Explore the striking scenery and geology of the Columbia Gorge _ Oregon Field Guide

This whole thing is a result of the eruption of Mount Hood, 1782, and it filled up this whole valley. See, it continues on the other side. Anyone who travels knows the best tour guides are those who love their subjects. Where are we headed now, Scott? So we're heading out to Chanticleer Point. It's also called Women's Forum State Park. So we were delighted when geologist Scott Burns invited us to explore his favorite subject, the Columbia River Gorge. This is my favorite place in the gorge, right here. An interesting thing about the gorge is it's a story of two major floods. The first floods were from 14 to 16 million years ago. All of the basalt flows coming from eastern Oregon and filling up the area where the ancestral Columbia River was. One flow on top of another on top of another of basalt. So right over here we've got Vista House, and that whole promontory there is one basalt flow. One basalt flow. The basalt flow came in and filled up totally from the bottom all the way to the top with one flow and solidified. And that is the flow that formed this particular headland. Scott points out an intriguing difference between the two sides of the river. The Oregon side is straight up and down. The Washington side is very, very low angle going up. Flow on top of flow on top of flow of the Columbia River basalt. But the whole thing has been uplifted and then tilted to the south. So the whole Washington side, the tilted side, is all landslide. The Oregon side has all the waterfalls because it's straight up and down. Water comes out to the edge and comes over. The other story that we have here are the Missoula floods. Between 15,000 and 18,000 years ago, you had an ice dam that formed up in northern Idaho. And then all of a sudden that dam broke. It took three days for all the water to leave. And then that came down through Spokane across eastern Washington. All that water got back into the Columbia River. And it came down the gorge. Scott says these floods were the greatest known to have ever occurred in North America. And we're talking velocities coming out of the gorge at 50 to 60 miles an hour. Eroding things and big, huge boulders being bounced around on the bottom. We believe that there were 40 different floods that reached down here. And so they really had a significant effect on the gorge. And then way off in the distance, you can see Beacon Rock sticking up. And Beacon Rock is the heart of an old volcano. And the Missoula floods have really scoured it away. And so we call it a volcanic plug or volcanic neck. And why does that plug remain? Because it is very, very dense basaltic andesite. And it just doesn't weather very rapidly. The other thing is it's very young. And it's the youngest volcano in the whole Portland area. 55,000 years old. And so those are some of the things that we can see. Wow. Our route takes us along the old Columbia River Highway. And through some pretty tight turns. Good thing you can shoot and be in a car at the same time, Todd. Yeah. Let me know if you get car sick. All right. Well, we're almost through most of the hairpin curves. Lateral Falls is pretty close. Lateral Falls is my favorite falls. Oh, it is special. Well, it's got a good story. Oh, I can't wait to hear it. And the geology, yeah. I love hiking in here in the summertime. It's just wonderful. Lateral Falls is known for its beautiful columnar architecture, a characteristic of Basalt's multifaceted structure and the way it cools. This is another place where a flow has completely filled up a canyon. Can you see the round canyon? The lower part that we have got down here are columns. And what happens is the flow will stop. And when it stops, it cools from the top down and the bottom up. And as it does that, the rock forms a big crack because it shrinks. Sometimes four, five, six-sided shapes. And so all up and down the Columbia Gorge, you will see these beautiful Basalt columns. We use a lot of those columns in our gardens. And it is very northwest. So what is going on with that patch of lichen? Lichen is a symbiotic relationship of algae and fungus. So one has the house, one has the food. And so it's a marriage. And in fact, in the whole world, this is the only marriage on the rocks that actually works. Surprisingly, Scott's favorite feature here at Lotterell doesn't have anything to do with the falls. So this is the rock that I wanted to show you. It's completely different from all the other basalts. Primarily a volcanic rock we call dacite. And this is really the dome of an old volcano from 25 million years ago. We're just talking geology here. This is very interesting. Well, it is. Geology is always here. Very nice. You know what they say, geology rocks. Our next stop takes us to another spectacular waterfall. You know which one. We're at Multnomah Falls. And it is probably the most photographed place in the state of Oregon. And this really exemplifies the geology of the Columbia Gorge, especially on the Oregon side. You have a major waterfall. Also, you have got five to six major flows of the Columbia River Basalt. And the lower waterfall that we have right here is one flow, just filled up to that point. Then as you go up there are like three major flows, maybe four. And then up to the very, very top where it's really, really irregular, that's Pillow Basalt. That is where the actual flow flowed into a lake that was here at that particular time. This magnificent falls is also the site of a cautionary tale. Back in 1995, about halfway up just above Benson Bridge, a 400-ton piece of rock the size of a school bus broke off and fell into the plunge pool. And it was like a tsunami that went over the top of it. We can see remnants of that on the side of the plunge pool. So landslides and rockfall is very, very common here in the Columbia Gorge. Next stop is going to be Cascade Locks. What's at Cascade Locks? The Bridge of the Gods landslide. But it's actually a complex of a whole bunch of landslides that we have got across here. Back in approximately the year 1450, a large landslide broke away from the peak to the left and came all the way down across the Columbia River and dammed it up. Native Americans could cross from one side to the other side. And so they called it the Bridge of the Gods. There wasn't an area with water flowing underneath it, most likely. It was just a huge dam. And then eventually what happened is that landslide dam broke. And all of that water went catastrophically down into Portland. Probably a wall of water 50 feet high, wiping out probably many of the Native American villages that were along the river. You can still see remnants of the landslide. The little island that is right out in the middle of this area and then these big rocks that are sticking out. As we travel along the gorge... Oh, here comes the rain. Along with the change in the weather comes a change in vegetation. And we start losing the Doug Fir and Western Hemlock and start picking up the Ponderosa Pine. And then a dramatic change in landscape. Oh, wow. There's the Coyote Wall. Yep, there it is. There's the Coyote Wall. On the Oregon side, most everything is flat. All the bedding is flat. But on the Washington side, a lot of times it's tilted. And the reason is the whole Pacific Northwest is rotating in a clockwise manner. Oregon, for some reason, is rotating as a solid block and pushing into Washington. And all of southern Washington is being scrunched, squeezed together. And the flat-lying beds are now becoming tilted. And so when we look across the river, we can see these tilted beds. We're about 75 miles from Portland now. But the landscape is not getting any less dramatic. So this is where we're going to get off up here. Okay. We get off the interstate at Mosier and start climbing. So we're on the old highway, and we're heading to Tom McCall State Park and the Rowena Overlook. Wow. Yes, this valley here is just unbelievable. Here we are. Yep, Rowena Crest. Ah, gorgeous. We've arrived at the end of the gorge. Here, the landscape opens up to the high desert of eastern Oregon. Yeah, I love it. But this is the part of the gorge that everybody doesn't know about. You look on the other side, you can see layers of the Columbia River Basalt. And in fact, you go up the slope, and then all of a sudden, you lose them. And you have just nice, smooth, rounded hills that are up there. That's windblown silt. And so it tells us how high the Missoula floods got. And then as you start looking at those Columbia River Basalt flows, one on top of another, you go down, and all of a sudden, the flows are going like this. And then on the other side, they're flat again. What's going on there? Well, that's a fault. And so originally, you had rocks like this, and then if you pushed them, it goes down like this. And so you still have the flat ones on one side, but you have the other ones going down. These dramatic angle shifts in solid rock are another example of the powerful forces that shaped the Columbia River Gorge. If it seems like Scott knows pretty much everything about how all these features came to be, think again. I really want to look down onto these surfaces down here. Okay. And you can really see the differences, because the green versus the tan. Where did those come from? This is the mysterious part of this whole thing. There are areas that are very, very green, and then in between, it's dry. And if we go down to them, they're mounds, and they're called Mima Mounds. What caused them? For many, many years, we thought it's freeze-thaw processes. But then all of the glacial specialists from around the world got together, and they basically said, No, we don't like that. One of the current things is that the gophers caused it. I'm a believer in the earthquake hypothesis. If you take a piece of plywood, put sand all over it, and then hit it, what will happen is the sand will go into a whole bunch of little piles. And if you take this hard surface and have a big earthquake, what will happen is those loose sediments will form into piles. Whatever the hypothesis is of the day, they're intriguing. And that's another interesting story that we have in the area. And it's still a mystery. It's still a mystery.