volcanic ashgreenspun.com : LUSENET : Introductory Geology, Oswego State : One Thread
Why was the volcanic ash(in class on the slide)white when the cloud was grey?
-- kelly cleason (firstname.lastname@example.org), February 25, 2001
I think the simple reason for this is becuase the volcanic ash had already settled and was spread out over a laorger surface area, where as the cloud was still thick, dense and compact giving it a darker color than the spread out ash.
-- Joel Bouchard (email@example.com), March 13, 2001.
If you look on page 95 of our book, under Volcanic Ejecta, it discusses how volcanic has the tendency to cool off while in the air. I agree with the other answer posted, which says that as the ash spreads out it takes on a lighter tone. However another explanation could also be that when the ash first comes out of the volcano it has a darker color, and as it cools (and moves apart like the other answer stated)it becomes lighter.
-- Sarah Szczech (firstname.lastname@example.org), March 13, 2001.
My answer is not scientific but rather based on some thought of how light and shadow work in nature. I think that the ash appears grey in the sky because it is blocking the light above it coming from the atmosphere above, we see the bottom of the ash and it appears as in a shadow therefore darker. In the class room enviornment we have one peice of ash and it in static infront of us now hovering abouve us in a cloud, we have an oppurtunity to see it in good light.
-- Mei-Ling Chen (email@example.com), March 29, 2001.