Morning Glory Pool

Debris can clog the water supply, block or redirect runoff, or introduce chemicals and sediment into the system.

Morning Glory Pool is probably the best example.

It was named back in the 1880s because its brilliant blue color reminded people of a morning glory flower.

But over the years, visitors threw thousands of pounds of coins, rocks, logs, and other trash into it.

Some of that material became lodged in the spring and restricted the circulation of hot water.

That helped lower the temperature, allowing different heat-loving microorganisms to grow.

The result is that Morning Glory Pool no longer has the same pure blue appearance that it once had.

The National Park Service also notes that natural changes may have contributed to the cooling, so the entire color change isn't necessarily blamed on visitors alone.