Pumice is made near the top of a volcano, at a vent where gases are being injected into the magma. It's so fragile and light, it will float in water - just like the dozens of pumice deposits you can find in the river valleys near Glacier Peak volcano. But on the east side? The same pumice deposits were violently ejected during an eruption some 13,000 years ago. Find out what we can learn from the evidence of past eruptions at Glacier Peak on the latest episode of Nick on the Rocks, now streaming