ah here we are so i'm here in the upper course of the river seven which is our gcse case study so we are in the up across the river what does that mean in the upper course of the river you tend to see a much much higher relief okay so up in the mountains here and you've got a higher relief so you've got water flowing down the river and it's flowing at surprisingly a much slower speed until we reach here a waterfall so a waterfall forms only really in the upper course river because of the sleep gradient but what happens we have hard rock followed by software when you have hard rock followed by soft rock and because we're at higher gradient the water's flowing down because of gravity and it starts to erode the softer rock through process of erosion abrasion and hydraulic action so hydraulic action is water going down you can see the water flowing there and as it flows over the waterfall or flows into the softer rock it erodes it but it goes into cracks as this water goes into cracks it starts to create high amounts of pressure and there's many explosions also the river will transport pebbles with it as these pebbles are thrown over the softer rock it starts to abrade it starts to rub away at the softer rock as this happens and the softer rock is being eroded it starts to create this overhang as it goes overhangs it goes into your plunge pool which you can see there where the water flows into as it goes into the punch pool closer erosion will happen on the back of the waterfall that then creates this overhang in time this overhang will get so far over the edge of this plunge pool that gravity comes into play and it simply can't hold its own weight and it will fall into the plunge pool as this process happens more and more so the river side waterfall starts to retreat backwards as this happens more and more it starts to create a landfill that we can see here at glenn hetherin waterfall that starts to create a gorge so to recap this four stage process hard rock followed by software the softbox is eroded by pros erosion hydraulic action and abrasion it starts to erode starts to create its overhang into the plunge pool as this happens the overhang gets bigger and bigger and the overhang will fall into the plunge pool creating as it retreats further backwards a gorge okay some beautiful jobs being action we'll be moving into the middle course of the river in due course there's some great chocolate actually