At a Glance

The new thermal area has been forming over the past two decades.It was first spotted on infrared images of the existing Tern Lake thermal area. Scientists say it's just a normal part of Yellowstone's dynamic hydrothermal activity.

Yellowstone National Park has a new thermal area that scientists think has been growing for the past 20 years.

The new area is between West Tern Lake and the previously mapped Tern Lake thermal area, the U.S. Geological Survey announced earlier this month.

"This is from Yellowstone's dynamic hydrothermal activity," R. Greg Vaughan, a research scientist with USGS, wrote in a blog post, "and it highlights that changes are always taking place, sometimes in remote and generally inaccessible areas of the park."

A thermal area is the visible result on the Earth's surface of magma activity underground. They can include geysers, like ; hot springs; and fumaroles, which are vents that allow volcanic gases to escape. They are surrounded by hydrothermal mineral deposits, geothermal gas emissions, heated ground and lack of vegetation, the USGS says.

This map shows thermal areas in Yellowstone National Park. The orange box shows the location of the Tern Lake thermal area.

(USGS)

Yellowstone has about 10,000 thermal areas concentrated into about 120 distinct areas.

The new thermal area, about half a mile from the nearest trail, and about 11 miles from the nearest trailhead, was first noticed in an infrared satellite image acquired in April 2017. The area showed up as a bright spot between the Tern Lake thermal area and the western edge of West Tern Lake.

High-resolution aerial images later confirmed a large area of dead trees and bright soil, USGS said, the type of scene expected over a thermal area.

Historical images showed the area began forming in the late 1990s or early 2000s. Those images also showed that the Tern Lake Thermal Area had grown on its northern side.

Aerial images of the Tern Lake area from 1994, 2006 and 2017 show the emergence of the new thermal area.

(USGS)

"Yellowstone's thermal areas are the surface expression of the deeper magmatic system, and they are always changing," Vaughn wrote. "They heat up, they cool down, and they can move around."

A recent example was the eruption of the . The eruption this past September sent water and steam 20 to 30 feet in the air. Several other thermal features formed at the same time.

Any geological changes at Yellowstone tend to make headlines because the park sits atop an underground supervolcano that is 44 miles across and last erupted more than 630,000 years ago. However, scientists with the say there is nothing to worry about.

(WATCH: Why Yellowstone Supervolcano is So Powerful and Scary)

"We've heard many statements that Yellowstone is overdue — that it has a major eruption every 600,000 years on average, and since the last eruption was 631,000 years ago... well... ," Michael Poland, scientist-in-charge of the Yellowstone Volcano Observatory, recently wrote in a blog post. "Is this true? In a word, no. In two words, no way. In three words, not even close. Yellowstone doesn't work that way."