Geiseres de Puchuldiza EarthCache

Andean volcanism - the source for geothermal activity in northern Chile

In northern Chile, the volcanism emplaces along the High Andes and part of the Altiplano block. The Andean Cordillera rises along the South American subduction zone. A subduction zone is an area on Earth where two tectonic plates move towards one another and subduction occurs. This process involves an oceanic plate sliding beneath either a continental plate or another oceanic plate. Subduction zones are often noted for their high rates of volcanism, earthquakes, and mountain building. 

The volcanic rocks of the Andean Cordillera include ash-flow tuffs and lavas erupted from calderas and volcanoes that crown the highest summits of the Andes. Although volcanic activity has been intense during the Quaternary, spanning ~ 2500 million years ago to the present, only a few volcanoes such as Isluga, San Pedro, Lascar and Llullaillaco, have remained active until present. Many others show occasional to permanent hydrothermal activity. Volcanic vents and hydrothermal manifestations occur associated with small grabens connected with fault systems formed due to tectonic uplift of the Andes (eg. El Tatio and Puchuldiza geothermal fields).

The South American subduction zone

model of the origin of geothermal activity

The origin of geothermal activity

As mentioned above, volcanism is often related to geothermal activities, such as fumaroles, hot springs or geysers.

In the high mountains, water falls as snow or rain and slowly percolates through layers of porous rock, finding its way through cracks and fissures in the earth's crust. Sinking to a depth of nearly 10,000 feet, this cold water comes into contact with the hot rocks associated with the shallow magma chamber beneath the surface. As the water is heated, its temperatures rise well above the boiling point to become superheated. The highly energized water is less dense than the colder, heavier water sinking around it. This creates convection currents that allow the lighter, superheated water to begin its slow journey back toward the surface, following the cracks, fissures, and weak areas of the earth's crust. The release of water at the surface prompts a sudden decline in pressure of the hotter waters at great depth, triggering tremendous steam explosions in which the volume of rising, now boiling, water expands 1,500 times or more. This expanding body of boiling superheated water bursts as a geyser. If released in a slow steady manner, the water gives rise to a hot spring. If the water reaches the surface in the form of steam, it is called a fumarole.

There are hot springs all over the earth, on every continent and even under the oceans and seas. There is no universally accepted definition of a hot spring. But a very common definition is that a hot spring is a spring with water temperatures of more than 8°C above its surroundings.

The use of geothermal energy

Hot springs have been used for bathing since Paleolithic times, 2.5 million years ago - 12,000 BC. The oldest known spa is a stone pool in China built in the 3rd century BC. In the first century AD, Romans conquered Aquae Sulia, the town today known as Bath in Great Britain and used the hot springs there to feed public baths and underfloor heating.Today, geothermal energy is now better known for generating electricity.Worldwide, geothermal plants have the capacity to supply about 0.3% of global electricity demand. Geothermal power is cost effective, reliable, sustainable, and environmentally friendly. Drilling and exploration for deep resources costs tens of millions of dollars, and success is not guaranteed.

Interest in geothermal energy in Chile dates back to the beginning of the 20th century. At that time (1908), members of the Italian colony at the city of Antofagasta created a private society named Preliminary Community of El Tatio. This society carried out the first geothermal exploration program in the country. Systematic exploration in the northernmost region of the country resumed by the end of 1968 as result of a project subscribed by the Chilean Development Corporation (CORFO) and the United Nations (UNDP). Geological and geochemical reconnaissance of many hot-spring areas and detailed geological, geophysical and geochemical surveys in selected areas such as Surire, Puchuldiza and El Tatio geothermal fields, were performed during the period 1968-1976. These endeavors were followed by drilling of a number of exploratory wells down to ~ 1000 m depth and feasibility studies for power generation at El Tatio and Puchuldiza. By early 2000, a Geothermal Law was enacted providing the framework for the exploration and development of geothermal energy in Chile. The law establishes the existence of exploration and exploitation concessions. Based on geological and geochemical reconnaissance of many hot spring areas, several areas were selected as promising for electrical applications.

geothermal fields and volcanoes in northern Chile

The geothermal field of Puchuldiza

Puchuldiza is one of the highest geothermal field in the world. The field is located in the Western Andes at 4200 m height and covers an area of ~ 90 km². The climate is typical for a high mountain range like the Andean Cordillera. The temperatures vary between 15°C at day time and -15°C at night. It is usually very dry with just ~ 100 mm/ m² of rain fall. Just in january and february, when the Bolivian Winter is hitting the mountain range, heavy rain falls and inundations are likely to happen. The geothermal field is surrounded by some of highest mountains of the region, in the south the Cerro Guaillane (4952 m) and the Cerro Condoriri (4894 m) and to the north the Cerro Latarani (5207 m) and the Cerro Macurquima (5119 m). Thermal activity is grouped into two main thermal areas, Puchuldiza and Tuja. The latter is the smallest thermal focus lying about 5 km from Puchuldiza. The hot springs are based on a terace of sinter and salt. The water supply is coming from a drainage network arising in the northern part and is leaving the field by the river of Puchuldiza to the north west to the geothermal field of Tuja. Most of the almost one hundred springs found in this area are emerging at a temperature between 40 - 89°C, the boiling temperature at this height of 4200 m. Chemical geothermometry studies suggest reservoir temperatures in the range of 180°C at 100 - 500 m depth and more than 250°C at deeper layers. Due to the high amount of hot springs, Puchuldiza is of high geothermal potential. Analysis of the deeper layers of the area suggest a size of 28 km² for the geothermal water reservoir.

the area of Puchuldiza and Tuja ...

... with two geological profiles

The Earth Cache

Before visiting Puchuldiza, read the following points carefully, please:

• This is a remote area, so don't go there alone.

• Make sure you have an appropriate vehicle to reach the geothermal field. The road is paved apart of the last ~ 12 km. For the last part you will have to drive on a gravel path, which is well maintained but not paved.

• You are going up to a height of ~ 4200 m. Bring enough water (2 l per pers.) and be aware of any sign of mountain sickness. In case you feel anything like headache or nausea immediately leave the height to a lower place.

• Once you arrive at Puchuldiza be aware that the soil of the geothermal field can be very thin and hot. Even if you don't see it, the delicate underground close to the hot springs might break - so watch your steps! I recommend to leave the car at the entrance and walk around the field since distances are not far. If you want to drive, don't leave the paths to avoid contact with the hot springs.

• The water of the hot springs is really hot or even boiling so be very careful when approaching a pool. The activity of the springs can increase rapidly even if it appears to be calm.

• Enjoy your trip to Puchuldiza and don't forget your camera! The area up there is absolutely amazing!

Access

Take the Ruta 5 to Huara and from there, follow the Ruta 15 to the North East. After 75 km you will reach the thermal springs of Chizmisa. Follow the road for some 55 km more and you will reach the gravel road to Mauque direction to the north. After ~ 10 km you will see the official sign to the "Thermas de Puchuldiza". Just follow the road for another ~ 10 km and you will reach the geothermal field.

Logging the Earth Cache

To log the Earth Cache as found, I have prepared three small tasks for you. They are all voluntary and will not effect your log of the cache. But you will learn more about the geothermal field fulfilling them. Mail the answers to my account and upload the picture.

(1) Go to the hot spring close to the entrance. What is the estimated diameter of this spring?

(2) Visit the geyser of Puchuldiza. What is the estimated height of the fountain?

(3) Of course, you should take a bath at the pool of Puchuldiza! Take a picture of you in the pool and post it :-)