Three Sisters (Oregon) facts for kids
Quick facts for kids Three Sisters |
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The Three Sisters, looking north
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| Highest point | |
| Elevation |
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| Prominence | 5,588 feet (1,703 m) (South Sister) |
| Listing | US most prominent peaks, 85th (South Sister) |
| Geography | |
 Three Sisters
Location in Oregon
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| Location | Lane and Deschutes counties, Oregon, U.S. |
| Parent range | Cascade Range |
| Topo map | USGS South Sister and North Sister |
| Geology | |
| Age of rock | Quaternary |
| Mountain type | Two stratovolcanoes (South, Middle) and one shield volcano (North) |
| Volcanic arc | Cascade Volcanic Arc |
| Last eruption | 440 CE |
| Climbing | |
| Easiest route | Hiking or scrambling, plus glacier travel on some routes |
The Three Sisters are three tall volcanic mountains in Oregon, a state in the United States. They are part of the Cascade Volcanic Arc, which is a chain of volcanoes in western North America. This chain stretches from British Columbia in Canada, through Washington and Oregon, and into Northern California.
Each of the Three Sisters is over 10,000 feet (3,000 meters) high. They are the third, fourth, and fifth tallest peaks in Oregon. These mountains are located in the Three Sisters Wilderness, near the towns of Sisters. The area around them is home to many different plants and animals. It gets a lot of snow, some rain, and has big temperature changes between summer and winter. Many people enjoy climbing and hiking on these mountains, especially South Sister.
Even though they are called "Three Sisters," each mountain is unique. They have different rock types and eruption histories. North Sister and Middle Sister have not erupted in about 14,000 years. Scientists think they are unlikely to erupt again. South Sister last erupted about 2,000 years ago. It could erupt in the future, which might affect people living nearby. In 2000, satellites saw the ground near South Sister bulging. Because of this, scientists started watching the area more closely.
Contents
Exploring the Three Sisters Area
The Three Sisters mountains are found in Oregon, about 10 miles (16 km) south of the town of Sisters. They sit on the border of Lane and Deschutes counties. These mountains are also within the Willamette National Forest and Deschutes National Forest.
These three peaks are the third, fourth, and fifth highest in Oregon. They are home to 16 named glaciers, which are large bodies of ice. Early settlers named the mountains Faith, Hope, and Charity. Today, they are known as North Sister, Middle Sister, and South Sister.
The Three Sisters Wilderness
The Three Sisters Wilderness is a very large protected area. It covers about 281,190 acres (1,138 km²). This makes it the second-largest wilderness area in Oregon. It was set aside by the United States Congress in 1964.
This wilderness area has about 260 miles (420 km) of trails. You can find many forests, lakes, waterfalls, and streams here. About one-third of the wilderness area is called the Alpine Crest Region. This part includes the Three Sisters and a nearby mountain called Broken Top. It has many glaciers, lakes, and meadows that people love to visit.
Mountain Weather and Glaciers
The weather around the Three Sisters changes a lot. This is because of something called a rain shadow. Air from the Pacific Ocean rises over the western side of the mountains. As it rises, it cools and drops its moisture as rain or snow. This means the western slopes get a lot of precipitation.
Once the air crosses the mountains, it becomes warmer and drier. So, the eastern slopes get less rain and snow. In summer, temperatures can reach 80 to 90°F (27 to 32°C). In winter, they can drop to -20 to -30°F (-29 to -34°C).
The Three Sisters have about 130 snowfields and glaciers. These are found at different heights on the mountains. The Collier Glacier is between North Sister and Middle Sister. Even though it has shrunk a lot, it is still considered one of the largest glaciers here.
When glaciers melted after the Little Ice Age, they left behind spaces that filled with water. This formed lakes held back by natural dams made of rock and dirt, called moraine-dammed lakes. These lakes are common in the Three Sisters Wilderness.
Sometimes, these natural dams can break, causing sudden floods or mudflows. In 1966, a flash flood happened because of an avalanche. Scientists have studied lakes like Carver Lake on South Sister. They found that if Carver Lake's natural dam broke, it could cause a large mudflow. This could be dangerous for visitors and the town of Sisters.
Wildfires and Forests
Before people settled in this area, wildfires often burned through the forests. This was especially true for the ponderosa pine forests on the eastern slopes. For the past 100 years, people have tried to stop these fires. This has caused the forests to become very thick. Now, when fires do start, they can be much larger and more dangerous.
In recent years, wildfires have become more common in the Deschutes National Forest. For example, in 2012, a lightning strike caused a fire that burned a large area. In 2017, officials closed a big part of the wilderness due to 11 lightning-caused fires. Because of these fires, officials are now planning controlled burns. These controlled fires help protect the forests and wildlife.
How the Mountains Formed
The Three Sisters are part of the Cascade Range. This range has many volcanoes that formed over time. Each of the Three Sisters volcanoes formed at different times. They also formed from different types of molten rock, called magma.
Like other Cascade volcanoes, the Three Sisters were fed by magma deep underground. This magma is created when the Juan de Fuca Plate slides under the North American tectonic plate. This process is called subduction.
The mountains were also shaped by past ice ages. During these times, large glaciers moved across the land. These glaciers slowly carved away at the mountains, changing their shape.
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The Three Sisters are unique because they are very close together. Other volcanoes in the Cascades are usually much farther apart. This area is one of the most active volcanic regions in the Cascades. Nearby peaks include Belknap Crater, Mount Washington, and Mount Bachelor.
Most of the volcanoes around the Three Sisters are made of a dark, runny lava called basalt. But South and Middle Sister also have a lot of lighter, thicker rocks like andesite and rhyolite. Thicker magma can cause more explosive eruptions.
North Sister: The Oldest Sister
North Sister, also called "Faith," is the oldest of the three mountains. It is also the most worn down by weather and ice. It is a shield volcano, which means it has gentle slopes like a warrior's shield. Its top is 10,090 feet (3,075 meters) high.
North Sister is mostly made of basaltic andesite, a type of dark volcanic rock. The oldest rocks on North Sister are about 311,000 years old. Scientists believe its last eruption was about 46,000 years ago. Over time, erosion has worn down North Sister a lot. It used to be much taller, over 11,000 feet (3,350 meters) high.
Middle Sister: The Cone-Shaped Sister
Middle Sister, also known as "Hope," is a stratovolcano. This type of volcano has a classic cone shape. It is the smallest and least studied of the three. Middle Sister started erupting about 48,000 years ago. Most of its growth happened between 25,000 and 18,000 years ago.
Middle Sister is 10,052 feet (3,064 meters) high. Its eastern side has been heavily shaped by glaciers. The western side is still mostly in its original shape. Middle Sister has the most ice cover of the Three Sisters. The large Collier Glacier flows down its north side.
South Sister: The Tallest Sister
South Sister, also called "Charity," is the tallest of the three, standing at 10,363 feet (3,159 meters). It is also a stratovolcano. Its current shape is less than 50,000 years old. South Sister last erupted about 2,000 years ago.
Unlike its sisters, South Sister has a crater at its top that has not been worn away by erosion. This crater is about 0.25 miles (0.4 km) wide. Inside the crater is a small lake called Teardrop Pool. This is the highest lake in Oregon.
Even though South Sister is relatively young, most of it has been shaped by glaciers. These glaciers have carved out valleys and left behind piles of rock and dirt.
Recent Activity and Future Dangers
Scientists have studied the Three Sisters area for many years. Early ideas suggested that the mountains were once part of one giant volcano that collapsed. However, later studies showed that each volcano formed separately.
North and Middle Sister are not expected to erupt again. But an eruption from South Sister could be dangerous for people nearby. If it erupted, ash could fall on the city of Bend. Mudflows and fast-moving hot gas and rock could also rush down the mountain. Scientists think the most likely eruption would be ash and slow lava flows.
In 2000, satellites detected that the ground west of South Sister was bulging. This meant that magma was pooling about 4 miles (6 km) underground. Scientists worried that the volcano was waking up. In 2004, there was a series of small earthquakes in the area. By 2007, the bulging had slowed down.
Because of this activity, scientists have increased their monitoring of the Three Sisters. They use GPS to track ground movement and study gases coming from the area. This helps them understand what the volcano is doing and if it might erupt.
Wildlife and Plants
The plants and animals around the Three Sisters depend on where they live on the mountains. On the western slopes, where it rains a lot, you find forests of Douglas fir and Western hemlock. Other trees like mountain hemlock and noble fir also grow here. Smaller plants like vine maple and rhododendron grow under the trees.
Higher up, around 6,500 feet (1,980 meters), the forest starts to open up. This is the subalpine zone. Mountain hemlock trees are common here. Meadows have grasses, dwarf willows, and colorful flowers like lupine and Indian paintbrush.
The very top parts of the mountains, above 7,500 feet (2,286 meters), are the alpine zone. This area has harsh weather with lots of snow and cold temperatures. You'll find patches of whitebark pine trees near the tree line. Most of the area is bare rock.
The lower eastern slopes get less rain. Here, you'll see forests of ponderosa pine. Underneath these trees, plants like greenleaf manzanita and antelope bitterbrush grow.
Many animals live in the Three Sisters area. You might see birds like blue grouse and small mammals like pikas and chipmunks. Larger animals include mule deer, Roosevelt elk, and American black bear. Predators like bobcats, cougars, coyotes, and bald eagles also live here.
Human History and Recreation
The Three Sisters area has been used by people for a very long time. Native American groups like the Northern Paiute and Molala lived here after the last ice age. They gathered berries, made baskets, hunted, and created tools from obsidian.
The first European to see the Three Sisters was explorer Peter Skene Ogden in 1825. Later, in the 1840s, settlers began to approach the mountains. They likely gave the peaks their individual names. Explorers like John C. Frémont used the Three Sisters as a landmark.
In 1862, a route called the Scott Trail was made over Scott Pass. This trail helped connect the Willamette Valley to ranches and gold mines. Later, the McKenzie Pass Road replaced this trail.
In the late 1800s, shepherds brought large herds of sheep to graze in the mountain pastures. By the 1890s, there were too many sheep, and the land was being overgrazed. Sheep grazing was eventually banned in the 1930s and 1940s.
In 1892, President Grover Cleveland created the Cascades Forest Reserve to protect the forests. This reserve later became part of the United States Forest Service. Over time, the area was divided into the Deschutes National Forest and the Willamette National Forest.
Many of the glaciers on the Three Sisters were first described in 1916. The Collier Glacier was studied and photographed for many years. These photos showed how much the glacier had shrunk between 1910 and 1994.
In the 1930s, there was a plan to make the Three Sisters area a National Monument. Instead, it became a "primitive area" in 1937. Later, in 1964, it became part of the National Wilderness Preservation System. This protected the area from development. Over the years, more land was added to the Three Sisters Wilderness.
Climbing the Three Sisters
The Three Sisters are very popular for hiking and mountaineering.
North Sister is the most challenging and dangerous to climb. This is because it has a lot of loose rocks. It is sometimes called the "Beast of the Cascades." The first recorded climb of North Sister was in 1857. Today, the common trail is about 11 miles (18 km) long.
Middle Sister can also be climbed. The round-trip hike is about 16.4 miles (26.4 km) long.
South Sister is the easiest of the three to climb. It has a trail that goes all the way to the top. The main route is about 12.6 miles (20.3 km) round-trip. It is a very popular climb, especially in August and September. Up to 400 people might climb it on a single day!
See also
In Spanish: Three Sisters (Oregón) para niños
