How Can One Volcano Change the World?
ESU301  Ongoing Danger
M.T. Dolan, University of Michigan
This lahar filled an existing valley after the eruption. Now, its surface is eroding away, supplying ash to new lahars whenever it rains.

The danger from lahars around Mount Pinatubo didn't end when the eruptions did. Ash deposits are eventually covered by vegetation and compacted into rock. However, while the ash is loose, it can be remobilized and move downhill every time it rains. The lowland areas surrounding Mount Pinatubo remained vulnerable to deadly lahars sweeping down mountain valleys for years after the eruption.

In an attempt to keep lahars from overflowing riverbanks and covering cities and farmlands, earthen dikes were built along some riverbeds. These efforts to save land and homes weren't always effective, however. Large areas of farmland were covered by lahars and can no longer be farmed.

6. Which spheres interact to form lahars? Describe the interactions that result in lahars.


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