Saturday, 23 February 2013

Scripted Earth Science/ Geology session on Fossils

Science is 'my thing' but I didn't realise until recently what a gift it was to understand it easily and how many other parents didn't feel very comfortable with it. With this and my 2013 goals in mind, I offered to put some things together for a new monthly home ed group that we are involved with. Here is the basic script that I wrote (it was embellished and altered as we went according to the children's responses!). The PDF of this session is available here
Beginning – Story Sandwich
Tell the story of coastal animals that met grisly ends and encase them in a bread layer as I talk – shaped marshmallows for jellyfish, flat laces for seaweeds, milk bottles for fish, chocolate mice for shelled ammonites, cover it in plastic, put heavy books on it and come back to it later.
Part One – What is a fossil?
If I wasn’t here any more and you wanted to tell a stranger about me, what would you say? How would you describe me to them? (blue eyes, brown curly hair, clothes wearing, woman etc)
Show children the picture of the fossilised dinosaur – What can we tell about what this dinosaur was like? (big, had horns, teeth etc) What about the colour, the pattern on the skin, did it have fur or scales? How do we know? Do we know for sure or are we guessing? (discuss children's ideas)
We struggle to answer some of these questions because when an animal was fossilised, not all of the animal became the fossil. Which bits do become fossilised? (bones/teeth) What happens to the other parts? (eaten/rotted).
Have you ever watched a wildlife film where a lion kills an antelope or something and lots of animals come and pick at the carcass until there are only bones left? Do you think that happened to dinosaurs?
What if the animal died by a river and then there was lots of rain and the river burst its banks and a huge torrent of water rushed down and swept the bones away? What might have happened? (demo this with remains in tray and jug of water as the ‘torrent’ washing them away) It splits the bones up/spreads them out so they aren’t altogether as one skeleton.
Do you think it is easier for palaeontologists to guess about the animal if the bones are altogether or scattered down the riverbed? (lead them to suggest easier if not scattered) Why is it harder if they are scattered? (because like a jigsaw to put back together – demo putting the ‘bones’ back together the wrong way to make a silly skeleton).
Play Fossilisation Game
Children are given roles to play that match the coastal creatures in the story – seaweed (waves), fish (wiggle and blow bubbles), jelly fish (bob up and down), ammonites (twizzle round), Flying dinosaur (flap arms and squawk), sea predator (shark fin and ominous noises made).  Shout ‘go’ then ‘freeze’ and walk around, touching various creatures on the head and announcing the grizzly end that they met and which meant that they weren't fossilised e.g. seaweed rots, jellyfish washed away, fish eaten by flying dinosaur, etc etc. Shout ‘go’ again and continue until only two left – ammonite (buried in a mud slide) and sea predator (dies from old age, sinks to the bottom and is covered with sand brought in by a coastal storm).  Explain to the children that this shows that not many animals became fossils, it was actually very rare for it to happen and they are pretty special!
Part Two – How do Fossils Form?
So we know that fossils are the remains of ancient creatures and it is rare and special, but HOW does it happen? How does this (hold up dinosaur) become this (hold up dino skeleton), (talk about answers the children give).
Have a look at some fossils that we have and some pictures. There are different ways that animals and plants become fossils, and I’ve set up some activities for you to have a go making some of them for yourself take the children to the activity table and go round it, talking them through the types of fossil.
There are impression fossils - imprint fossils, small thin things like leaves, feathers and fish became squashed in layers of sediment and rotted away, leaving the imprint of themselves behind and ‘mould and cast’ fossils where a bigger creature such as an ammonite was buried under the layers. It took longer to rot so kept its shape as the layers turned to rock. Eventually it rots and its size and shape is left exactly in the rock (the mould). The cavity can eventually fill up and this takes on the exact shape of the original animal (the cast) – demonstrate pulling one out of the mould.
fossil 'moulds' ready to be cast
Adding plaster of paris to the moulds to make a fossil 'cast'
There are trace fossils which are marks and tracks left by animals to show that they were once there but have moved on – these could be footprints, egg shells, coprolite (fossil poo) etc.
Making dinosaur footprints in playdough
Preserved organisms – encased in snow and ice like woolly mammoths, soft tissue preserved and doesn’t rot so know more about them. Also insects in sap, hardens to amber over time – hand out ‘preserved’ sweets in jelly cubes.

Mineral replacement fossils – familiar dinosaur bones, water seeps through rock, dissolves bones but leaves minerals in place, turning the bones to stone.
Breaking open fossil rocks

Part Three – How do People find Fossils?
Go back to the sandwich story and peel back layers, see what happened to the different fossils, which were cast and mould, which imprint, which mineral replacement etc – one at the bottom died first, would it be unearthed first or last by palaeontologists? Why? Talk about it, show activities – dinosaur dig in sand and brushes (mark on a grid if they like), coffee ground ‘stones’ with pasta pieces to ‘excavate’.
I used various books and websites for inspiration, many of the activities were adapted from the ideas I read, to suit the materials and the time that we had. Here are some of the links and further information:
  • Fossil sandwich idea, I used five pieces of bread and told a dramatic story as we went about coastal storms, mud slides, and strong currents, and embellished how the various animals died, I used different types of sweets to illustrate different types of organisms - after explaining the different types of fossils to the children, at the end of the script, we unpicked the sandwich to see how the sweets had fared and which type of fossil they thought each one was most like - then they ate them in a bit of a free for all!
  • River flood demonstration was my idea - I bought a sand pit mould set of a large dinosaur and arranged it in an underbed storage tray then 'washed it away' with a jug of water with the tray slightly angled, then the children could see how it would get jumbled up and try to rearrange it.
  • Fossilisation game adapted from here, I made it mirror the fossil sandwich story in what happened to the creatures as they were destroyed or fossilised. The children were enchanted with this game and asked for the post-it notes afterwards to play it by themselves!
  • Imprint and trace fossils were made with play dough and leaves, feathers, a large plastic fish with textured skin and dinosaurs to make footprints.
  • Mould and cast fossil instructions, I found that the ration of plaster of paris: water was roughly two:one to get a nice creamy texture. I made up enough moulds before the session for each child to choose one and make their cast in during the session to take home and allow to dry then paint if they wished. The picture below shows the moulds in the process of being made. I used shells and dinosaur sand pit mould pieces to make the moulds, and the kiwis were needed to weight them down into the plaster of paris as it set (which takes about 40 mins). I then popped them out to dry fully. The tin is a six hole muffin tin, my 'quarter cup' measure made about enough plaster to fill these moulds, the larger ones needed more.

  • Preserved organism jellies - I can't remember where I saw this idea, I made up some jelly with just over half the recommended amount of water and poured it into a sandwich box lined with waxed paper. I allowed it to cool for a short time then carefully spaced out small jelly sweets inside as the 'insects' with the jelly as the 'amber'. The children were cautious initially as I offered them a fossilised insect to eat but caught on quickly!!!
  • Coffee ground stones - I added more sand to this to make it grittier, and baked them for about forty minutes - we needed a small hammer to get into them, the pasta pieces inside weren't very successful, they broke up too easily or couldn't be extracted.... the fact that they go into the oven restricts what you can put inside them.
All told, it went really well, the children were eager to share their ideas and knowledge and loved the activities, there was a real hum of activity around the table afterwards and children of ages ranging from 19 months to 8 years anjoyed the hands on activities. All the families are keen for another session so watch this space for further earth science next month!!!

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