Every year about this time, we see headlines of "Earthquake Swarms In Yellowstone National Park." Why do they happen? Why do they happen each year at this time?

There is a scientific reason.

According to IFL Science, researchers believe swarms of quakes in and around Yellowstone National Park are in part due to the release of pressure as snow melts.

"The Yellowstone Volcano Observatory, US Geological Survey (USGS) seismologist David Shelley says that the patterns of this swarm suggests that the earthquakes were likely caused by water diffusing through cracks in the Earth’s subsurface and not the movement of magma (although that can sometimes generate earthquake swarms at volcanic sites)."

According to the website Live Science: ...while the swarm is bigger than the everyday seismicity in the park, it's not a sign of a major quake, said Michael Poland, scientist-in-charge of the USGS Yellowstone Volcano Observatory in Vancouver, Washington. "This is what Yellowstone does; this is Yellowstone being Yellowstone," Poland told Live Science. "It experiences swarms all the time."

The swarms don't all peak in the spring. They can happen later in summer too. Rest assured this is not a sign of "The Big One." If anything these little quakes release pressure, which is good.