The Mysteries of the Newberry Caldera

Transcript

Dirty Freehub 0:20
This podcast is reproduced with the permission of KPOV Bend oregon.

KPOV 0:26
The following conversation with Ranger Randy and Dr. Daniel McKay, geologist and instructor at the University of Oregon, aired in 2018 on the Sasquatch Hideaway as a series on KPOV of Radio 89 FM Bend, Oregon. In this segment, we’ll hear about the features of the Newberry Caldera. We will answer questions like were there multiple calderas? How was Obsidian formed? Are pumice, obsidian and granite really the same. And what is the science behind geothermal energy?

Ranger Randy 0:57
A lot of stuff out of the Newberry caldera. So I understand there was more than one caldera creating event.

Dr Daniel McKay 1:04
Probably. So we know there was one caldera creating event because we can see the caldera, but there is also a volcanic rock that was produced during that eruption called a welded tuff. And welded taps are produced during highly explosive eruptions. And so it’s not surprising that we have this welded tuff. That’s the same age as the caldera. It’s kind of how we’re able to date when the caldera forming eruption occurred. But there are a couple of other welded turfs at Newberry Volcano that suggest that maybe there were previous caldera forming eruptions prior to the one about 75,000 years ago. So 75,000 years ago, we know there was a caldera forming eruption. We can point to the world at stuff that was produced during that eruption. There’s also ash, a lot of ash that was produced during that eruption, and that ash was very widespread. It has been found in the San Francisco area. So we know that was a highly explosive eruption, similar to how we can piece together that story 75,000 years ago. We can also look at these older welded tops and we don’t know for sure that they were associated with a caldera forming eruption. But it is it is likely. And then mapping detailed mapping at Newberry Volcano, there is the USGS, The US Geological Survey has done mapping at Newbury and some of that detailed mapping shows that there might actually be some older caldera walls that that weren’t produced 75,000 years ago. They were older than that. So one caldera forming eruption tends to be pretty destructive and it kind of destroys whatever was existing there before that. But by very careful mapping, we can kind of look in and find what might have been an older caldera wall. And some of the geologists at USGS who have been doing that mapping that they see evidence of older caldera forming eruptions, perhaps three different caldera forming eruptions that the result of that work will be published in a new geologic map of Newberry Volcano, probably in 2019. So we can expect to see the result of all of that work fairly soon. Wow.

Ranger Randy 3:13
Very exciting.

Dr Daniel McKay 3:14
Yeah.

Ranger Randy 3:15
The big obsidian flow that’s the most recent eruption, basically. Or, you know, lava.

Dr Daniel McKay 3:21
Of a of a lava flow like that. Yes. The big obsidian, PLoS 1300 years old. There was an eruption at Mount Hood. More recent than that. And it did produce the volcanic rock. But it wasn’t a lava flow like what we see at the big obsidian flow.

Ranger Randy 3:37
So what is obsidian?

Dr Daniel McKay 3:38
Yeah, so obsidian is a very glassy rock. I think that that’s intuitive to everyone who has seen Obsidian. It looks like glass and it is essentially glass. Window glass is mostly silica and it doesn’t have a crystal structure. So most volcanic rocks, when that rock cools, it forms crystals and and obsidian didn’t form any crystals when it cooled. And it is also mostly silica. So it really is very similar to window glass. Window glass, of course, is manmade and obsidian is a natural product, but because it lacks a crystal structure, it really is truly glass, volcanic glass. And a lot of times the reason that volcanic glass forms is that the lava was quenched or cooled so rapidly that crystals didn’t have any time to form. So that’s one thought for how Obsidian Forms is it’s just very rapid cooling. But if you go and visit the big obsidian flow, it’s a very thick lava flow, hundreds of feet thick. There’s a staircase that gets you up to what appears to be the top of the lava flow. But as you hike around, you see that it actually isn’t the top of the lava flow. It is even higher than that trail that goes through the lava flow. So it’s hundreds of feet thick. We don’t know if there’s obsidian all the way through, but there is there is quite a bit of obsidian in that lava flow. And it seems unlikely that it all cooled very quickly. We talked about how rock is a very good insulator. And so in the interior of that lava flow, it wouldn’t have been cooling very quickly. So another way that volcanic glass can form is if the lava itself is so sticky or pasty or viscous and discuses a term that it just that describes how materials flow. So if something doesn’t flow very easily, it’s very sticky or pasty, then it’s highly discussed that the type of lava flows that form obsidian are very scarce. Some of the most viscous types of lava flows on earth. So if it’s very sticky, very pasty at the molecular level, if you think about crystals forming, in order for crystals to form, atoms have to be able to move to form bonds because crystals are are a network of atoms that are all bonded together in a very specific way. So if the material itself that those atoms are in is so sticky, so viscous, that the atoms can’t even move very easily, then you might get a glass forming. So that’s another idea as to why Obsidian formed. Perhaps it cooled very quickly, or perhaps it was such a vicious fluid that when it was molten that it just couldn’t form crystals.

Ranger Randy 6:22
To become that this distance would have to have more silica.

Dr Daniel McKay 6:25
Yeah. So lava flows, the viscosity or the stickiness of lava flows is directly related to the silica content. So the lava flows that we have been talking about at the lava cast forest and Lava Butte lava river cave, those are low silica lava flows and that’s why they’re able to just flow across the landscape. And like what you see in Hawaii, those are also low silica lava flows. But if the silica content is higher in the basket, viscosity is also higher. So the big obsidian flow was a high silica lava flow, which meant that it was very vicious.

Ranger Randy 7:01
So how does magma become full of silica?

Dr Daniel McKay 7:05
The most magma has has a high percentage of silica. So something that is a low silica lava flow like lava blue or a lava cast for I’m calling it a low silica lava flow. Geologists call that low silica, but it’s really about 50% silica. So silica is in most magma to start with. But what we call a low silica magma or a low silica lava is about 50%. A high silica magma or a high silica lava is 70, 80%, maybe silica so much higher. And the way that something goes from a low silica magma to a high silica magma is a whole subject of of scientific inquiry and kind of figuring out all the different ways, all the different things that can happen to Magma to make it evolve. We call that process an evolution, because when magma originates from deep in the earth, it is a low silica magma. Magma ultimately comes from the mantle of the earth. And if you melt part of the mantle and generate magma, it’s going to be a very low silica magma. So that’s the ultimate source of of all magma. But we know that not all volcanoes erupt, low silica magma. So something has to happen to it on its way to the surface. And the crust of the earth is very different in chemical composition than the mantle of the earth. So if we have some magma that’s generated in the mantle, it rises up and it kind of gets stuck in the crust for a while. It can melt some of the crustal rocks. It can change in chemical composition either by melting crustal rocks or just by slowly cooling as it’s sitting there in the crust. Its cooling crystals are forming. Those crystals settle down to the bottom of the magma chamber, and that changes the chemical composition of the rest of the molten material. So all these different things can happen to the magma between when it’s generated from the mantle and when it’s erupted out of a volcano. Those changes have big impacts on how much silica is in the magma.

Ranger Randy 9:00
So that makes it sound like silica is has a low melting point.

Dr Daniel McKay 9:06
It does, yeah. Silica in relative to, you know, other. Yeah. Yeah. The other elements that are in magma, if you kind of take the most common elements silicon and oxygen which together make silica have one of the lower melting point.

Ranger Randy 9:23
So that’s how it can build up to a higher percentage.

Dr Daniel McKay 9:26
That’s part of the reason cause yeah, yeah, yeah. If it’s melting. So if a magma chamber, if, if there’s a body of magma in the crust and it’s melting the rock around it. Yes. That is part of the reason that the silica that’s in that rock has a lower melting temperature. If that rock was all iron, that magma wouldn’t be able to melt it as easily. So, yes, part of the reason is that silica has a low melting point, but there are a lot of other reasons why magma can evolve.

Ranger Randy 9:51
Because heavier particles like the iron then precipitate out.

Dr Daniel McKay 9:54
Yes.

Ranger Randy 9:54
Yeah, I get it. Yeah.

Dr Daniel McKay 9:55
Think you.

Ranger Randy 9:57
Get closer. Explain how pumice happens.

Dr Daniel McKay 10:00
Yeah. So if we have a magma chamber underneath Newbury and it’s very high in silica, let’s say it has sat there underneath Newbury, changing and evolving for quite some time. So it’s a very high silica magma chamber and interrupts. The early parts of that eruption will have a lot of gas. Gas, that’s what’s driving the eruption. So the gases that are dissolved in magma are carbon dioxide, sulfur dioxide, so CO2 and CO2 and then water H2O is a very common gas. It’s dissolved in magma. So it’s those gases coming up towards the surface that drive the eruption and gases lead to an explosive eruption. So we have this high silica magma and it’s full of gas and the gas is expanding as it comes up towards the surface. And so the result of that eruption is pumice. We see all those bubbles or vesicles in pumice. That’s where the gas was. And there was so much gas that it just left a very thin wall around the bubbles of of glassy material, which was the magma. And that cooled very quickly on its way up out of the volcano. So by the time it was ejected out of the volcano, it was this solid piece of pumice with these holes left behind from the gas. So pumice is is always a result of a very explosive eruption or a lot of gas. So pumice was produced during the eruption that created the big obsidian cloud. So 1300 years ago there would have been this highly explosive eruption of gas and ash and pumice blasting up into the sky. If we were here to see it, we would have seen this eruption column, kind of like the Mount St Helens eruption, but perhaps even going up higher into the sky. And that’s blasting out pumice and ash. That ash was blown all the way to Idaho. So it was a fairly explosive eruption. Once most of the gas was gone, there was still enough gas to get a lava flow to come out of the ground. But now it’s not blasting into the atmosphere. There’s not as much ash ash produced. There isn’t as much pumice produced. Instead, you just get this oozing, highly vicious but still oozing lava flow. But the chemical composition of that obsidian, this is the big obsidian flow that’s erupting. The chemical composition of the obsidian is identical to pumice. So chemically they’re the same thing. It’s just the pumice was created during the more gassy, explosive phase of the eruption and the obsidian was created during the less gassy, more flowing phase of the eruption flowing in terms of just oozing out of the volcano instead of blasting out of the volcano.

Ranger Randy 12:36
So it’s possible to get up pumice eruption without actually getting obsidian.

Dr Daniel McKay 12:41
It is possible, yes. If everything if it’s a lot of gas and everything is sort of blasted highly explosively out of the volcano and you’ll just get pumice. Most volcanoes tend to have a more quiet, effusive or oozing phase after eruptions. So it’s possible for an eruption to only produce pumice, but most of them produce pumice and then later on they produce more dense, glassy material.

Ranger Randy 13:05
So that if it cools slowly, then it could be real light rather than.

Dr Daniel McKay 13:09
Obsidian. Yeah, if it cools slowly, it could be right. Rayleigh is is a term for volcanic rock that’s high in silica. Pumice is high in silica, obsidian is high in silica they are both rhyolite, but they are special types of rhyolite with a special texture. Another high silica rock that a lot of people are familiar with is granite. And granite is actually chemically identical to the pumice and the obsidian. It’s just it never came out of a volcano at all. So if we think about that magma chamber that fed the big obsidian flow eruption, that eruption first had an explosive phase that produced pumice and ash then, and it had an effusive or oozing phase that produced the big obsidian flow of some of the material probably that never left the magma chamber. And it is down there cooling very slowly underneath the volcano that will form granite. So pumice, obsidian, granite, chemically, they’re all the same thing. They could come from the same magma chamber, but their textures are very different depending on how they cooled.

Ranger Randy 14:07
So the other question we have always is that we have this volcano, we have heat. So how do we develop the geothermal?

Dr Daniel McKay 14:16
Yeah, so, so volcanic areas, they’re they’re generally as heat because down there somewhere there’s magma or there’s hot rock. So the heat is there in volcanic areas. But you need two other things in order to have geothermal potential in the in terms of generating electricity. So that’s called a geothermal reservoir. And a reservoir in this sense of the word doesn’t mean like a big underground lake or anything like that. It just means an area where energy can be produced. So the things you need for a geothermal reservoir are the heat, and volcanoes provide that. You also need water because it’s water that is taken out of the ground and run through turbines. And it’s the turning of those turbines that generates power. So in order to produce geothermal energy, you have to have hot water. So the volcanoes provide the heat. The water usually comes from groundwater. So you have, you know, maybe rain and snow that percolates into the ground. It at that point is groundwater and it gets heated up by the heat source, which is volcanic ultimately in nature. So in order for the heat to be transferred from the rock to the water, you need to have fractures or cracks in the rock. If you don’t have fractures in the rock, the water can’t percolate down where the heat is. So those are the three things you have to have to have a geothermal reservoir or just the potential to produce geothermal energy. So hot rock water and fractured rock and the fractures really are important. Usually these are really very small fractures in the rock. So when the water percolates down through there, through these tiny fractures, there might just be hairline cracks. That water can actually absorb quite a bit of the heat from the rock. If you had a big crack in the rock, that was, you know, maybe a foot wide, you’re not going to transfer much of that heat to the water at all because the water just is going to rush through that area and cracks a foot wide don’t really exist at depth. But just for the kind of the mental image of what you need to transfer heat to water is these very tiny, tiny fractures. So volcanic areas like Newbury have heat. We know that Newbury is an active volcano. It’s not actively erupting right now, but it is capable of erupting again in the future. We know there’s a heat source down there. We can drill wells through the rock layers and we can measure the temperature of that rock. And it’s very hot there are fractures in some of the rocks in Newbury, but not in others, which means that hot water exists in some parts of the region, but not in others. And so it’s really the fractures that really determine where geothermal energy could be produced.

Ranger Randy 17:01
And they have been very successful so far up there, as my understanding.

Dr Daniel McKay 17:04
Right. There’s been a lot of geothermal exploration at Newbury, and actually it was geothermal exploration that kind of initiated designating parts of the volcano as a monument. And that was in part to protect a region of the volcano from geothermal development. So it is a national monument. And within the monument boundary there is no exploration for geothermal energy. But outside of the monument boundary, there is. And so there are ongoing projects where they drill down and and look for potential for producing geothermal energy. None of those projects have been successful yet. But the last big project that occurred there was really not so much to develop geothermal energy, but to develop a technology where you if you have hot rock but it isn’t fractured, you could create your own fractures in the rock and then pump water down and create a geothermal reservoir. So remember, if we have hot rock and we have water, but there’s no fractures in the in the rock, it doesn’t do us any good. So this was a project where the fractures were actually developed and then the water was pumped down to create a geothermal reservoir. And that type of research is really important to the future of geothermal energy. Geothermal energy offers a huge potential for very clean, renewable energy. So if we can figure out how to fracture rock and create geothermal energy in places maybe where volcanoes don’t even exist, that could open up geothermal energy as an energy resource in non volcanic areas, which might be a good way to move from fossil fuels to a form of energy that doesn’t produce CO2. Geothermal power plants have a very small footprint. Some people do consider them an eyesore because they can have cooling towers, which then release steam into the atmosphere. But they don’t all have to have that. There are geothermal power plants that use a different mechanism of of getting the heat from the water, and they don’t require the cooling towers. So in that instance, there’s it’s really very little ice or at all associated with it. And the footprint of of producing that energy is the size of the geothermal power plant, which is much smaller than acres and acres of windmills, which also have impacts on wildlife and um, and other impacts on the people who live in those areas.

Ranger Randy 19:31
This is kind of out of your area, but there’s always questions about hydrology. So where does our water come from? I mean, since this is all rock, we don’t have aquifers per say, but we do have really great water.

Dr Daniel McKay 19:44
Yeah, so we do have great water and we do actually have aquifers. A lot of times if you are looking at, you know, what is an aquifer, maybe in a textbook or something like that, it’s it’s shown as maybe sand or gravel. So there’s a layer underneath the surface of the earth that sand or gravel and water can move very easily between the grains of sand or gravel. So sand and gravel make great aquifers and that just means that all of the space between each little grain of sand or each piece of gravel, all of that space is occupied by water. It doesn’t mean that there’s an underground river flowing through, you know, a certain area, the sand or the gravel. It just means that whole entire deposit of sand and gravel is saturated with water. So it’s kind of like a sponge we do in central Oregon. There are some layers beneath us that are sand or gravel. There’s also a lot of lava flows. There’s a lot of volcanic rock and volcanic rock, especially basalt lava flows are very good aquifers. They are fractured. So there is open space in there. And if rain and snow fall on a, say, a basalt lava flow, that water isn’t going to flow across the lava flow like a river. Instead, it’s just going to percolate right down into the lava flow. So the lava flow itself becomes an aquifer that rain and snow doesn’t become a river or a stream or a lake. Instead, it just goes right into the ground and it flows through the lava flow as groundwater. So since we have so many very recent lava flows in central Oregon, we actually do have a lot of groundwater in central Oregon. And and roughly of all the rain and snow that falls in a given year, roughly two thirds of that ends up in the ground as groundwater and about one third ends up in the Deschutes River and the other rivers in central Oregon. So we do have quite a bit of groundwater in the area because we have porous young volcanic rock that’s full of fractures and is just makes a great aquifer.

Ranger Randy 21:41
What causes it to come to one spot and emerge as a river?

Dr Daniel McKay 21:46
Yeah. So we also have a lot of springs in central Oregon and we have places in central Oregon where full rivers emerge as springs, Anatolia River does this. There are parts of the Mackenzie River that do this. So that is when an aquifer, so water that is traveling underground comes to the surface. When that aquifer intersects the surface, that’s what we call a spring. So if you picture a lava flow on the surface of the earth and up high at high, this lava flow is maybe starting up in the mountains and kind of going downhill up high where there’s a lot of rain and snow that falls. All that water percolates directly into the lava flow. It flows through the lava flow. And when it gets to the base of at the end of the lava flow downhill, it emerges as springs at the base of the lava flow. And almost all the springs in central Oregon, if you’re at a place where you see these beautiful springs emerging from a hillside, look at the rock and it most likely it’s going to be a lava flow and that is an aquifer that happens to be a lava flow. There’s water flowing through the lava flow and you happen to be at the end of that lava flow. And so all that lava is is coming out of the lava flow. Another place where this could happen is a fault if a fault kind of offsets the lava flow. So that part of it is lower than the rest, then the groundwater can emerge as springs.

Ranger Randy 23:07
So does it work? Kind of like on us as it does on the surface? I mean, we if you have all these cracks and all this water perking down everywhere, what makes it converge into that one spot?

Dr Daniel McKay 23:18
Oh, well, it might not just be that one spot. You see it coming out as a spring, but oftentimes there are multiple springs all along the edge of the lava flow. So if you really explore the area, you’re probably going to find a lot of other springs. And in a lot of cases here in central Oregon, our rivers are spring fed. So the Deschutes is a spring fed river. The metal is is a spring fed river. In some places you can actually see the springs feeding that river, but in many cases, the springs are below the water line in the river itself. So there really are multiple places where lava is coming out of the base of a lava flow, but sometimes it’s under water so we can’t see it. Sometimes vegetation soaks up all of that water and it doesn’t actually flow as a spring because it’s all getting used by plants. So you might come across an area where you think that it should be a dry area, but you’re seeing vegetation that really likes a lot of water. That is technically a spring. It’s just not flowing because the plants are consuming it all. But if you’re interested in geology, there are so many places in central Oregon that you can visit. A Newberry National Volcanic Monument is one really great place to go and see such a diversity of volcanic landforms. But also there is a fairly new organization that has formed in central Oregon called the Central Oregon Geoscience Society, and it’s a nonprofit. Its main goal is to provide geologic to field trip geologic education to the community. So if you’re interested in geology and you want to attend some talks that are focused on geology, check out the website for Central Oregon Geoscience Society. And we have free talks for the public once a month.

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