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What’s at the Bottom of Crater Lake?

Crater Lake is one of the country’s most beloved and mysterious national landmarks. With its crystal clear water and stunning views, this destination hides many surprises. Its volcanic history is more unusual than any other lake in America, and its lack of an inlet or outlet keeps its waters clean and adds to the lake’s mystique. What other secrets lie at the bottom of Crater Lake? Let’s find out!

Where Is Crater Lake?

Sitting in south-central Oregon, Crater Lake is 60 miles north of the small town of Klamath Falls. When water collected in the caldera of the collapsed volcano Mount Mazama, it formed the lake. The caldera’s rim ranges from 7,000 to 8,000 feet above sea level.

The Klamath tribe of Native Americans have inhabited the area for centuries, and archaeological digs uncovered sandals that people in early tribes wore. Mazama’s eruption covered the sandals in ash. The lake is a crucial component of their spiritual faith. 

Volcanic Legacy Scenic Byway Overview - Lassen Volcanic, Lava Beds and Crater Lake National Parks

How Deep Is Crater Lake?

Crater Lake is the deepest lake in the United States at 1,949 feet in depth. This also makes it the ninth deepest lake in the world. The water is from rain and snow that filled a basin in the caldera of the Mount Mazama volcano. The caldera is 2,148 feet deep, so the lake is not full. 

Because there are no rivers or streams that flow into or out of the lake, the water comes only from moisture that falls into the basin. Evaporation is the only way the water level goes down. At current climate conditions, the new moisture won’t replace the water in Crater Lake for more than 250 years.

Pro Tip: Don’t rush through this beautiful area! This is How to Plan Your Camping Trip to Crater Lake National Park.

How Did Crater Lake Form?

The lake dates shortly after the Mount Mazama volcano erupted between 6,000 and 8,000 years ago. The volcano collapsed soon after the eruption, leaving a caldera. Eventually, Wizard Island appeared, growing out of the middle of the caldera due to later small eruptions.

Once the surrounding rim of this chasm cooled, rainwater and snowmelt filled the caldera. Because the water comes from no other outside sources, it is some of the cleanest, most pristine water on the planet.

Woman looking out at the view of Crater Lake
Crater Lake is considered the deepest lake in the US.

Can You Swim in Crater Lake?

Yes, you can swim in Crater Lake, but only in designated areas. Be prepared, however, because the water is cold! The average temperature of the water in summer is 57 degrees. Visitors can swim in two places: within 100 feet of Cleetwood Cove, providing you stay 50 feet away from boats, docks, and buoys, and within 100 feet of Wizard Island.

You cannot use any personal watercraft, including inflatable boats or mattresses, paddleboards, kayaks, or canoes in Crater Lake. You can’t use wetsuits, goggles, diving, or scuba gear either. The swimming area is at the bottom of the trail from the rim, which is a climb comparable to 65 flights of stairs when you go back up. Be ready for the entire experience!

Pro Tip: Nearby Klamath Falls has awesome RV parks to stay at when visiting Crater Lake.

What’s At the Bottom of Crater Lake?

What could be lurking at the bottom of a 2,000-foot-deep lake? Hopefully, we won’t find Nessie, but you might be surprised at what lies beneath the lake’s cold, clear waters.

View of Crater Lake at winter time.
Crater Lake is a result of an eruption from the Mount Mazama volcano.

Hydrothermal Vents

In 1987, scientists studied the bottom of Crater Lake with a deep sea rover vehicle. They found hydrothermal vents emitting fluids from within the earth’s crust, helping to balance the pH levels of the water in the lake. Steaming fumaroles, volcanic tubes, and pits exist along the lake bottom. They are all signs of the dormant volcano’s existence.


Moss dating hundreds of years grows at depths between 75 to 420 feet around Wizard Island and most of the crater’s shoreline. Dead moss lies under the living and dates thousands of years. This moss is unique and stunning! 


The dead moss can sometimes be up to 40 yards thick. Eventually, pits and holes appear through the moss, creating tunnels. Some of these holes can be up to 15 feet deep into the moss, but scientists still have no idea how they form.

→ These 7 Awesome Impact Craters That You Can Visit in North America will leave you speechless!

View from underwater looking up at the sun
Various bacteria colonies, moss, fumaroles, and hydrothermal vents can be found on the bottom of Crater Lake.

Pro Tip: After exploring Crater Lake, head to the Oregon coast and stay at one of these 9 Best Oregon Coast RV Parks and Campgrounds.

What Lives At the Bottom of Crater Lake?

Along with moss, fumaroles, and hydrothermal vents, scientists found blue pools and bacteria colonies. Surprisingly, the warmest water in Crater Lake lies at the bottom. It’s 66 degrees there!

This warm water comes from bacterial colonies that have formed mats measuring up to 60 feet across. The only thing scientists haven’t discovered at the bottom of the lake is a monster like the one that may mysteriously reside in Loch Ness.

Crater Lake Is Full of Mysteries

As a famous national park, Crater Lake does not disappoint. Visitors realize almost immediately when gazing across its expanse what a special place this lake is, and they rightly surmise that it is hiding tantalizing secrets beneath the surface. Be sure to venture to southern Oregon to discover what else might lie on the bottom of Crater Lake. 

Tom and Cait at Crater Lake

Lake Superior is another famous body of water with mysterious depths. Find out What’s at the Bottom of Lake Superior?

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Co-Founder, Logistics Queen, Business & Content Manager, and Animal Lover

An Upper Peninsula of Michigan native (aka a Yooper), Caitlin is the organization, big-picture, and content strategy queen of our operation. She keeps everything orderly and on track.

With a background in Business Management, she supports and helps channel Tom’s technical prowess into the helpful content our readers and viewers expect. That’s not to say you won’t find her turning wrenches and talking shop – RV life is a team effort. She keeps the business and the blog moving forward with a variety of topics and resources for our audience.

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She also loves the RV life due to the fact that you can bring your pets along. Sharing information about safely recreating outdoors with your whole family – pets included! – is very important to her. Because of this, Caitlin spearheaded the launch of HypePets in 2023.

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