The Three Sisters Mountains are a trio of volcanic peaks located in the central Oregon Cascades Range. They are named North, Middle and South Sister, the latest being the tallest at 10,358 feet (3,157 meters). Other peaks around are the Broken Top and the Mount Bachelor. The area is known for its volcanic activity, as it is located in the eastern part of the Cascade Volcanic Arc.
This arc extends from northern California to southern British Columbia and is a result of the subduction of the Juan de Fuca tectonic plate beneath the North American plate. This subduction has caused magma to rise to the surface and form a chain of volcanoes that includes famous peaks such as Mount St. Helens and Mount Rainier. Eventually having volcanic eruptions.
The last recorded eruption in the Three Sisters area occurred in South Sister about 2,000 years ago. It produced pyroclastic flows, lahars, and ashfall. Pyroclastic flows are a mixture of hot gas, ash, and rock that move down the slopes of a volcano at high speeds, while lahars are mudflows that can be triggered by heavy rainfall or melting snow on a volcano’s slopes. Ashfall can travel hundreds of miles from a volcanic eruption and can affect air travel, agriculture, and human health.
Since that last event, the area has been relatively quiet, with no major eruptions occurring. However, there have been some signs of renewed activity in recent years. In 2001, a swarm of earthquakes occurred beneath South Sister, indicating that magma was moving beneath the volcano. This activity continued for several years and caused the ground to uplift by several inches. Thankfully, no eruption occurred, and the activity eventually subsided.
Scientists continue to monitor the Three Sisters area for signs of renewed volcanic activity. Nowadays, they use various tools, such as seismometers, GPS, and gas monitoring, to detect changes in the area. Seismometers record earthquakes that can indicate magma movement beneath the surface, while GPS can measure ground deformation caused by magma intrusion. Gas monitoring can detect changes in the composition and amount of gas emitted from a volcano, which can provide clues about the state of the magma chamber.
Despite the lack of recent eruptions, the Three Sisters Mountains remain a potentially active volcanic area. Volcanic hazards such as lahars, ashfall, and pyroclastic flows can pose a significant risk to human life. In addition, volcanic activity can affect air quality, agriculture, and infrastructure.
As the Three Sisters Wilderness Area, is a popular destination for hiking and outdoor recreation. Visitors to the area are encouraged to be aware of the potential hazards of volcanic activity and to stay informed of any changes in the area. The U.S. Geological Survey and the Pacific Northwest Seismic Network provide up-to-date information on volcanic activity in the region.
Besides the potential hazards, the volcanic activity in the Three Sisters also provides opportunities for scientific research. Scientists study the area to better understand the processes that drive volcanic eruptions and to develop methods for predicting and mitigating volcanic hazards. The Three Sisters Mountains are also home to unique ecosystems that have adapted to the volcanic landscape, allowing more ecological research.
However this, don’t let it discourage you from visiting the area. With the help of modern day technology and following the guidelines of tour guides or park rangers, you have all the tools in hand to make this a one of a kind experience. Explore the region while learning about it.