Forming fjords

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Transcript

What happens when you’ve got a glacier occupying a valley during a period of very cold climate is that the ice in the glacier, it plucks away, it erodes the valley in which it’s sitting, and rocks and pieces of rock get torn away from the side of the valley by the freezing and thawing action of the ice. The rocks then fall into the crevasses in the glaciers and they work their way down to either the base or the side of the glacier and then, in the process, they also are breaking down because of the freezing and thawing action of the ice. And they eventually form like a sort of sandpaper which abrades at the bottom of the glacier and it sort of erodes, basically erodes the valley away, scratches the valley away. And as the glacier is moving, it’s very slowly but it is moving, this slowly scours out more and more of the valley, creating these sort of u-shaped, long, linear features which eventually open out into the sea.

And a glacier itself may occupy one valley, the main glacier may occupy the main valley but then, coming into the main glacier, you might have little, smaller glaciers feeding into that main glacier. And they often occupy valleys which were once filled with rivers or streams. Then, with the colder weather and the colder climate and the ice building up they have, those streams have become mini-glaciers if you like. And so, when you do visit an area which is full of fjords you often can see these smaller glacier valleys coming in higher up the fjord with lovely waterfalls and things, because, if the glacier’s now melted, most of it’s melted, these valleys are left there hanging on the side of the main glacier and you get these lovely waterfalls.

I recently went to a fjord for the first time - surprisingly, although I’ve known about them for so long - and what struck me, the first thing that struck me was how beautiful they are. That they’re like these long thin, thin but wide, u-shaped valleys that are flooded with water. You can sail into the fjord, and at the head of a fjord you find the glacier. Even in these days when we talk about global warming you can still see the glaciers in parts of Scandinavia. The ice is a lovely, turquoise blue colour, which is surprising. I was really surprised by the colour of that. And that’s caused by very, very small particles of rock, what we call rock flour, which is ground up rocks, which imparts that sort of blue colour to the ice, and also when the ice melts of course it goes into the, it melts and goes into the fjord and the waters of the fjord are also often a lovely turquoise colour.

You can see, at the end of the glacier, lots of debris, rock debris, which is coming out of the glacier. As the glacier is melting it retreats, and there are streams that come out from underneath the glacier and with them they bring all this sort of rock, fragments of rock which have been plucked away from the side of the fjord and they get deposited on the floor of the valley, really.