How does an eruption of the Geysir Andernach work?

Learn. Marvel. Understand.

Dividing line

With an eruption height of up to 60 m, the Geysir Andernach is the highest cold-water geyser in the world. It is located directly on the Rhine about 2 km downstream from the town of Andernach on the Namedyer Werth peninsula. Only here are the geological conditions necessary for the Andernach geyser.

In the course of the last 300 to 400 million years, large geological faults formed as a result of mountain-building processes, which intersect under the Namedyer Werth. Areas where rock packages several thousand metres thick have shifted against each other. This resulted in cracks, crevices, fissures that reach deep into the earth's interior.

Carbon dioxide (CO2) rises through these so-called pathways. TheCO2 comes from the magma deep beneath the Eifel, Germany's youngest volcanic area.
On its way towards the earth's surface, theCO2 encounters groundwater and dissolves in it. The resulting gas-water mixture flows to the geyser well at several depths.
Unlike hot-water geysers, all cold-water geysers require an artificial connection from the earth's surface to the depths, i.e. a borehole or well. The well of the Andernach geyser is a good 350 m deep.

Phase 1 to 4

Dividing line

The groundwater saturated withCO2 flows into an empty well. There, the (water) pressure is low. This means that the gas can/must dissolve out of the water. It escapes from the well, which can be perceived by a smallcloud of CO2 above the well opening. The air flickers.
As the water column in the well rises higher and higher, the water pressure increases. When the well is completely filled, it is 35 bar at a depth of 350 metres. This means that a large amount ofCO2 is dissolved in the 20 to 25° Celsius cold water; the gas is virtually invisible in the water. The gas cloud above the well opening has disappeared.

Phase 5 to 8

Dividing line

Shortly after the well is full, the geyser eruption phase begins: theCO2 cannot dissolve any further in the water, saturation is reached. Gas bubbles form and rise in the well. As they rise, the speed and volume of the bubbles increase. TheCO2 bubbles need space and displace water to the surface. The well overflows. As a result, the pressure of the water or the gas-water column in the well decreases. Gas that was previously dissolved in the water is released and displaces more water to the earth's surface. A domino effect sets in. The geyser fountain gets higher and higher.

Phase 9

Dividing line

The main phase of the geyser eruption is reached when more and more gas is released from the water and the gas bubbles join together to form larger and larger bubbles on their way up. The small diameter of the well pipe of only 15 cm causes the bubbles to expand primarily vertically. This creates 10 to 15 m long so-called piston bubbles. These tear and pull a total of about 8,000 litres of water upwards and hurl it pulsatingly out of the geyser well up to a height of 60 metres. Gradually the fountain empties, the fountain becomes smaller and smaller and finally disappears completely. The entire geyser eruption takes about 15 minutes.

Phase 10

Dividing line

CO2-saturated groundwater flows into the now empty well. The gas dissolves out of the water, the flickering above the well opening can be seen again. 110 to 120 minutes later, the time has come: the well is full, the next geyser eruption begins...

Nature Geyser Background

Customer testimonials

Your opinions & experiences

Dividing line

Nice excursion with a nice explanation. We had a very nice trip to the geyser. The geyser was very impressive to see. Special thanks to the staff, who were very friendly and helpful, and thus made the excursion possible for us (help due to walking disability).  

Customer testimonial from

Absolutely recommendable! In an interactive tour, you can learn about the formation of a geyser in a playful way. The absolute highlight is the boat trip to the geyser, where you can see the natural spectacle live.

Facebook Customer testimonial from

We were there with the whole family, grandparents, parents and children! There was something for everyone and it was very interesting! Just a super great day spent with the whole family!

Facebook Customer testimonial from

It is a wonderful hands-on museum. Even small children can try things out and explore here. Older children and adults learn a lot of new things. The accompanying boat trip is a highlight. The geyser experience at the end is just great. The staff are polite and nice. Very helpful. The museum is also suitable for prams. Parking is scarce, but with a bit of luck you can get to the...

Customer testimonial from

The boat trip to the geyser was informative and you were told how the geyser was formed. There was a lot of staff on site who were happy to share their knowledge. Talking to the staff was very helpful and informative.

Customer testimonial from

Thank you very much! 2022 season ends with 110,000 visitors

After 219 days of operation, the 2022 season ends at the geyser. In the past months, a total of 110,000 visitors were welcomed to the facility. On 26.03.2023 we start again in the new season. By phone we are still available for you under the telephone number 02632 - 958008 0 or by mail

We look forward to seeing you in 2023.

Your Geyser Team

Winter break Geyser Andernach