Book 12, Question 106
Why Do Ash Samples Get Studied Under Microscopes?
Scientists study ash under microscopes because volcanic ash is made of tiny pieces of broken glass and crystal. The shapes and kinds of pieces tell the story of the eruption. A pinch of ash can teach a lot.
More fun facts
- In a sample bag, volcanic ash looks like specks of dust, but under magnification the grains turn out to be rough, glassy shards.
- Ash from explosions powered by expanding volcanic gas looks like tiny pieces of frozen foam with broken bubble walls.
- Ash from explosions where hot magma met liquid water looks like broken glass: dense and blocky.
- Scientists first spotted this difference in the 1970s using big, expensive electron microscopes to look at just a few grains.
- A newer grain shape analyzer pumps ash through water-filled tubes past a camera that snaps 30 pictures every second.
- With that machine, one scientist plotted the shapes of 20,000 ash grains at once.
- The grains turned out to form a whole range, from bubble-free blocky shards to very foamy grains, which helps show how much water was involved.
- One slice of Icelandic soil holds 800 years of ash layers from five different volcanoes, including black layers 5 to 10 centimeters thick from Katla Volcano.
Sources: U.S. Geological Survey
Questions kids ask
What can a single ash grain tell scientists?
Its shape hints at what caused the explosion, such as expanding gas or magma hitting water.
How small are ash grains?
Some grains scientists study are only about 150 microns across, which is about 0.006 inch.