Mysteries of the Boiling River

Hidden in a remote part of the Amazon rainforest in Peru is a river with water so hot, in some spots it actually boils. In 2019, Rosa Vásquez Espinoza, a biochemist at the University of Michigan who grew up in Peru, found herself standing on the banks of the bubbling waterway. Clouds of steam from the Boiling River rose around her as she inched along a sheer rock wall. She had to be mindful of every step. If she were to fall, the water could scald her to death.

At sea level, water’s boiling point—the temperature at which liquid water turns into a gas—is 100°C (212°F). The Boiling River flows a few hundred meters above sea level. At this higher elevation, water’s boiling point is slightly lower. That means the river starts to boil in spots where the temperature reaches 99°C (210°F).

A river is hidden in a remote part of the Amazon rainforest in Peru. Its water is so hot, it boils in some spots. Rosa Vásquez Espinoza grew up in Peru. Now she’s a biochemist at the University of Michigan. In 2019, she stood on the banks of the bubbling waterway. Clouds of steam from the Boiling River rose around her as she inched along a sheer rock wall. She had to be mindful of every step. If she fell, the water could scald her to death.

Water’s boiling point is the temperature at which liquid water turns into a gas. At sea level, this point is 100°C (212°F). The Boiling River flows a few hundred meters above sea level. At this higher elevation, water’s boiling point is a little lower. When spots in the river reach 99°C (210°F), they start to boil.

Local people have always known of the Boiling River. Some foreigners have even visited it. But scientists have only just recently begun to study it. Vásquez first saw the river in 2017. Two years later, she returned with dozens of other scientists in the largest expedition ever to explore the site.

Vásquez studies microbes called extremophiles, which live in some of the harshest environments on Earth (see Extreme Life). “Microbes are everywhere—in the air, in the water, on our skin, in soil, and on rocks,” says Vásquez. She wants to learn more about the extraordinary microscopic creatures that are able to survive the Boiling River’s high temperatures.

Local people have always known of the Boiling River. Some foreigners have even visited it. But scientists have just begun to study it. Vásquez first saw the river in 2017. Two years later, she returned with dozens of other scientists. It was the largest expedition ever to explore the site. 

Vásquez studies microbes called extremophiles. They live in some of the harshest environments on Earth (see Extreme Life). “Microbes are everywhere—in the air, in the water, on our skin, in soil, and on rocks,” she says. Some are able to survive the Boiling River’s high temperatures. Vásquez wants to learn more about the river’s extraordinary microscopic creatures.

The Boiling River is known to locals as Shanay-Timpishka (shah-NIGH teem-PEESH-kah). The waterway winds for 9 kilometers (6 miles) through the Peruvian Amazon (see Hot Spot). At its start, the river’s waters are actually a comfortable 21°C (70°F), or aboutroom temperature, says Andrés Ruzo. He’s a Peruvian geologist and founder of the Boiling River Project, an organization devoted to understanding and protecting the river. Ruzo traveled to the river in 2011, after hearing tales about it from his grandfather. Since then, he has been studying it in collaboration with local community members.

Locals call the Boiling River Shanay-Timpishka (shah-NIGH teem-PEESH-kah). The waterway winds for 9 kilometers (6 miles) through the Peruvian Amazon (see Hot Spot). At its start, the river’s waters are about room temperature. They’re a comfortable 21°C (70°F), says Andrés Ruzo. He’s a Peruvian geologist and founder of the Boiling River Project. This organization works to understand and protect the river. Ruzo traveled to the river in 2011, after he heard stories about it from his grandfather. Since then, he has been studying it with help from local community members.

Downstream, the river begins to flow over cracks that spew hot water. Ruzo says the hot water may start as rain or melted snow and ice that seeps underground, where it’s heated deep within Earth. Pressure could force the water back toward the surface as thermal jets that warm the river. The water gradually cools as it flows into the neighboring Pachitea River.

The jungle around the Boiling River teems with life. Giant trees and thick vines provide shelter for monkeys, pig-like peccaries, macaws, and other rainforest animals. And even though the river appears inhospitable to plant and animal life in its hottest parts, Vásquez’s team found that it is home to a treasure trove of unique microscopic creatures.

Downstream, the river begins to flow over cracks in the ground. Hot water shoots from these openings. Ruzo says the hot water may start as rain or melted snow and ice. It seeps underground, where it’s heated deep within Earth. Pressure could force the water back toward the surface as thermal jets. The water warms the river. Then it slowly cools as it flows into the neighboring Pachitea River.

The jungle around the Boiling River is full of life. Giant trees and thick vines grow there. They provide shelter for monkeys, pig-like peccaries, macaws, and other rainforest animals. The river’s hottest parts appear too harsh for plant and animal life. But Vásquez’s team found a rich collection of unique microscopic creatures living there.

During the recent expedition, Vásquez took samples from different spots in and along the river. To avoid getting scalded, she used a ladle to scoop up water and sediment. And she gathered soil and scraped clumps of microbes off rocks.

Vásquez collected lichens, which are organisms made up of fungi and plant-like algae living together. She also found blue-green cyanobacteria. These microbes use photosynthesis, the same process used by plants to harness energy from the sun to produce food.

Vásquez took samples during the recent expedition. She collected them from different spots in and along the river. She scooped up water and sediment with a ladle. That way, she didn’t get scalded. And she gathered soil and scraped clumps of microbes off rocks.

Vásquez collected organisms called lichens. They’re made up of fungi and plant-like algae living together. She also found blue-green cyanobacteria. These microbes use photosynthesis to harness energy from the sun to produce food. Plants use the same process.

Vásquez noted the location and conditions—like water temperature, nearby plants, types of rocks, and shade or sun—where each sample was gathered. Those details might help her understand why different microbes live in various parts of the river. She will also try to determine how the microbes relate to the rest of the ecosystem, the community of organisms interacting with their physical environment.

There’s something else Vásquez hopes her studies will reveal: interesting compounds produced by the river’s microbes. Some of these substances might be beneficial to people and the planet.

Vásquez noted the location of each sample she gathered. She also recorded conditions like water temperature, nearby plants, types of rocks, and shade or sun. Those details might help answer the question: Why do different microbes live in different parts of the river? She will also try to determine how the microbes relate to the rest of the ecosystem. That’s the community of organisms within their physical environment.

Vásquez hopes to find something else. Her studies may reveal interesting compounds produced by the river’s microbes. Some of these substances might be helpful to people and the planet. 

As a child in Peru, Vásquez learned about medicinal plants from her grandmother. Her grandmother’s passion for plants rubbed off on Vásquez, who began exploring Peru’s Amazon rainforest as a teenager, on trips with her mother. “Nobody in my family is a scientist, but I have always been curious about how things work,” she says. That led her to wonder about medicines derived from plants and other sources found in the Amazon. “I started to learn about the processes through which nature creates new molecules and realized a lot of them come from microbes,” says Vásquez.

Microbes work like tiny chemists says Vásquez. Some of the compounds they create might help make or inspire new medicines like cancer treatments or infection-fighting antibiotics. Other microbe-made molecules could help clean up oil spills or absorb toxic waste from mines. Certain chemicals might help enrich soil. Such compounds could allow trees to grow again in areas of the Amazon cleared for logging, farming, oil extraction, and mining—common causes of deforestation.

As a child in Peru, Vásquez learned about medicinal plants from her grandmother. She picked up her grandmother’s love of plants. As a teenager, Vásquez began exploring Peru’s Amazon rainforest. She made trips there with her mother. “Nobody in my family is a scientist, but I have always been curious about how things work,” she says. She started to wonder about medicines made from plants and other sources in the Amazon. “I started to learn about the processes through which nature creates new molecules and realized a lot of them come from microbes,” says Vásquez.

Microbes work like tiny chemists, says Vásquez. They create compounds that might help make or inspire new medicines. Some examples are cancer treatments or infection-fighting antibiotics. Other compounds from microbes could help clean up oil spills or absorb toxic waste from mines. Areas of the Amazon have been cleared for logging, farming, oil extraction, and mining. These are common causes of deforestation. Certain microbe-made chemicals might help enrich soil. That could allow trees to grow in these areas again.

Back in the laboratory at the University of Michigan, Vásquez is now examining about 400 samples she and her colleagues collected with permission from the Peruvian government and the local community. A teaspoon of Amazonian soil can contain more than 1,000 different microbes. So Vásquez has a big job ahead of her. The samples likely include many microorganisms that have never been described before. She’ll compare her findings with known microbes to see whether she has discovered something new. She’ll also identify chemical compounds created by the microbes that might be useful.

Vásquez, Ruzo, and their colleagues hope their scientific work will help people understand why it’s important to protect the rainforest from destruction and conserve the huge variety of life found there, including microbes. These organisms could hold the key to curing diseases or improving our lives in other ways in the future.

Vásquez and her team collected their samples with permission from the Peruvian government and the local community. Now she’s back in the laboratory at the University of Michigan. She’s examining about 400 samples. A teaspoon of Amazonian soil can contain more than 1,000 different microbes. So Vásquez has a big job ahead of her. The samples likely include many microorganisms that no one has described before. She’ll compare her findings with known microbes. That will tell her whether she has discovered something new. She’ll also look for chemical compounds from the microbes that might be useful. 

It’s important to protect the rainforest and conserve the huge variety of life found there, including microbes. Vásquez, Ruzo, and the other researchers hope their scientific work will help people understand why. These organisms could hold the key to curing diseases or improving our lives in other ways in the future.