Black sand not polluted

SLN geography@Iceland 2003 Photo-enquiry 5

All photographs can be used in any teaching and learning context in a school but cannot be used for any other purposes without prior permission of kate.russell@staffordshire.gov.uk

5 How can sand be black and not polluted?

	5.1 How come this sand dune is black but not polluted?
	5.2 And it is not only the dunes but the beach too.
Low - High	5.2 Black sand – the movie version
	5.3 Is it because the rocks that the sea are eroding are all dark?
	5.4 Maybe that’s part of it.
	5.5 Caves are cut in dark grey basalt rocks.
	5.6 Cliffs of columnar basalt are bleached white because of the salt.
	5.7 Arches are eroded too. Only a few rocks are not black or grey.
	5.8 A stack appears black in the sunlight evidence of a lot of land being eroded by the stormy North Atlantic Ocean.
	5.9 This is one of the supplies of sediment to the coast.
	5.10 This is a sandur a vast plain of fine black or dark grey sediments criss-crossed by rivers. This holds the key to the black sands.
	5.11 Erosion of the largest single outpouring of lava in history from Katla in 1783 is black and crumbly in places. There are also vast areas of volcanic ash too.
Low - High	5.12 Did you know you are on a volcano here?
Low - High	5.12 Ride on a skidoo across an ice cap over a volcano. I know I know there is no sign of it -the movie
	5.12 The real story begins on top of an icecap which has the volcano, Katla beneath 100s of metres of ice.
	5.13 Glaciers flow from the ice caps down valleys.
	5.14 They grind away at the rocks beneath creating sediments from vast boulders to milky rock flour.
	5.15 Every so often the sub-glacial volcanic activity melts the ice in the glacier and a vast flood bursts out from under the glacier.
	5.16 These floods are called jokullhaups and they can bend metal girders and take away bridges and roads.
	5.17 These features happen only where there is volcanic activity and glaciers.
	5.18 These sediment plains are washed out to sea a combination of volcanic ash and rocks and the glacial sediments. You can see the plume in the sea.
	5.19 Making the beaches black when wet…
	5.20 and all shades of grey when drying.