A booming noise. A hefty rumble.
In the cold of winter, many across the north country and Ontario are reporting incidents nicknamed frostquakes, a figurative shuddering of the ground as it reacts to frozen moisture under its surface.
People think theyre earthquakes, but theyre not, said Frank A. Revetta, a geology professor at SUNY Potsdam.
The events, also known as cryoseisms, take place as the moisture enters into rocks. As temperatures drop, the moisture freezes and expands, creating a high level of pressure released with the cracking of the rocks.
Unlike actual earthquakes, the activity creates no damage, and is not a public safety threat.
Even to seasoned geologists such as Mr. Revetta, a lot of mystery surrounds the incidents, which can appear on seismographs but with much less activity than earthquakes.
Among the questions for researchers are what factors play a role in their activity, such as snow cover, and the types of rocks more affected by the temperature.
We really dont know that much about them, he said.
With a limited range of seismic activity, the frostquakes are tough to capture on seismographs for further research without some luck on location.
If its not close, youre not going to catch it, Mr. Revetta said.
One thing is constant, he said.
Its going to have to be very cold, so cold that the ground is freezing, the water in the ground is freezing, the lake is freezing, he said.
Mr. Revetta said that though he has seen small readings of the quakes on sensors he has placed around the region, he has never experienced one in person.
Id like to feel one, to see what theyre like, he said.
To those who have felt the shakes, the quakes bring concern, along with a healthy level of confusion.
For Megan J. Martin, her Christmas morning was disrupted at about 4 a.m. with the sound that she thought was a tree falling on her Redwood home. A lifelong resident of the village, she said she had never heard anything like it before.
It woke me out of my sleep, she said. I didnt know what it was. I thought it was Fort Drum.
In the morning, she searched for any signs of damage and found nothing. Confused about what had happened, she posted what she remembered on her Facebook page.
I started asking around, and everybody heard it, she said.
Over in LaFargeville, Jeffrey M. Leiendecker said he had heard noises around his home for the past few weeks, in line with the recent dive in temperatures.
However, he said nothing compared to the massive boom around 10:30 p.m. Friday night, which reverberated through his house and shook him from his couch.
I thought it was the heater exploding, it was that much of an explosive sound, he said.
Searching through his home and basement, he could find no damage to his home. He discovered the next day what he experienced was likely a frostquake.
Mr. Leiendecker, who works at the Jefferson County Public Health Department, said he had previous geologic work experience and a bachelors degree in geology, but that he had not encountered anything like the frostquakes. His past work experience was in Virginia and Hawaii, and he had only been in the north country since 1999.
Its not been cold enough to experience something like this, Mr. Leiendecker said.
In colder winters like this seasons, Mr. Revetta said he may get a handful of calls about incidents at peoples homes.
When theres a cold spell, people call, he said.
A large-scale frostquake incident was reported in Toronto early Friday, according to a report in the National Post. The report can be seen at http://wdt.me/BqAcoL.
This story has been updated to correctly list Mr. Leiendeckers educational background