Crater Lake National Park, OR

Updated: Jan 4

No visit would be complete without a visit to the 5th oldest National Park in the US. Crater Lake is the only national park located in Oregon, which is strange considering the incredible nature and beauty that exists in this state. Established in 1902, Crater Lake NP encompasses over 186 square miles. The park is one of the most significant global sites for the study of volcanic geology. It's like an amusement park for anyone with an interest in geology!


Fun Fact #1: Crater Lake National Park (CLNP) is one of the only national parks without a physical street address.


The story of CLNP begins with Mount Mazama. Mount Mazama was a large composite volcano that was built up during the past 400,000 years by hundreds of smaller eruptions of lava flows. Mount Mazama rose to an approximate height of 12,000 feet above sea level. Around 30,000 years ago, these eruptions became larger and increasingly more explosive.


Ultimately, a cataclysmic eruption of Mount Mazama occurred around 7,700 years ago. A single vent on the volcano spewed a towering column of pumice and ash that reached over 30 miles high. A number of additional vents opened around the summit resulting in an even more magma to be released. These lava flows filled valleys around the volcano with over 300 feet of pumice and ashIn a matter of a few days, it had become the largest explosive eruption in the Pacific Northwest in a million years. Having drained a large portion of the magma chamber, the volcano lacked a foundation and began to collapse inward creating a caldera.


Definition: A caldera is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is lost. The ground surface then collapses downward into the emptied or partially emptied magma chamber, leaving a massive depression at the surface. The 'crater' is formed through settling and collapse rather than an explosion or impact.


Over the next 200-300 years, water filled the caldera and the 5 by 6 mile pristine Crater Lake formed.

Fun Fact #2: The lake is 1,943 feet deep at its deepest point, which makes it the deepest lake in the United States; the second deepest in North America; and world wide it ranks ninth for maximum depth.

One thousand foot high vertical cliffs, steep bedrock slopes, and talus piles define the caldera walls. There are almost no 'beach areas'; instead the steep slopes above the surface of the lake continue beneath its waters to great depths. The photo below courtesy of USGS shows details of features beneath the surface of Crater Lake using data from a bathymetry survey. Colors range from orange to blue with increasing water depth.

The rim of the caldera has been steadily eroded by the forces of nature. Melting snows in the summer carry vast amounts of material into the lake. Sliding snow in the winter adds to the erosion. Finally, add the sand blasting winds and destructive force of ice and it's easy to see that nature will ultimately win this battle with the caldera rim.

Fun Facts #3: Crater Lake is isolated from surrounding streams and rivers, thus there is no inlet or outlet to the lake. All of the water in the lake comes from rain and snowmelt. Despite this dependency on weather, the water level has been very stable, varying only 16 feet over the past 100 years.


Fact #3 and #4 are closely related.


Fun Fact #4: Crater Lake National Park is one of the snowiest places in the US. Seventy percent of the CLNP annual precipitation occurs as snow from November through March. Average snowfall is 575 inches (48 feet), and snow depths of 100 to 200 inches (8 to 16 feet) are received each winter and are long lasting throughout much of the park. The greatest seasonal snow accumulation occurred in 1932-1933 when 834 inches (69.5 feet) was recorded. Even during our visit in late July snow was still visible along underexposed hillsides.

So how does the lake level remain stable with such high snowfall totals and no known outlet? Where does all the water go if the lake doesn't rise? Precipitation rates are more than twice the evaporation rates, so there is a lot of water that seemingly goes unaccounted for. Scientists have discovered that steady seepage is what maintains the water balance. Water seeps out of the porous caldera’s walls at a rate of about 2 million gallons of water an hour. Where that water goes is still a mystery!


With water seeping out at approximately 2 million gallons/hour, you would think water doesn't remain in the lake very long. Wrong! Hydrology studies indicate lake water retention time (the amount of time water spends in Crater Lake) is approximately 157 years. Obviously many unanswered questions remain.


Fun Fact #5: Staying on the topic of water, the blog photos of the 'blue' water have not been enhanced by software. Crater Lake's water is so blue because there is hardly anything else in it – just water. It’s not pure water, but it’s close. Water molecules with no sediments, algae, pesticides or pollution, absorb red, orange, yellow and green wavelengths of light but scatter blue ones. In deep water those blue wavelengths are often redirected up to the surface, where they are visible and contribute to the lake's intense color. The key is to have relatively pure water and lots of it to absorb all the other colors. Luckily Crater Lake has about 4.6 billion gallons of water to work with.

Along the shoreline the water takes on a prismatic appearance. Light penetrates to depths in excess of 100 feet compared to 65-80 feet in most other alpine lakes.

Fun Fact #6: You can swim in Crater Lake. Although the lake is surrounded by 1,000 foot high cliffs, there is one legal/authorized trail that leads to the shore – Cleetwood Cove Trail. The trail is steep and strenuous hike with a 700 feet elevation drop over 1.1 miles through a series of long switchbacks.

The trail is usually open from mid-June to late October.

After spending so much of the day driving around the rim road, it felt odd to be so close to the water's edge.

The rocky shoreline provided plenty of areas for people to swim without being on top of each other. Actually the National Park Service estimates that only 10% of Park visitors dip their toes into the water and ...

... you just knew that we were going to be part of that 10% even though the average surface temperature of the lake in the summer is just 57°F /14°C.

To protect the clarity of the lake and decrease the possibility of introducing invasive species only bathing suits and basic clothing may be worn. No inner tubes, snorkel equipment, kayaks, etc. Park Service staff are available at the trailhead to answer any questions about restrictions.

Fun Fact #7: The two islands rise above the surface of Crater Lake are remnants of ancient volcanic activity.

  1. Wizard Island

  2. Phantom Ship

Rising 700 feet above the water on the west side of Crater Lake is Wizard Island. This perfectly preserved cinder cone volcano is thought to have erupted within a few hundred years of the climactic eruption of Mount Mazama. Andesite lava spewed from a single vent on the lake's floor. The lava which flowed at temperatures exceeding 2000°F had the viscosity of smooth peanut butter. Moving slowly, it accumulated over time until the cinder cone pierced the water and 'island building' began.

The steep sided cinder cone is capped on the summit by a crater about 250 feet in diameter and 80 feet deep. Most summers, NPS offers boat rides out to the island but due to COVID concerns the boats were not operating in 2021. I would have loved to hiked on the island and experience standing on the rim of a crater within a crater!

At first glance, Phantom Ship Island situated in the southeast end of the lake resembles a pirate ship with tall masts sailing on the lake. Emerging about 160 feet above the lake’s surface, the island is the remnant of an ancient ridge/dike that transported lava to the surface. The 500 x 200 foot andesite spires are over 400,000 years old, representing some of the oldest rock in the Crater Lake basin. The Sun Notch Viewpoint offers the best view of Phantom Ship Island.

Fun Fact #8: Driving the scenic 33-mile loop that follows the caldera rim can be an all day event. Most guides recommend planning at least 2 hours to complete the drive but with over 30 overlooks, picnic areas, hikes and amazing geologic sites plan on many more hours.

Among the most significant geologic features is Hillman Peak, the brown-colored summit left of center. Hillman is the highest point on the rim at 8,156 feet. It formed as a parasitic volcanic cone when lava began oozing from a vent/crack on the slopes of Mount Mazama. When Mazama collapsed the Hillman cone was cut in half exposing its inner structure. The rocky crags, below and to the right of the peak, are feeder tubes that 70,000 years ago transported lava to the cone.

Other significant sites include Llao Rock, the darker gray rock with the steep face left of center. Llao rises 1,800 feet above the lake and tells a story that covers 170,000 years of geology. I promise this is the only geology lesson in the blog.


Llao Rock was formed during a volcanic eruption that occurred about 100 years before the eruption that destroyed Mount Mazama. The eruption began with an explosion that dug a 500 foot crater into the northwest side of Mount Mazama. The explosion was accompanied by large cloud of ash that rose high above the volcano and was deposited on the slopes of Mount Mazama. The thin trace of ash is labeled (RL-A). The rock layers below the the RL-A deposit are older volcanic rock dating back between 42,000-172,000 years.

After the explosive phase, rhyodacite lava (RL) filled the explosion crater with a dome (1,200 foot thick in the middle and tapering at the ends) that covered over the vent. Llao Rock is the top of this dome. Later during the initial phase of the cataclysmic eruption of Mount Mazama, Llao Rock was covered with a 90 foot thick layer of pumice (CP). Pumice is a fine-grained volcanic rock that is formed when volcanoes erupt explosively.

Pumice Castle, with its orange-brown turrets is one of the most colorful volcanic formations on the east rim of the caldera. It's often missed by visitors and you can see why from this photo. The castle is made of layers of pumice and other rocks that was coughed up by Mt. Mazama; some so hot they welded together. These volcanic deposits were buried and compacted by other lavas, then exposed when Mt. Mazama collapsed. The castle stands 1,300 feet above the lake surface. A foundation of andesite lava has kept Pumice Castle intact, while surrounding pumice deposits have eroded away.

The last geologic feature I'll highlight is the Pinnacle Vents. These towering needle-like formations of rock, called fossil fumaroles, projecting from the Sand Creek Canyon floor, were formed during the cataclysmic eruption of Mount Mazama.

The light colored deposits on the lower canyon wall are mainly rhyodacite pumice from the top layer of the magma chamber. The overlying darker rocks are from the late phase and include andesitic composition from the lower part of the magma chamber.

When these super hot flows came to rest it formed 200-300 foot thick gas-charged deposits. For perhaps years afterward, hot gas moved to the surface and slowly cemented ash and pumice together in channels and escaped through fumaroles. Erosion later removed most of the surrounding loose ash and pumice, leaving tall pinnacles and spires.

Watchman's Peak

Because most of the day was spending driving the Rim Road we didn't have much time to hike but we did squeeze in a short hike 1.7 mile roundtrip to Watchman Lookout Station on top Watchman Peak. If you squint you can see the tower in the photo of Watchman Peak

This photo taken from the edge of the parking lot provides a better view of the Watchman Peak and the dike (D) that cut through older lava flows (OLF) and transported dacite lava to the vent (V) where it erupted just below the Watchman Peak. The lava that spewed from this vent is estimated to be 53,000 years old and happened well before the destruction of Mount Mazama.

At the top we had a great view of Wizard Island and Crater Lake.

From the peak, looking to the east we could see smoke from wild fires that had begun burning a week or so earlier. Little did we know how large the Bootleg Fire would grow over the coming month.

Although it was a quick day, we really enjoyed the Crater Lake National Park experience.

While we were at Crater Lake we stayed in an Airbnb in Chiloquin, OR. Each morning we woke up to a prairie dog show in the backyard. These 6 inch tall clowns chased each other, jumping in and out of the underground tunnels and stopping occasionally to munch on grass.

Driving through the town we could see burn scars from a 2020 wildfire. It's hard to imagine how terrifying it must be to personally experience one of these monster fires. One year after the fire, crews were still removing trees and debris.

As if this region hadn't already suffered enough, on July 7th, Oregon issued the first incident report on the Bootleg fire.

When we left Chiloquin heading for Mount Hood, smoke was visible along several sections on Highway 97.

At one point, over 2,200 personnel were fighting the fire. It was the 3rd largest fire in history Oregon since 1900. At the fire's fastest growth in mid July, it grew at about 1,000 acres per hour and it became the 2nd largest wildfire in the US that year.


Before being fully contained on 15 August 2021, the Bootleg Fire had burned 413,765 acres (1,674 km2; 647 square miles).


For a traveler through the area it was a bit nerve-wracking so I can only imagine the stress it creates for people living in or near the path of these monster wildfires.

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