Go Back
  • For Business
  • |
  • Warnings
  • Data Suite
  • Newsletters
  • Advertising
  • Superior Accuracy™
Father's Day forecast: See where thunderstorms could impact outdoor plans. Chevron right

Ashburn, VA

85°F
Location Chevron down
Location News Videos
Use Current Location
Recent

Ashburn

Virginia

85°
No results found.
Try searching for a city, zip code or point of interest.
settings
Ashburn, VA Weather
Today WinterCast Local {stormName} Tracker Hourly Daily Radar MinuteCast Monthly Air Quality Health & Activities

Around the Globe

Hurricane Tracker

Severe Weather

Radar & Maps

News

News & Features

Astronomy

Business

Climate

Health

Recreation

Sports

Travel

For Business

Warnings

Data Suite

Newsletters

Advertising

Superior Accuracy™

Video

Winter Center

AccuWeather Early Hurricane Center Top Stories Trending Today Astronomy Heat Climate Health Recreation In Memoriam Case Studies Blogs & Webinars

News / Weather News

July was a 'doozy' of a month for Earthquake Country

By Adriana Navarro, AccuWeather staff writer

Updated Aug 5, 2021 4:17 PM EDT

Copied

A collection of quakes that occurred during July 2021. (USGS)

The U.S. Geological Survey's (USGS) Yellowstone Volcano Observatory clocked over 1,000 quakes during the entirety of July, and seismologists say most of these have roots not in magma but in water.

In its monthly update, the observatory's scientists reported that at least 1,008 earthquakes occurred in the national park during the entirety of July -- the most quakes recorded in Yellowstone since June 2017 when officials recorded over 1,100 events.

"It was a doozy of a month for earthquakes in Yellowstone during July," Michael Poland, USGS geophysicist and Scientist-in-Charge at the Yellowstone Volcano Observatory, said in a monthly update video for the observatory.

#Yellowstone July update: “doozy” of a month for EQs (7 swarms, 1000+ EQs, largest a M3.6). Existing faults “goosed” by increased pore pressure (from snow melt) & not magma moving (no change in #deformation data). #DYK: Solitary geyser once fed a swimming pool near Old Faithful? pic.twitter.com/cgXTdGDY7T

— USGS Volcanoes🌋 (@USGSVolcanoes) August 2, 2021

The activity last month was clumped together in swarms, mostly consisting of 12 to 40 events, though one swarm under Yellowstone Lake totaled an impressive 764 quakes. The swarm kicked off on July 16, although it tapered off in activity during the following days.

This flurry of activity doesn't reflect magmatic activity in the "earthquake country," however.

"These earthquakes are not associated with magma movement as might be assumed because, of course, the word is out that Yellowstone is a volcanic structure," Poland told AccuWeather. "Yellowstone also has a tremendous amount of groundwater, and that's from all the snow that falls in that area. That's the highest area in the Rockies on average, and it's absolutely full of preexisting faults."

As the underground pore space soaks up the snowmelt-turned-groundwater, it increases pressure on those nearby faults and can even cause them to fail.

CLICK HERE FOR THE FREE ACCUWEATHER APP

"We typically see lots and lots of earthquakes when the snow melts or it gets into the ground and interacts with these faults," Poland said. "That's what caused earthquakes the last real big month for earthquakes back in June of 2017."

Over 2,400 earthquakes fired off in a swarm that lasted for three months starting back in June 2017, and that was just the park's second largest swarm. The largest swarm was another three-month event during 1985 that included over 3,000 earthquakes.

FILE - In this Oct. 8, 2018, file photo, Emigrant Peak is seen rising above the Paradise Valley and the Yellowstone River near Emigrant, Montana. (AP Photo/Matthew Brown, File)

While they come in multitudes, these kinds of quakes are relatively small compared to their magmatic counterparts. The largest earthquake from the 2017 flurry of events that lasted from June into September reached an M4.4. Last July, the largest was a M3.6 quake under Yellowstone Lake on July 16.

Usually, the strength of these earthquakes range from M1 to the occasional M4, meaning the lower-end ones might not be felt at all.

Scientists are able to separate the earthquakes associated with the snowmelt from those with magma by looking at the environment around the site.

"If these were volcanic quakes ... we would see other changes," Poland pointed out. "We would see different types of seismicity, different frequencies of shaking, and we would also see other changes, for example, ground deformation."

If magma was moving toward the surface, it would move rock out of the way and be reflected at the surface, he added. Other changes that would indicate magmatic activity would be changes of thermal emissions or gas emissions. The observatory noted not finding any of these indicators that could suggest the quakes were associated with magma.

Visitors are seen at Grand Prismatic Spring in Yellowstone National Park, Wyoming on May 1, 2021. (AP Photo/Iris Samuels)

These quakes can occur in areas other than Yellowstone as well, such as the Sierra Nevada, for example. And since snowmelt is a large part of the cause, there can be almost a seasonality to them.

"We can see earthquakes that are sort of seasonal in nature and that tie in with snowmelt and the recharge that that snowmelt gives to groundwater systems," Poland said. "Same thing happens say in the Cascades. Mount Hood often sees earthquakes and earthquake swarms that are occurring at about the time that all that seasonal snowmelt is really getting into the groundwater system."

It's currently unclear whether climate change and the changing snowpacks would have an impact on the frequency of these kinds of earthquakes, he added, noting that while there is a change in the amount of snow falling in Yellowstone, there's a delicate balance regarding if a fault was ready to fail.

Related:

Weather News Great Salt Lake in 'dire state' as Western drought worsens
Severe Weather Survivor recalls fateful day of deadly lightning strike

Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier, Spectrum, FuboTV, Philo, and Verizon Fios.

Report a Typo
Comments that don't add to the conversation may be automatically or manually removed by Facebook or AccuWeather. Profanity, personal attacks, and spam will not be tolerated.
Comments
Hide Comments

Weather News

Weather News

Wildfire smoke to limit number of days with deep blue sky this summer

Jun. 12, 2025
Weather Forecasts

More storms, temperature swings ahead for the Northeast

Jun. 13, 2025
Weather News

Children swept away among at least 49 killed in South Africa flooding

Jun. 11, 2025
Show more Show less Chevron down

Topics

AccuWeather Early

Hurricane Center

Top Stories

Trending Today

Astronomy

Heat

Climate

Health

Recreation

In Memoriam

Case Studies

Blogs & Webinars

Top Stories

Weather News

How the Air India plane came crashing to earth

1 day ago

Severe Weather

Severe storms to focus over Plains through Father's Day weekend

3 hours ago

Weather Forecasts

More storms, temperature swings ahead for the Northeast

3 hours ago

Weather Forecasts

Father’s Day forecast: West to have best weather for outdoor activitie...

6 hours ago

Weather News

At least 8 dead in San Antonio after months of rain fell in hours

3 hours ago

More Stories

Featured Stories

Climate

If crucial ocean currents collapses, weather impact would be extreme

2 days ago

Weather News

No injuries after JetBlue plane rolls onto grass after landing

1 day ago

Astronomy

Accidental find in planetarium could shift understanding of solar syst...

2 days ago

Climate

New Zealand sued over ‘inadequate’ plan to reduce emissions

2 days ago

Weather News

New images reveal treasures aboard ‘holy grail’ shipwreck

1 day ago

AccuWeather Weather News July was a 'doozy' of a month for Earthquake Country
Company
Proven Superior Accuracy About AccuWeather Digital Advertising Careers Press Contact Us
Products & Services
For Business For Partners For Advertising AccuWeather APIs AccuWeather Connect RealFeel® and RealFeel Shade™ Personal Weather Stations
Apps & Downloads
iPhone App Android App See all Apps & Downloads
Subscription Services
AccuWeather Premium AccuWeather Professional
More
AccuWeather Ready Business Health Hurricane Leisure and Recreation Severe Weather Space and Astronomy Sports Travel Weather News Winter Center
Company
Proven Superior Accuracy About AccuWeather Digital Advertising Careers Press Contact Us
Products & Services
For Business For Partners For Advertising AccuWeather APIs AccuWeather Connect RealFeel® and RealFeel Shade™ Personal Weather Stations
Apps & Downloads
iPhone App Android App See all Apps & Downloads
Subscription Services
AccuWeather Premium AccuWeather Professional
More
AccuWeather Ready Business Health Hurricane Leisure and Recreation Severe Weather Space and Astronomy Sports Travel Weather News Winter Center
© 2025 AccuWeather, Inc. "AccuWeather" and sun design are registered trademarks of AccuWeather, Inc. All Rights Reserved.
Terms of Use | Privacy Policy | Cookie Policy | About Your Privacy Do Not Sell or Share My Personal Information

...

...

...