Colorado isn't exactly known for its volcanic activity, but there are four volcanoes in the state you can visit.

According to the Colorado Geological Survey, there was a time when two-thirds of Colorado's land area was covered by volcanic rock, and now much of it has eroded away.

It's believed that Colorado was a bed of volcanic activity between 25 million and 37 million years ago. While you can find volcanic rock throughout Colorado, the largest concentration is in the southwest region.

Here are four volcanoes in Colorado for geology and hiking enthusiasts to check out.

1.  DOTSERO

The Dotsero Volcano is considered to be an active volcano, though we certainly aren't expecting any eruptions in the near future. The most recent eruption is believed to have occurred just over 4000 years ago.

To get there, take I-70 to Exit 133, drive a half mile on Colorado River Road to the trailhead. The hike is about three miles one way.

2. North Table Mountain

The lava flows on North Table Mountain are believe to be 62-64 million years old. Several new trails have been constructed and it's a popular hiking and recreational destination on the front range.

To get there, take Highway 93 north of Golden to the North Table Mountain parking lot. It's a round-trip hike of 3.2 miles.

3. La Garita Wilderness Area

The Wheeler Geologic Area in the La Garita Mountains was Colorado's first national monument.The layers of volcanic ash are from the La Garita Caldera, one of the largest volcanic eruptions in the Earth's history.

To get there travel 10 miles north, north-east of Creede. The road to the geologic formations requires a solid 4x4 or ATV. The other option is a seven-mile hike.

4. Goemmer Butte

The butte is considered by some to be a "volcanic plug."  This is where magma vents to the surface of the Earth and existing rock is broken, mixed, and dislodged by violent high-pressure gas/steam explosions.

To get there take highway 12 for 20 miles past La Veta. Go east on Forest Road 46 and go 6 miles to the summit of Cordova Pass and the trailhead. There is an 8-mile roundtrip loop to the top of West Spanish Peak.