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Geology Rocks Day 4: Beauty and the Beast, On the Trail of The Big One

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Figure 1. Overview of the Day 4 route. Red areas are landslides recently mapped using lidar, a high-accuracy-laser scanning technique.

The layover day ride down Highway 101 to Brookings is one of the most beautiful stretches of coast in the world. You should try to ride at least a part of it. Steep rugged mountains drop into the sea, and clean empty beaches are interspersed with thick forest, sheer cliffs, sea stacks, and arches. For those in need of a rest before the Day 5 climb, a jet-boat ride up the Rogue River, one of the premier fishing and whitewater rivers in the west, is almost as beautiful.

The rocks continue to be a variety of exotic terranes, made largely of mélange, folded and broken sandstone, and serpentine. You will see patches of bright green serpentine just south of Gold Beach after you cross Hunter Creek, just south of Cape Sebastian, and between Myers Creek and Pistol River. In many places you may see large knockers standing out on the open grassy slopes. The highly varied geology of mélange and knockers is largely responsible for the spectacular coastal scenery, as the waves accentuate the chaotic nature of the bedrock to produce a dramatic coastline.

You may have a harder time noticing that the slopes above, and sometimes beneath, the highway are riddled with hundreds of landslides. Using new laser-scanned topographic maps, geologists have identified several thousand ancient landslides lurking along the slopes of the coastal mountains between Gold Beach and Brookings, making this area one of the most landslide-rich in the country.

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Figure 2. The broken rocks of the exotic terranes make for spectacular coastal scenery with many cliffs and offshore rocks and islands. The orange line marks the route.

The force behind this landscape, both the 200 million-year-old mélange and the very recent landslides, is subduction. Subduction happens where an oceanic plate and continental plate collide, and the oceanic plate slides slowly beneath the edge of the continent. The boundary between the plates is a fault zone, typically hundreds of miles long, along which the ocean plate drives beneath the continent in a series of 50-foot jerks, separated by hundreds of years of steady buildup of pressure.

These jerks are called subduction megathrust earthquakes, and are typically magnitude 8 to 9. The magnitude-9 earthquake in Tohoku, Japan in 2011 is the most memorable recent example. During each earthquake, the rocks along the fault get broken and mixed, and over millions of years, after thousands of earthquakes, a thick layer of broken rock forms around the fault. This is how the mélange we see in the hills is formed, and in the case of these exotic terranes, the earthquakes that formed them occurred hundreds of millions of years ago, along a subduction zone that died 150 million years ago.

However, a new subduction zone started up along the Pacific Northwest coast perhaps 50 million years ago. It is still active, and is slowly building up stress today, preparing for the next megathrust earthquake. In between earthquakes, the fault is locked and both plates move together. In fact, an ultra-precise GPS station at Cape Blanco, our Day 3 option destination, is currently moving towards Alberta, Canada at the rate of a little over a half inch a year. At that rate it has moved, along with all of western Oregon and Washington, about 15 feet since the last Cascadia megathrust earthquake in 1700 AD. At the scale of tectonic plates, the crust of the earth is flexible, and it can bend like a bow as shown in Figure 3. As the oceanic plate pushes against the continent along the locked fault, the rocks along the coast not only move steadily to the NE, they also rise as the continent flexes under the strain. When the earthquake finally occurs, the flex relaxes and the whole edge of the continent lurches 15-30 ft back towards the southwest, and the rising areas along the coast subside as the flex relaxes. Fifty miles offshore, the leading edge of the continent rises abruptly, displacing a huge amount of water and producing a bulge on the surface of the ocean. As the bulge of water collapses, it sends out huge tsunami waves, which arrive on the coast in as little as 15 minutes.

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Figure 3. The subduction earthquake cycle. The colliding plates remain locked for centuries, slowly bending as stress builds up. When the earthquake occurs, the bent plate snaps back, and the tip of the overriding plate flips up, making a huge bulge in the ocean surface, which turns into a devastating tsunami.

Computer models of potential future waves have been completed for the entire Oregon coast, and in many parts of coast you are riding today, waves as high as 80 to 100 feet above sea level are possible. The tsunami in Japan in 2011 killed over 16,000 people who were unable to evacuate in time, so it is important to know how to evacuate safely in the unlikely event of a Cascadia tsunami. You can download an app for your phone to show the way to safety or view evacuation maps for Oregon coastal communities here.

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An incredible job of geologic sleuthing has shown that the Cascadia subduction zone has produced 42 megathrust earthquakes in the last 10,000 years, 19 of which were magnitude 9 to 9.2, and another 23 of “only” magnitude 8 to 8.7. The thousands of landslides along the coast are largely the result of this violent history.

In addition to generating a tsunami, the next Cascadia earthquake will cause very strong shaking along the coast for up to five minutes, which in turn will trigger landslides to move on the steep coastal slopes made up of sheared and shattered mélange rock. Geologists expect to see thousands of landslides occur during the next Cascade earthquake, and Highway 101 may be blocked for years.

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Figure 4. Looking east at the coast and ocean floor, you can see where the route lies in relation to the Cascade Subduction Zone. The giant fault slopes back beneath the land, and the red line on the ocean floor marks the point where it reaches the surface of the earth. This red line corresponds to the purple line on the first panel of Figure 2.

The giant fault that produced all of these earthquakes lies just a few miles off the coast along the ride, and because the fault slopes gently to the east underground, it is only 15 miles away from the route, straight down. Don’t worry: The odds of an earthquake occurring on the day you ride the coast are about 1 in 50,000! This Pulitzer-prize-winning article about the impact of the next Cascadia earthquake is worth a read.

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Day 7: Glendale to Myrtle Creek

07_Glendale_to_Tri_City[1] Day7-5 As it should be, the last day of this year’s Week Ride is relatively short and easy. There’s very little elevation gain, and it’s gently descending riding for the last 34 of the day’s 42 miles.

Most of this route is a designated BLM Back Country Byway and Oregon State Tour Route. Active railroad tracks are adjacent to the road. They follow the original Oregon and California Railroad Company grade built in 1869, and many historic railroad structures can still be seen along the route.

Day7-2The route starts by leaving Glendale on a county road for about five miles. That becomes BLM-maintained Cow Creek Road for 30 miles, before bypassing the community of Riddle and crossing over the freeway to arrive back at South Umpqua High School.

There is a very slight hill to climb for a short distance before the road reaches Cow Creek, a tributary of the South Umpqua River. The road then follows Cow Creek through conifer and hardwood forested areas. Beware that poison oak is prevalent along this route. Using only designated rest and water stops along the route will avoid exposure to this obnoxious plant.

Day7-7Panning for gold still occurs in Cow Creek, and a sign 17 miles from Glendale provides information about recreational gold panning. At this Recreational Gold Panning Area, thousands of feet of streambed are open for public gold panning. The remaining streambed is either privately owned or reserved mining claims.

After a rest and a water stop along the route, lunch and a celebration will happen at the finish.

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State Parks Partnership Highlights Oregon’s Most Beautiful Spots

Cape_Blanco_Lighthouse,_Oregon,_USACycle Oregon and Oregon State Parks are a winning team. The state agency partners with Cycle Oregon to allow its locations to be used for rest stops and overnight camps during events, which in turn exposes more people to Oregon’s parks.

“Cycle Oregon has opened up a huge promotional opportunity for us,” says Alex Phillips, a Bicycle Recreation Specialist for Oregon Parks & Recreation Department. “When people come through on their rides, it lets us show our parks to people who might not have otherwise known about them.”

_MG_4437The two organizations have collaborated on exposing people to the beauty of Oregon in another way, too. Cycle Oregon and Oregon State Parks joined forces in 2009 to create the Scenic Bikeways program. Cycle Oregon provided a signature grant of $50,000 to get the program going, and State Parks is responsible for designating and maintaining the routes.

“Cycle Oregon provided the seed to get the Scenic Bikeways program going,” says Phillips. “It wouldn’t have been able to survive without that.”

Smith_Rock_in_the_AfternoonThe Scenic Bikeways program designates cycling routes in various regions of Oregon, creating accessible ways for visitors to see the state’s natural beauty. The Scenic Bikeway program also brings economic development to the designated areas—in 2014, Scenic Bikeways brought $12.4 million into the Oregon economy.

The first official bikeway in Oregon, and in the whole United States, was the Willamette Valley Scenic Bikeway. This 134-mile Bikeway gets ridden over 18,000 times a year, including day and overnight trips.

“The Willamette Valley is Oregon’s most popular Scenic Bikeway,” says Phillips.

5yrPrintandWeb-1040036-587x391Those looking for a quieter experience—and “a great training ride for Cycle Oregon,” according to Phillips—should check out the Blue Mountain Century Scenic Bikeway. This 108-mile route in Eastern Oregon, which is filled with long, rolling hills, only sees about 1,000 riders a year.

Cycle Oregon’s Week Ride this year travels one of the newest bikeways, the Wild Rivers Coast Scenic Bikeway, an out-and-back route that starts and ends in the quaint, eccentric town of Port Orford.

“The Wild River bikeway goes inland along the scenic Elk River, and offers several opportunities for views along the coast,” says Phillips. “Cycle Oregon riders will enjoy incredible views from Cape Blanco State Park—to the lighthouse, and all up and down the coast.”

Learn more about the Scenic Bikeways throughout Oregon.

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Day 6: Indian Mary Park to Glendale

06 Indian Mary to GlendaleDay6-1The Day 6 route follows the Rogue River downstream to the end of the BLM road, 12 miles from start. At that point, the only way to experience the river is by raft, jet boat, or on foot along a hiking trail. The 40-mile Rogue River National Recreation Trail is in the heart of the National Wild and Scenic Rogue River Canyon, and travels downriver from Grave Creek, the location of the first stop of the day. Since you’re not hiking or riding in a boat, the only option is to ride up along Lower Grave Creek to the community of Wolf Creek. Grave Creek is the site of numerous gold mines, as evidenced by claim signs along the road.

Day6-4The climb to Wolf Creek is moderate-to-easy compared with hills ridden the last few days. It ends at the historic Wolf Creek Inn, the oldest continuously operated hotel in the Pacific Northwest (built in 1883). This structure is listed in the National Register of Historic Places, and is a heritage site owned by the Oregon State Parks. The Inn is currently being remodeled and full time innkeepers are needed. Feel free to drop your resume in the mailbox when we pass by.

 

Day6-8After a rest stop on the grounds of the Inn, you’ll ride on Interstate 5 for about two and a half miles. This freeway section includes the biggest climb of the day, on unusually wide shoulders over Stage Pass (1,830’). After a short descent on the freeway shoulder, the route exits onto county roads that travel through Azalea, and then a 15-mile ride to Chief Miwaleta Park, for lunch on the banks of Galesville Reservoir. The dam impounding the reservoir was constructed in 1986 and provides electricity and water for irrigation.

Day6-7The ride from Azalea to lunch is slightly uphill, which results in a descending ride all the way to the finish. For those who want some more miles and additional very gradual climbing, an optional out-and-back loop is available. If you choose to ride the option, you’ll leave lunch and ride 10 miles to a forest service campground. After a stop in the campground, the optional route returns to the lunch site, and then follows the main route back through Azalea to Glendale, for an overnight stay on the grounds of Glendale High School.

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Weekend Ride Brings Families and Friends Together

IMG_6435With great anticipation, friends and families arrived Friday night at Oregon State University (OSU), where the staff welcomed everyone with open arms to kick off this year’s Weekend Ride through the Willamette Valley. That night, riders gathered in large groups over good food and beer, and music and entertainment, as they rekindled friendships and began new ones.

The first day of riding on Saturday was particularly well received, with short, medium, and long route options to choose from. From OSU, riders went west toward the Coast Range. The short and medium routes took Cycle Oregon Weekend (37 of 148)mostly flat, quiet roads through agricultural and forested Cycle Oregon Weekend (59 of 148)areas, as they cruised past small towns. The long route went farther toward the coast and included some short climbs and long descents as it followed a ribbon-smooth single-lane road along the south fork of the Alsea River. The Alsea summit was a popular place for riders to catch their breath and snap some pictures before the final stretch back to OSU.

At night the university was filled with friends, family, and laughter as folks played Frisbee, cheered on the kid’s bike parade, listened to music, and celebrated the day’s adventure.

On Sunday morning, riders huddled, sipping coffee while waiting for rainy weather to clear. Once they eventually set off, everyone enjoyed a flat cruise through the countryside. All routes included portions of the Willamette Valley Scenic Bikeway. Those who chose the long route Cycle Oregon Weekend (94 of 148)went through forests and past historic buildings while reaching the day’s only climb. Lunch was in the picturesque town of Brownsville, followed by a stop at Thompson’s Mill before finishing the ride at OSU to a mass of cheering spectators.

Although temperatures were far from sweltering, the Schwan’s man handing out frozen treats at the finish line was still the most popular guy on campus. Kids of course loved him too, and those who participated in the Bike Camp for Kids had a blast—an inspiring window into the future of cycling.

For more pictures from the event, check out our Facebook page and click here and here for even more rider portraits.

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