Informational Passage

7th grade reading level

Yellowstone: Old Faithful and the Hotspot

Yellowstone National Park is a strange and unique area. The park mostly falls within the western state of Wyoming. However, small parts of it are in Montana and Idaho.

Yellowstone sits in the mouth of a super volcano. It has features such as the Old Faithful geyser, natural hot springs, and boiling mud pots that smell like rotten eggs. That all exists because of something called a hotspot.

Geologists say hotspots are places deep underground that don’t move. No one knows why, but they contain superheated magma from deeper in the earth.

The surface of the earth is made of something called tectonic plates—huge slabs of rock that fit together like a big puzzle. Over time, the plates very slowly shift and move. Geologists can track the movement with special instruments.

The hotspot that created Yellowstone used to be under the Pacific Ocean. So, how did it get to Wyoming? Because the North American plate has been inching father west for millions of years. Eventually, it moved over the top of the hotspot. That heated up the plate and caused things like volcanos and geysers.

The hotspot has left a trail of now-inactive geological features from the west coast to Yellowstone. This includes the Craters of the Moon National Monument in Idaho, which looks like the moon.

The hotspot causes all of Yellowstone’s odd features, including Old Faithful. The famous geyser got its name because it’s predictable. Its eruptions are between 35 minutes and two hours apart. Special equipment can predict the next one.

Old Faithful isn’t as faithful as it used to be, though. Scientists say it’s erupting a little less often. They believe that’s because the plate has shifted just slightly. Even so, the geyser shoots boiling water between 90 feet and 180 feet into the air many times a day.

Over time, the North American plate will shift far enough that Yellowstone will no longer be geologically active. Experts say the hotspot will eventually be under South Dakota or Iowa. At a rate of about 3 centimeters a year, though, it’ll take millions of years to get there.