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Hiking the Curiosity Trail - Amazing Geology

Washington is an excellent place to learn about geology and we have selected eight places that are really quite odd.

Washington's trails display some stunning landscapes but some hikes show off especially unique geological oddities such as one-of-a-kind rock formations, land shaped by lava, mysterious mounds and much more. We've compiled some trails across the state that show off these quirky landmarks. 

Washington is an excellent place to learn about geology. Volcanic activity, advancing and retreating glaciers and colliding plate tectonics have all left indelible fingerprints on the landscape. 

These places will set your imagination alight as you dream about a time when tropical forests flourished, volcanoes erupted and massive floods transformed the earth.


Central Washington

Ginkgo petrified Forest Interpretive Trail 

Location: East of Ellensburg
Mileage: 3.0 miles, roundtrip
Elevation Gain: 200 feet

Ginkgo Petrified Forest by Bob and Barb.jpeg
The aptly named Ginkgo Petrified Forest Interpretive Trail is covered in petrified wood. Polished examples are located at the visitor center two miles away. Photo by Bob and Barb.

The Vantage Forest lushly covered this arid sagebrush country west of the Columbia River more than 15 million years ago. Redwoods, walnuts, spruces, and – yes – ginkgo trees flourished. Life was good in the forest until a river of molten lava and ash from a volcanic event in southeast Washington buried the jungle under a flood of molten lava. What happened next was unique: a chemical process called petrification preserved the trees within the new basalt landscape. Flash-forward to the 1930s, when the petrified forest was discovered, specimens excavated and a state park established.

Today, visitors can walk an interpretive trail two miles from the visitor center. Twenty-two partially excavated petrified trees can be viewed along the way. Don't get too excited, however. Because of vandalism, the trees are in holes and behind bars. Still, it's enough to help visualize this shrub-steppe in a whole new way. Head to the visitor center to view polished examples that you can actually touch and to enjoy the sweeping views of the Columbia River and beyond.

> Plan your trip using WTA's Hiking Guide


Umatilla Rock 

Location: Grand Coulee 
Mileage: 5.0 miles, roundtrip
Elevation Gain: 100 feet

Umatilla Rock.jpegUmatilla Rock in Dry Falls State Park. Dry Falls was once the largest waterfall the world has ever seen. Photo by caitoh234.

The Eastern Washington landscape has been transformed by many fascinating geologic forces. The most visible today were repeated cataclysmic Ice Age floods that raged from Montana and sculpted the distinctive coulees of Eastern Washington, as well as the Columbia River Gorge. Imagine a massive wall of water racing at up to 65 miles per hour, carving through the basalt like butter and stripping away everything in its path.

Check out the effects of these floods first hand at Sun Lakes State Park, home to Dry Falls. This was once the largest waterfall the world has ever seen. What's left today is an escarpment 3.5 miles wide and 400 feet high. Sun Lakes is a great place to explore. View it from the visitor center along the highway, or better yet, hike around the prow-like mass of Umatilla Rock and see it rising up from the banks of Dry Falls Lake.

> Plan your trip using WTA's Hiking Guide 


Olympic Peninsula 

Dungeness Spit 

Location: Northern Coast 
Mileage: 11.0 miles, roundtrip
Elevation Gain: 130 feet

Dungeness Spit by jhoppe20.jpegThe Dungeness Spit juts 5 miles out into the middle of the Strait of Juan de Fuca and is thought to be the largest natural sand spit in the world. Photo by jhoppe20.

Imagine the geologic forces that were in play to create the Dungeness Spit, thought to be the world's largest natural sand spit. The jetty curves out into the Strait of Juan de Fuca like a long, slender finger. Originally formed as the glaciers retreated and constantly sculpted by wind, waves, tides and the erosion of nearby bluffs, the spit is still growing and changing each year. A 150-year old lighthouse sits at its end, an important reminder to passing ships that there is a large obstacle in what would appear the be the middle of the channel. The leeward side of the Dungeness Spit is a wonderfully rich tidal habitat full of shorebirds, waterfowl and shellfish, some of which is protected seasonally or year-round with public closures.

Hikers can make the 11 mile round-trip trek to the lighthouse year-round, though they should be aware that the spit can be breached during storms. Bring binoculars, a tide chart and sunscreen; there is no shelter along this hike.

> Plan your trip using WTA's Hiking Guide


Mima Mounds 

Location: South of Olympia
Mileage: 2.75 miles, roundtrip
Elevation Gain: 10 feet

Mima Mounds by Urmi.jpeg
Climb the platform - or better yet, get in an airplane - to grab the best view of the Mima Mounds. Photo by Urmi.

Thousands of unexplained rounded mounds dot the prairie at this National Natural Landmark near our state's capitol. The mounds once stretched for more than 20 miles - bumps (or "pimpled plains") six feet tall and 30 feet wide that from above look positively lunar. Scientists have many theories for why they exist - glaciation, freeze-thaws, earthquakes, gophers - but no one really knows for sure.

Today, Washington's Mima Mounds are important not just because they are the best examples of this unusual geologic feature in the country, but also because the area supports one of the last stands of native prairie in the state. Visitors can walk a short, paved interpretive trail that includes a raised viewing platform, then take to a 2-mile trail that allows hikers to walk amongst the prairie plants and the hummocks whose mystery is still waiting to be solved.

> Plan your trip using WTA's Hiking Guide 


South Cascades 

Ape Caves 

Location: South of Mount St. Helens
Mileage: 2.8 miles, roundtrip
Elevation Gain: 350 feet

Ape Caves by melissapnwa.jpeg
Be sure to bring warm, water-proof clothing, sturdy footwear and at least two headlamps with extra batteries for your exploration of the Ape Caves. Photo by melissapnwa.

Let's get one thing clear straight-away: there have never been any apes in the Ape Caves. Sorry. The name comes from the first of Mount St. Helens' four major eruptive stages and was bestowed upon the caves by an outdoor group called the Mount St. Helens Apes.

Lava from eruptions during the Ape Canyon Stage more than 35,000 years ago created an underground lava tube more than two miles long - the longest continuous lava tube in the United States. Hikers can explore this tube through two major entrances to the Ape Caves. Both require preparation and care as the temperature is a constant 42 degrees, it is completely dark and there are numerous obstacles to contend with. The lower cave is the easier of the two and is appropriate for most equipped hikers. The upper cave is very difficult to navigate and is not for the faint-of-heart nor the unfit or unprepared. We encourage anyone wishing to explore the upper cave to read not only the Hiking Guide entry before going, but also WTA's related Trip Reports, several which are excellent.

> Plan your trip using WTA's Hiking Guide 


Hummocks Trail 

Location: Mount St. Helens National Monument
Mileage: 2.4 miles, roundtrip
Elevation Gain: 100 feet

Hummocks Trail by willtravel4beer.jpegWonder where the side of Mount St. Helens ended up after it blew? This big hill (or hummock) landed right here on May 18, 1980. Photo by willtravel4beer.

The most recent example of geology gone wild is, of course, Mount St. Helens. The eruption of May 18, 1980 forever changed this landscape. One-third of the mountain exploded, flattening everything in its path and raining ash across several states. The explosion triggered lahars and massive debris avalanches that flooded nearby rivers, creating enormous damage to persons and property.

From an ascent of the crater rim to view the expanding lava dome to a walk in the pumice plain where plants are again taking hold more than 30 years later, the Mount St. Helens area is a geologic show-stopper. The Hummocks Trail, in particular, gives hikers a front-row seat to the effects of the lahar. The huge, colorful mounds (up to 500 feet high) are the crushed remains of the original cone that landed here as the debris avalanche narrowed to enter the Toutle River Valley - a melange of Mount St. Helens rearranged in a new hill. Life has come back in full force to this area too: grasses, bushes, willows and flowers are all taking hold. Ponds that dot the area are host to all sorts of wildlife and are themselves an intriguing geologic oddity, as this landscape is so new that a drainage system has yet to become established. If you go, this is a loop trail that is best done in a clock-wise manner.

> Plan your trip using WTA's Hiking Guide 


Puget Sound and Islands 

Flaming Geyser State Park

Location: Near Enumclaw
Mileage: 4.0 miles, roundtrip
Elevation Gain: 450 feet

Flaming Geyser State Park by little burro.jpegWhoa! Is that all there is? Before it was capped, the flame continuously shot 8 feet in the air. Photo by littleburro.

It doesn't look like much today: a candle - or more derisively, a Bic lighter - burning in the middle of a ring of stone. But this "flaming geyser" was once mightily impressive, enough to get it featured in Ripley's Believe It or Not. The geyser is actually a methane seep, discovered by miners exploring for coal in 1911. When initially lit, the blaze shot 25 feet in the air and could sustain an eight foot flame.

It was capped many years ago (hmmm...we wonder why?), and today it displays its rather meager flicker to those who follow the short nature trail to view it. But don't stop there. Flaming Geyser State Park has many miles of trails to explore, plus a model airplane field and nearby rafting and tubing on the Green River. The area is well worth a visit.

> Plan your trip using WTA's Hiking Guide 


Southwest Washington

Beacon Rock State Park 

Location: Columbia River Gorge
Mileage: 7.5 miles, roundtrip
Elevation Gain: 2000 feet

Beacon Rock State Park by explorepnw.jpegAmazing geology! Beacon Rock is the one of the largest free-standing monoliths in the world. Photo by explorepnw.

As the Columbia River flows through the Columbia River Gorge, a 848-foot high thumb is perched on the edge of the water. This is Beacon Rock, the core of a volcano that has otherwise ceased to exist. As one of the largest free-standing monoliths in the world, the pinnacle has seen the passage of time, from the Ice Age floods that carved the Gorge to the arrival of Lewis and Clark in 1805 (who also named it).

That Beacon Rock is still standing today is a testament to Henry J. Biddle, who bought the land and constructed the trail to the top in 1918. Today it is one of the most popular destinations in the Columbia River Gorge. Hikers climb to the top on a series of stairwells and catwalks that are truly something to behold. They don't make them this way any more! From the top, enjoy unimpeded views of the entire Columbia River Gorge.

> Plan your trip using WTA's Hiking Guide