Jun 25 Reblogged
Icebergs sometimes have stripes, formed by layers of ice deposited on different conditions. Blue stripes are created when a crevice in the ice sheet fills up with melted water and freezes so quickly that no bubbles form. Green stripes form when an iceberg falls into the sea and a layer of water rich in algae freezes onto the bottom. Brown, black and yellow lines are caused by sediment, picked up when the ice sheet grinds downhill towards the sea.
(Photos: Antarctica Series by Steve Nicol)
Diatoms are generally the most important primary producers of marine and freshwaters. By absorbing CO2 in the production of organic material during photosynthesis they play a decisive role in the global carbon cycle. The complex, species-specific pattern in the structure of the cell-wall, composed chiefly of silica, can be extremely beautiful. Following death of the alga, the empty cell wall may be deposited in the sediments of lakes and oceans and be preserved as a valuable record about past environments and climate changes; as such they are important fossils for the reconstruction of millions of years of the Earth’s history.