We've been on a big geography bender this week; after Jenson's epic pollution project we moved onto river formations and their origins.
By reinterpreting this diagram, Jenson reconstructed the different stages of a river - from its source in the mountains to its outlet in the sea. He learned that most rivers start high up in mountains and hills. Some of the water runs over the ground in small channels. These channels join up and form a stream.
He began by building a big mountain which he covered in blue Lego blocks to represent the water. We talked about how the stream rushes down the hill carrying pebbles and gravel, which carve a channel into the ground. As the stream moves downhill it is joined by others and soon the young river is a cascading torrent.
The white Lego bricks that the trees are stood on is a gorge. Jenson noticed the white rocks in the diagram and copied it. He has great attention to detail. I explained to him that gorges are formed when soft rock is worn away as stones and boulders are swept along and pile up to form rapids.
Jenson added large green plates to show how the ground starts to level out as the river leaves the hills. Large side streams, called tributaries, join the main stream as indicated by the darker blue pieces of Lego. The valley sides become gentle slopes as the mature river slows and flows more smoothly.
As the land becomes flatter, the river starts to curve from side to side. It forms large loops, called meanders. On the outside curve of each meander the river flows fast, eating away at the river bank and making the loop larger. On the inside curve it flows slowly. Sediment which has been cut away from the bank is dropped here. Eventually the meander is cut off from the river and forms an ox-bow lake. Jenson built this ox-bow lake below.
He used this diagram to understand what types of animals and plants might be found in ponds and lakes.
Jenson used slightly large, flat blue bases to show how the river widens by the time it reaches the sea. It carries huge amounts of soil that has been eroded from the river banks. Much of it is dropped in the estuary where it forms mudflats and sandbanks.
Also this week Jenson built a super LEGO pirate ship, which he made off the top of his head.
I particularly like his attention to some of the details - the figurehead for instance and the wheel of the ship that could actually rotate 360 degrees.
The plank was also a fantastic piece of Lego engineering. Jenson had noticed that on other pirate ships the plank would be hoisted in when not being used. He had worked out a way to make it move by using flat 2x2 pieces therefore allowing it to slide in and out.
He also built an anchor. The shape of it alone was impressive but he also worked out how to make the winch system to allow it to be reeled in and out.