Climate Change Is Moving Mountains

[Still Waters]

You've heard about how climate change can force trees, animals and fish to relocate when dealing with temperature shifts. But here's a new one for you. Climate actually helps move mountains and vice-versa: Mountains influence climate as well.

For millions of years, global climate shifts altered the structure and internal movement of mountain ranges, and in turn, the resulting development of glaciers and erosion has enabled mountains to alter the local climate around them.

http://news.discover...ains-151109.htm

[Doc Socks Junior]

No.

I was quite specifically told by several posters here that these processes are irrelevant to climate change.

But maybe even reading this heresy has infected me.

[Doug1029]

I was quite specifically told by several posters here that these processes are irrelevant to climate change.

In deep time, climate can influence mountains. But if we are trying to solve a climate-related problem, we can't exactly move a mountain to fix it; although, the coal industry is doing a magnificent job of moving mountains.

Climate change is only measurable with good records and the farther back we go, the poorer those records are. So unless the mountain has moved observably since about 1900, we wouldn't know it.

I have been studying the Ohio-West Virginia state line which mostly lies a few feet below the water surface along the north shore of the Ohio River. The shoreline was surveyed in 1786-87, so we know within a few feet where it was. There have been minor changes in the shore owing to deposition from creeks and the formation of a sand bar behind a sunken barge, but mostly, the alluvial fans and sand bars are still where they were 227 years ago, but because navigation dams have raised the water level, the shoreline is now several feet under water. If two centuries of floods (including the Johnstown Flood) have been unable to make significant changes in the Ohio River, what changes would we expect to see in a mountain during that time (St. Helens excluded)?

Doug

[Doc Socks Junior]

In deep time, climate can influence mountains. But if we are trying to solve a climate-related problem, we can't exactly move a mountain to fix it; although, the coal industry is doing a magnificent job of moving mountains.

They are. Sometimes there are positives (see below). Although the orange river in the town below (I think due to the exhumation of some crazy iron concretions) wasn't nice.

Climate change is only measurable with good records and the farther back we go, the poorer those records are. So unless the mountain has moved observably since about 1900, we wouldn't know it.

There was a 14 m uplift event in 1899 according to the paper being written about. But that was more due to the tectonics of the region. Which they're currently tracking with GPS. 40 mm/yr of convergence (Elliot et al., 2010). Seems observable to me. Julie Elliot does interesting work with how GIA affects tectonic interpretation, and indeed, tectonics in the area.

I have been studying the Ohio-West Virginia state line which mostly lies a few feet below the water surface along the north shore of the Ohio River. The shoreline was surveyed in 1786-87, so we know within a few feet where it was. There have been minor changes in the shore owing to deposition from creeks and the formation of a sand bar behind a sunken barge, but mostly, the alluvial fans and sand bars are still where they were 227 years ago, but because navigation dams have raised the water level, the shoreline is now several feet under water. If two centuries of floods (including the Johnstown Flood) have been unable to make significant changes in the Ohio River, what changes would we expect to see in a mountain during that time (St. Helens excluded)?

200 years at 250 million tons of sediment per year types of changes. Granted, small potatoes comparative to their total mass and all that, but still.The erosion in the St. Elias is mostly glacially-caused, so interesting effects arise there.

Also, that's the beauty of well-evolved river systems in stable continental interiors.

[Doug1029]

They are. Sometimes there are positives (see below). Although the orange river in the town below (I think due to the exhumation of some crazy iron concretions) wasn't nice.

There was a 14 m uplift event in 1899 according to the paper being written about. But that was more due to the tectonics of the region. Which they're currently tracking with GPS. 40 mm/yr of convergence (Elliot et al., 2010). Seems observable to me. Julie Elliot does interesting work with how GIA affects tectonic interpretation, and indeed, tectonics in the area.

What climate changes were observed in association with the tectonic events?

200 years at 250 million tons of sediment per year types of changes. Granted, small potatoes comparative to their total mass and all that, but still.The erosion in the St. Elias is mostly glacially-caused, so interesting effects arise there.

What climate changes have been associated with the glacial erosion?

Also, that's the beauty of well-evolved river systems in stable continental interiors.

Turns out the Ohio/Alleghany River system has an interesting history. The ice sheets dammed northward flowing rivers, diverting their waters. These overflowed intervening ridges and washed them out, creating the modern Ohio. Happened in several different locations.

Here's a question for the geologist: the glaciers extended south of the Ohio River into Kentucky. There should be an old river channel at the south edge of the moraine. But I have been there and looked. There is no old channel. Why is that? How did the Ohio River get past the glacier? Even if it flowed over or under the ice most of the time, there should still have been a channel.

Doug

[Doc Socks Junior]

What climate changes were observed in association with the tectonic events?

Changes in atmospheric flow patterns and precipitation.

What climate changes have been associated with the glacial erosion?

Changes in atmospheric flow patterns and precipitation. Feedback mechanisms mean the tectonics affect the glacial erosion affect the climate and so on and so forth. You could read the paper. It's an interesting interplay.

Turns out the Ohio/Alleghany River system has an interesting history. The ice sheets dammed northward flowing rivers, diverting their waters. These overflowed intervening ridges and washed them out, creating the modern Ohio. Happened in several different locations.

Here's a question for the geologist: the glaciers extended south of the Ohio River into Kentucky. There should be an old river channel at the south edge of the moraine. But I have been there and looked. There is no old channel. Why is that? How did the Ohio River get past the glacier? Even if it flowed over or under the ice most of the time, there should still have been a channel.

I'm going to need slightly more context for this question. Which glaciers? Pre-Illinoian? Illinoian? Wisconsinan? Where in Kentucky? Which moraine?

I think I actually have the answer to your question, but we'll see.

[Doug1029]

I'm going to need slightly more context for this question. Which glaciers? Pre-Illinoian? Illinoian? Wisconsinan? Where in Kentucky? Which moraine?

I think I actually have the answer to your question, but we'll see.

I don't know which glacier, but Illinoian seems to be the guilty party in most of the stream/river diversions in the area. The location was just west of Florence, Kentucky. I don't know which moraine by name, but it was at the most-southerly edge of the glaciated region, right up against unglaciated hills.

I just thought of a possible explanation: if the ice had created a temporary lake that over-flowed a divide farther south, the river would have had a way around the glacier without leaving a channel up against the ice sheet. That channel could not have been occupied for very long, else it would have eroded out and become the permanent course of the river.

On another question: I notice in many of the piedmont deposits in the Front Range and San Juans that Illinoian-age glaciers tended to have long narrow beds compared to other glaciers. Was there something different about the physical properties of Illinoian-age ice that caused it to behave differently? Maybe colder climate created harder ice, or something like that?

Doug

[Doug1029]

I don't know which glacier, but Illinoian seems to be the guilty party in most of the stream/river diversions in the area. The location was just west of Florence, Kentucky. I don't know which moraine by name, but it was at the most-southerly edge of the glaciated region, right up against unglaciated hills.

I just found a map that shows that area as pre-Illinoian moraine.

Doug

[Doc Socks Junior]

I don't know which glacier, but Illinoian seems to be the guilty party in most of the stream/river diversions in the area. The location was just west of Florence, Kentucky. I don't know which moraine by name, but it was at the most-southerly edge of the glaciated region, right up against unglaciated hills.

I concur. The Illinoian did have the biggest impact on the present drainage pattern. The pre-Illinoian (Kansan) was a modifier also. Wisconsan did a little, but wouldn't have left deposits that far.

I just found a map that shows that area as pre-Illinoian moraine.

So...a decent possibility is that the channel existed, but the Illinoian wiped out evidence from it.

I just thought of a possible explanation: if the ice had created a temporary lake that over-flowed a divide farther south, the river would have had a way around the glacier without leaving a channel up against the ice sheet. That channel could not have been occupied for very long, else it would have eroded out and become the permanent course of the river.

That seems reasonable. I think it all comes down to that identification of the age of the moraine (which you found). I think the overprint of the Illinoian, the latest and greatest effect (discounting minor Wisconsan effects) is why you don't see the channel.

On another question: I notice in many of the piedmont deposits in the Front Range and San Juans that Illinoian-age glaciers tended to have long narrow beds compared to other glaciers. Was there something different about the physical properties of Illinoian-age ice that caused it to behave differently? Maybe colder climate created harder ice, or something like that?

Mmm, yeah, climate differences were present I believe. I don't know about the harder ice, maybe a precipitation effect though. Could be less ice, didn't spread out as much, so a narrower channel? Or something to do with what the surface they were on differing between glaciations...easier to wear away old till then consolidated rock, so it coulda stayed in a relatively narrow channel...

So maybe a surficial geology difference rather than ice property difference.

I'm spitballing.

[Doug1029]

I concur. The Illinoian did have the biggest impact on the present drainage pattern. The pre-Illinoian (Kansan) was a modifier also. Wisconsan did a little, but wouldn't have left deposits that far.

I found some more articles. Lakes Monongahela and Tight were of Nebraskan age. There was another lake between Lake Tight and Cincinnati, but I haven't been able to find its age. The temporary channel around Cincinnati was of Illinoian age (The blockage just below Cincinnati was mostly ice, not moraine.). There were two or three more lakes down river, but I don't know their ages. The Teays diversion was mostly in Nebraskan time, but later readvances reworked the topography. Part of the old Teays system still exists in open air in southern Ohio and West Virginia - you can see it south of Chillicothe on Google Earth. The rest is buried under ground moraine.

The Late Wisconsinan rerouted the Finger Lakes into the Alleghany. There were also two more valleys that were blocked by ice at the north end and temporarily diverted to the Alleghany drainage. And there was a third one that was permanently reversed into the Alleghany. The Alleghany was dammed by a surge of ice, but apparently the river found its way past along the ice front; there was an ice lake just upstream of it that had free-floating ice bergs. The moraine that now blocks the former channel at New Castle, PA is younger, so apparently the one that diverted the river in Nebraskan time is buried to the northwest under more recent till. Also, there were two or three rivers that used to drain northward that were diverted into the Ohio by moraines.

That seems reasonable. I think it all comes down to that identification of the age of the moraine (which you found). I think the overprint of the Illinoian, the latest and greatest effect (discounting minor Wisconsan effects) is why you don't see the channel.

I didn't see the channel because I wasn't looking in the right place. It's still there.

Doug