Cascade Volcanoes

The Cascade Volcanoes (also known as the Cascade Volcanic Arc or the Cascade Arc) are a number of volcanoes in western North America. They stretch from British Columbia through Washington and Oregon to Northern California. These volcanoes formed because of the movement of Earth's plates.

Important cities such as Portland, Seattle, and Vancouver lie near these volcanoes. The area is home to many people, and these volcanoes can be dangerous. They have erupted many times before and could erupt again. This is why Mount Rainier is one of the Decade Volcanoes chosen for special study by scientists.

The Cascade Volcanoes are part of the Pacific Ring of Fire, a circle of volcanoes around the Pacific Ocean. They have erupted several times in history. The two most recent big eruptions were at Lassen Peak from 1914 to 1921 and a major eruption of Mount St. Helens in 1980. The Cascade Volcanoes were also the site of Canada's most recent major eruption, which happened around 410 BCE at the Mount Meager massif.

Geology

The Cascade Arc has many volcanoes, with over 4,000 places where lava came out. These volcanoes include different types such as big cone-shaped ones, shield-shaped ones, lava bumps, and small cone-shaped ones. Volcanism here started about 37 million years ago, but most Cascade Volcanoes are younger than 2 million years. The two tallest volcanoes, Mount Rainier and Mount Shasta, both rise very high.

The history of these volcanoes can be split into three main parts. The West Cascades period lasted from 37 to 17 million years ago when volcanoes were very active. The Widespread dormancy period from 17 to 9 million years ago saw less activity and erosion. The High Cascades period began 9 million years ago when volcanoes became active again and continue today.

The volcanoes in the Cascade Arc each have their own special features. Lassen Peak in California last erupted in 1917, and the Mount Meager massif in British Columbia erupted about 2,350 years ago. The Garibaldi Volcanic Belt is the northern part of the Cascade Arc and includes various types of volcanoes.

Largest eruptions

The table below lists some of the biggest eruptions that have happened in the Cascade chain.

Human history

Native Americans have lived near the Cascade volcanoes for thousands of years. They made stories and legends about these mountains. Some stories say mountains like Baker, Jefferson, Shasta, and Garibaldi were safe places during a big flood. Other stories tell of powerful chiefs, with mountains like Hood and Adams throwing fire at each other. Mount St. Helens was often called a beautiful maiden. Many Native American tribes have different names for these mountains.

Hot springs on the Canadian side of the volcanoes were important to the First Nations people. They used these springs for special purposes and thought they were powerful places. In 1792, British explorer George Vancouver began naming the mountains. He named Mount Baker, Mount St. Helens, Mount Hood, and Mount Rainier after people he knew. The quiet time of the volcanoes ended in 1980 when Mount St. Helens erupted. Since then, scientists watch the volcanoes to keep people safe.

Cascadia subduction zone

Main article: Cascadia subduction zone

The Cascade Volcanoes formed because the Juan de Fuca, Explorer, and Gorda Plate move under the North American Plate along the Cascadia subduction zone. This is a long fault far off the coast of the Pacific Northwest, from northern California up to Vancouver Island, British Columbia.

Because this fault is so large, it can create very powerful earthquakes. Energy builds up over time and is released in big earthquakes. Even though there isn’t a deep ocean trench here, the land is slowly pushed together. When the fault moves, it can cause huge earthquakes, like the one in the year 1700.

Famous eruptions

1980 eruption of Mount St. Helens

Main article: 1980 eruption of Mount St. Helens

The 1980 eruption of Mount St. Helens was a powerful event studied by scientists. It happened in the western United States. An earthquake made part of the mountain fall down, and a big cloud of ash rose high into the sky. The eruption changed the land around it.

1914–1917 eruptions of Lassen Peak

Main article: Lassen Peak

In 1915, Lassen Peak erupted and made a tall column of ash and gas. The eruption caused damage nearby and was part of many eruptions from 1914 to 1917. The ash could be seen from far away.

2350 BP (400 BC) eruption of the Mount Meager massif

Main article: Mount Meager massif

The Mount Meager massif erupted in Canada, sending ash far away. This eruption made many types of volcanic rocks and deposits that scientists can still see today.

7700 BP (5783 BC) eruption of Mount Mazama

Main article: Mount Mazama

A very big eruption about 7,700 years ago at Mount Mazama in Oregon caused the mountain to collapse. This made a large crater called a caldera. It also created Crater Lake, and ash from the eruption spread across the Pacific Northwest and into Canada.

13100 BP (11,150 BC) eruptions of Glacier Peak

About 13,000 years ago, Glacier Peak had several very large eruptions. These eruptions sent ash as far away as Wyoming.

Other eruptions

Silverthrone Caldera

Most eruptions of the Silverthrone Caldera happened long ago, with the last one about 1,000 years ago. The volcano’s lava once flowed and was stopped by ice.

Mount Garibaldi

Mount Garibaldi was last active around 10,700 to 9,300 years ago. It made a long flow of thick lava that formed ridges and other features.

Mount Baker

Mount Baker became active again in the mid-1800s after many quiet years. Today, there are signs of heat and gas near its top, but scientists don’t expect an eruption soon.

Glacier Peak

Glacier Peak erupted about 200–300 years ago and has had many eruptions in the past few thousand years.

Mount Rainier

Mount Rainier last erupted in the mid-1800s. It has had many eruptions and mudflows in the past few thousand years.

Mount Adams

Mount Adams was last active around 1,000 years ago. It has had fewer eruptions than other Cascade volcanoes but made several lava flows.

Mount Hood

Mount Hood last erupted about 200 years ago. It made lava flows and a well-known rock formation called Crater Rock.

Newberry Volcano

Newberry Volcano has been very active over time, making many different volcanic features.

Medicine Lake Volcano

Medicine Lake Volcano erupted several times in the past 4,000 years, with the most recent activity about 1,000 years ago.

Mount Shasta

Mount Shasta last erupted around the year 1250 and has been one of California’s most active volcanoes for thousands of years.

Eruptions in the Cascade Range

Eleven of the thirteen volcanoes in the Cascade Range have erupted in the past 4,000 years, with seven doing so in just the last 200 years. These volcanoes have had many powerful eruptions over time. Between eruptions, they can stay quiet for hundreds or even thousands of years.

When these volcanoes erupt, they can send fast-moving flows of hot rock and gas, along with mud and ash, far from the mountain. Ash from eruptions can cause problems for airplanes and affect areas far downwind. The most recent big eruptions were at Lassen Peak from 1914 to 1921, a major eruption of Mount St. Helens in 1980, and a smaller eruption of Mount St. Helens from 2004 to 2008.

List of volcanoes

Main article: List of Cascade volcanoes

Washington has many of the tallest volcanoes. Oregon has many tall peaks, too. Mount Rainier is the highest volcano. Medicine Lake Volcano in California is the biggest. It is followed by Oregon's Newberry Volcano. Here is a list of the tallest Cascade volcanoes. It also includes the tallest in British Columbia (Silverthrone Caldera) and the one that last erupted most recently (Mount St. Helens):