Modern day volcanoes, i.e. the last few thousand years seem to be responsible for noticable cooling effects on the climate, i.e. Mount Pinatoba, Tambora etc.  This is i assume is down to dust, ash and sulphur dioxide been spewed into the air and reflecting incoming solar radiation.

 Although it seems volcanism in earths geological history appear to be responsible for notable warming events, attributed to greenhouse gas emmisions.  I know the residence time of greenhouse gasses are usualy longer than ash, dust and sulphur aerosols, however continued eruptions i would imagine would keep a constant supply of sulphur in the atmosphere thus cooling the planet.

Please explain this contradiction.

Thanks

Mark

The UK, Ireland, Norway, North and South America, New Zealand etc. all have most of their mountains and glacial "jagged "coastline on their west.  Eastern coastlines seem to be generally much "smoother" and generally less hilly.

What is the reason for this and are there any exceptions?

I first found one of these blue-grey stones on a beach in Northumberland 5 years ago. Since then I have found more than 20. They have a very regular skew triangular prismatic shape and they are all the same size. They measure about 20mm along every edge. They are very hard and can scratch glass. I can't see how they could have formed naturally as they are all of such similar size and shape. If they are man-made, however, what are they for? I have only found then on one beach, which is about 30m in length and south of a reasonably active harbour (Seahouses).