Yellowstone National Park was shaking a little more than normal during the month of July, with 1,008 earthquakes. A report this week from the U.S. Geological Survey noted "the most energetic swarm of earthquakes in the region since the Maple Creek earthquake swarm" from June to September in 2017, when 1,100 earthquakes were recorded. This past month's total was above average for the park, but USGS said it was "not unprecedented." The current volcano alert level remains "Green," or normal, as of August 2nd.

And seismologists said the small quakes were not caused by moving magma. There would be other indicators if magma was involved, including heat and gas venting, which was not detected. Instead, it was probably because of groundwater moving along pre-existing faults, which happens when groundwater increases after winter snow melts.

On July 16, a swarm of over 700 earthquakes started under Yellowstone Lake. The largest was magnitude 3.6 on the richter scale, but the rest were below that and the swarm had diminished to only a few per day into August. Six other swarms were located in the Old Faithful and West Yellowstone areas. From the USGS report: "Earthquake sequences like these are common and account for roughly 50 percent of the total seismicity in the Yellowstone region."

USGS also noted that Steamboat Geyser in the Norris Geyser Basin erupted only once during July. Steamboat, the highest geyser in the world, was sporadic until March of 2018, when it suddenly became more active. Two years later, it had erupted over 100 times. But now in 2021, it is sporadic again, erupting only 13 times so far, indicating that its frequent eruption period might be ending.

The earthquakes were detected by the University of Utah Seismograph Stations. The Yellowstone Volcano Observatory is one of five USGS Volcano Observatories in the United States.

LOOK: Stunning vintage photos capture the beauty of America's national parks

Today these parks are located throughout the country in 25 states and the U.S. Virgin Islands. The land encompassing them was either purchased or donated, though much of it had been inhabited by native people for thousands of years before the founding of the United States. These areas are protected and revered as educational resources about the natural world, and as spaces for exploration.

Keep scrolling for 50 vintage photos that show the beauty of America's national parks.