Cerro Panizos facts for kids

Quick facts for kids Cerro Panizos
The lava domes in the centre of the image form the Panizos centre
Geography
Parent range	Cordillera de Lípez
Geology
Volcanic arc/belt	Altiplano-Puna volcanic complex
Last eruption	6.1 mya

Panizos is a huge, ancient caldera (a large volcanic crater) located in the Andes mountains. It sits on the border between Bolivia and Argentina. Panizos is part of a big group of volcanoes called the Altiplano-Puna volcanic complex. This area is known for having many active volcanoes.

Panizos was formed when the Nazca Plate (an oceanic plate) slid under the South American Plate (a continental plate). This process is called subduction. The volcano mainly produced a type of magma called dacite. The last time Panizos was active was about 6.1 million years ago.

The volcano is mostly hidden under a wide, flat shield of volcanic rock. This shield is about 40 kilometers (25 miles) across. Some of its highest points are over 5,000 meters (16,400 feet) tall. Scientists call it an "ignimbrite shield" because it's made of a rock called ignimbrite.

What is Panizos Like?

Panizos is a large volcanic shield made of ignimbrites. It's located right on the border between Argentina and Bolivia. Studying this part of the Andes is hard because it's so remote. But the ignimbrite rock from Panizos is easy to see and hasn't changed much over time.

Where is Panizos Located?

Panizos is part of the Central Volcanic Zone (CVZ) of the Andes. This is a long chain of volcanoes stretching from Peru to Chile and Argentina. About 50 volcanoes in this area have been active recently. The Altiplano-Puna volcanic complex is a huge area within the CVZ. It covers about 50,000 square kilometers (19,300 square miles). Other large calderas like Cerro Guacha and La Pacana are also found here.

How is Panizos Shaped?

At the center of Panizos, there's a group of lava domes. These domes are made of dacite rock and are about 10 to 15 kilometers (6 to 9 miles) wide. They might have formed during one big eruption or several smaller ones. These domes create a ring shape, which could be the edge of a collapsed caldera. This inner caldera is about 15 kilometers (9 miles) wide.

The entire complex is surrounded by a larger shield, about 40 kilometers (25 miles) wide. This shield is made of ignimbrites and has gentle slopes. There are also three flat areas made of lava, named Cerro Chinchinjaran, Cerro Tucunquis, and Cerro Anta Quevas. The whole Panizos complex covers an area of about 7,000 square kilometers (2,700 square miles). Its highest peaks, like Limitayoc and Panizos, are over 5,000 meters (16,400 feet) high.

How Panizos Formed

The volcanoes in this region, including Panizos, were formed by the Nazca plate sliding under the South American plate. This process creates magma deep underground. Panizos is located about 150 kilometers (93 miles) east of the main chain of volcanoes. Most of the volcanoes in this area produce large amounts of silicic (silica-rich) volcanic rock.

Panizos is also part of the "Tin belt." This area in the Andes has large deposits of tin minerals. These minerals formed from reactions involving the many volcanoes in the region. The magma that formed Panizos was changed a lot by interacting with the Earth's crust. The crust here is very thick, about 70 kilometers (43 miles) deep.

Scientists believe that volcanic activity in this area started over 10 million years ago. Around 12 to 10 million years ago, changes in the subduction process caused the crust to get thicker. This created areas where rock melted deep inside the Earth. Since then, this melted rock has risen to the surface, forming magma chambers and calderas like Panizos.

Rocks Around Panizos

The ground beneath Panizos is made of two main layers. The first is a sedimentary layer called Acoite, formed long ago. The second is a volcanic layer called Peña Colorada. It contains breccia, lava flows, and sandstone. Some of these rocks are about a billion years old.

Panizos is one of several large calderas in the Lipez region. Other huge calderas here include Cerro Guacha and Vilama. These areas have both arc and back-arc volcanism, meaning volcanoes form both directly above the subduction zone and further behind it.

What is Panizos Made Of?

Most of the rock from Panizos is dacite. There are also some andesitic rocks, mostly lava flows. The rocks from Panizos are rich in alumina and potassium. They contain about 61–66% silica.

Scientists study the chemical makeup of these rocks. For example, they look at isotopes of elements like Strontium and Lead. These studies show that the magma that formed Panizos mixed a lot with the Earth's crust. This mixing happened when hot magma from deep in the Earth rose and melted parts of the crust.

A cool feature of Panizos rocks are "orbs." These are rocks with layers of volcanic material wrapped around a central core. They are very rare in erupted lavas. In Panizos, these orbs are found in the lower part of the ignimbrite layer. They likely formed when magma temperatures changed quickly just before the eruption.

Climate Around Panizos

Panizos has a very dry climate. However, you can still see signs of water erosion from streams. Several stream valleys are found around the volcano, like Quebrada Cienago and Quebrada Cusi Cusi. The erosion is especially clear on the Argentine side.

Studies of other volcanoes in the area suggest that this region has been dry for a very long time, throughout the period of volcanic activity.

When Did Panizos Erupt?

Panizos had two main ignimbrite eruptions. It also produced several lava flows. All this activity happened in the Late Miocene period. The main Panizos ignimbrite sits on top of three older ignimbrite layers. These older layers are dated to about 9.7, 8.49, and 9.4 million years ago.

The first recorded ignimbrite in the area is called the Quebrada Cienago ignimbrite. It erupted about 7.9 million years ago. After this, dacite lava flows continued to erupt.

The main Panizos ignimbrite erupted about 6.71 million years ago. This was a complex eruption with several layers of rock. The lower part of this ignimbrite is very thick. It contains unique features like the "orbs" mentioned earlier. The upper part of the ignimbrite was erupted in several separate flows.

Scientists believe the main Panizos ignimbrite eruption started steadily from one or more vents. There was a short pause, then the eruption restarted with a lower flow rate. The eruption likely started in the south and moved northward. This huge eruption produced at least 950 cubic kilometers (228 cubic miles) of rock. This is a massive amount of material!

After the main ignimbrite, a flat area of lava flows and a group of lava domes formed. The very last activity was the Cerro La Ramada lava flow, which happened about 6.1 million years ago.

See also

In Spanish: Cerro Panizos para niños

• Aguas Calientes caldera