Re: Why does volcanic ash look like ash from things that were once alive?

Dear Mr. Fine and students,

Geologists call volcanic ash "ash" because it looks so similar to ashes 
found in fireplaces and barbeques.  However, volcanic ash is indeed very 
different!  

How are they different??

1) Well, it sounds like you may already know this, but volcanic ash is made 
of tiny pieces of rock. Volcanic ash forms when a volcano erupts 
explosively.  The explosion is similar to quickly opening a warm bottle of 
soda.  Droplets of lava and gases shoot out in every direction just like 
the soda and bubbles do (but the lava droplets are much, much smaller). The 
droplets of lava cool very quickly as they fly through the air, solidifying 
into tiny pieces of rock.  Remember, when a liquid cools to form a solid, 
we call that the process of freezing. So, lava freezes to form rock!


2) Volcanic ash is not the byproduct of a used fuel. Lava does glow red and 
yellow, appearing to be on fire, but it is not.  It glows because it is so 
hot, approximately 1,472 degrees Fahrenheit!  Keep in mind that something 
can be very hot, like pizza baking in a 500 degree oven, but it is not on 
fire.


3) On the chemical level, ashes from a fire are mostly made of carbon.  
Volcanic ash is made of the minerals feldspar and quartz and contain no 
carbon.  

4) Here is an activity to show how they are different in one other way:
 Compare the weight of a teaspoon of regular ashes to a teaspoon of 
volcanic ash.  Which one weighs more and why do you think so? (You could 
also do this comparison with a charcoal briquet and a similar sized piece 
of rock.)


I thank your students for a terrific question - Keep up the curiosity! If 
you need more info on this feel free to contact me. 

Ch