told to the older group in their second class this term. I had made a model of the Earth out of modelling clay, with its inner and outer core, and inner and outer mantle, and a thin crust.

I thought it would be good for the children to be aware that the crust of the Earth covers a liquid mantle, and that the crust is relatively thin compared to the rest of the Earth. I hope they will remember this when we start to talk about plates moving over the surface of the Earth.

I presented them with a very rough map of the world with the continents cut out in cardboard. I wanted them to follow the thinking of Alfred Wegener in the 1920s when he was trying to put together his theory of continental drift, taking account of the evidence of the time.

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I talked a bit about sedimentary rocks and how they can be evidence for the climate in that area at the time the rocks were formed. I also talked about fossils of the same type being found at great distances from each other, on different continents.

Each child designed a symbol for one of these pieces of evidence and they took turns sticking their symbols onto the world map. The aim was to use the map with symbols as a kind of jigsaw, trying to match up areas with the same sedimentary deposits, or the same fossils.

Everyone enjoyed their drawing and placing their symbols on the map. It was good to see the children coming to a kind of collaboration when they were rearranging the pieces. It is a good group to teach, although I feel I should still do more to involve the quieter ones.

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I had also mentioned volcanoes, so most of them wanted to draw a volcano or an earthquake too. We will stick these on the map next week when it will become clear that these tend to occur at plate boundaries. We will also talk about the different types of plate boundaries, and sea-floor spreading. We will briefly talk about how to date rocks, and start to build our models of sedimentary rocks ready for testing the week after.

The younger group, in the meantime, had been having fun looking at pictures of fossils, at samples of sedimentary rocks (sandstone) and playing with dinosaurs and modelling clay.

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We made saucer shapes out of the modelling clay and pressed plastic creatures in to make imprints. We then filled the saucers with Plaster of Paris to make fake ‘fossils’.12477705564_da47183268_n 12477702114_b9a2c6c15d_n