Earth Science - Structure of the Earth and Plate Tectonics

Read the Meredith Hooper Book 'The Island That Moved' - this is a little long winded for younger listeners, you can shorten the story a bit by paraphrasing it onto post-it notes ready to read to them. Then we sat around together and I reminded the children about the end of our last session when we made a fossil sandwich.....

Do you remember the last time when we talked about fossils and how they were buried under the earth? Do you remember the fossil sandwich that we made? How do you think that those fossils made their way to the surface of the earth to be collected by palaeontologists? Fossils of sea creatures have been found up mountains, what happened to get them up there? (talk about the children’s answers and work towards the earth moving. The story starts way below us at the centre of the earth……  Here is a model of the earth; I’m going to cut it open for us to see what’s inside! (show the play dough model of the earth and cut it open in front of the children for them to see the layers).

There are four layers to the earth:

·        This is the inner core (yellow), it is made of solid metal and it is super-hot.

·        The outer core (orange) is liquid metal and is also very very hot, it is under immense pressure, being squeezed and pressed by the weight above it.

·        The mantle (red) is cooler and more solid than the outer core, but it is liquid enough to be slowly moving all the time, like thick cake mix being stirred through by a wooden spoon, (speaking of cake mix, I made some earth cakes for you to try, break them in half and see if you can identify the layers of the earth).

·        The crust around the outside is made from jigsaw-like plates of rock called tectonic plates that move around very slowly on the mantle and bump into each other. Scientists think that millions of years ago, all of the earth’s continents belonged to one super-continent called Pangaea (show the children the globe with the continents on it, and then give them the felt continents to try and piece together on the zigzag construction paper. Once they have pieced them together then slowly pull the construction paper flat to show the continents moving apart from each other again)
 

As the tectonic plates move around on the slow-moving magma below (show the map of the tectonic plates), they bump into each other and different things happen (ask the children what they think might happen). From that, four different types of mountains can be formed:

·        Fold mountains occur when two plates collide head on and push against each other. The huge forces involved push the rock up and it folds and creases as it goes (show the children the demonstration with the towels).

·        Block mountains form when two plates rubbing together suddenly shift, they may have been caught for a long time then the rock suddenly gives way and the plates jump past each other. This often leaves a huge block of rock pushed up or one side of the fault jutting up. The shock waves from the sudden jump cause an earthquake (show the children the card moving in the jar of rice layers)

 

·        Dome mountains are pushed up  by magma, the molten rock is pushing at the solid plate from below and causes an enormous bulge to form in the earth (blow up a balloon covered by a towel with a piece of pipe, a bulge will form in the towel).

·        Volcanic mountains form when molten magma from the outer core and the bottom of the mantle forces its way up through the mantle and through a weakness in the tectonic plate(show the children the volcano model and demonstrate the reaction – remind to put goggles on). It either explodes out of the top with huge force, or trickles out gently and continually. Either way, the magma cools once on the surface and new layers of rock are now present. Under the ocean where oceanic plates move apart from each other, magma moves up into the gap and forms new ocean floor (demonstrate this with the crackers and the red jelly layer).

 The children were all keen to have a go at the practical models, and with their parents sitting around the table helping them out and talking about it with them, there was lots of great chatter and review of important concepts and words. Even the toddlers enjoyed the cracker 'plates' on jelly 'magma' (although they did end up eating most of it!)

 Predictably, the volcano was the most popular activity, and it did get awash with foamy magma after a while and the concrete mix that made the sides of the volcano slid off and ended up in the bin!!

 If I ever see another pan of play dough again I might cry but it was worth all the effort of making bags ful of different colours as the families all made their own play dough earth to take home and the children were really pleased with it! Once again I sourced ideas from various books and websites, adapting some of them. I used ideas from The Homeschool Den, the book 'How the Earth Works' and various pinterest sources which can be found on my pinterest science board (some ideas like the play dough earth have been done in so many ways that the original source is impossible to say!). I have saved the scripted session as a google document for you to use, to access it, you need a gmail address/google account - you don't have to use the gmail, just sign up to be able to access my documents! It was a more effective way of sharing with you than saving PDFs to a remote location!