Geysers

 

One of the highlights of a trip to Yellowstone is it's geysers.  A geyser is a result of water draining down a long tube into the earth to a volcanic zone.  Once it heats up enough, it comes shooting back out and many feet into the air.  This process repeats mostly at regular intervals.   Old Faithful erupts about 20 times a day.  Yellowstone is the largest geyser locale on the planet containing about half of the world's geysers.  I have also seen a few geysers in Iceland.  

Here is a sampling of what is at Yellowstone.

This one was very close to the boardwalk, and people were getting wet!

A mini geyser near Old Faithful.  This one went off every 5-10 minutes.