Of Loess Piles and Hanging Pallets
Notes: This is my answer to Tipper's April Challenge at the M7
Challenge. It was:
"... No, you're doing it wrong. It's-" The older boy finished with an imitation of a wild turkey call. JD tried again.
The rest of the team snickered at the poorly done turkey call. Buck corrected him yet again, having him listen to how it should be done, before Vin interrupted. "Don't listen to him, kid. He's got it wrong hisself."
"Oh yeah? Then how come all those turkey hens came up to the other pit?"
"Figured that's 'cause a yer animal maggotism."
"Then you show us how it's done."
Ezra interrupted their squabble before it went any further. "Gentlemen, do you think that perhaps now is not the best time to be practicing your turkey calling skills. After all, as the sign on the last exhumed soil pedon we visited pointed out, our fowl feathered friends are currently in season."
"I believe the soil profile which we are to investigate can be found down the path directly behind Mr. Dunne."
"That's impossible, what fool wrote these directions?" Nathan pointed to the map and directions Professor Travis had given him. "The only thing to be found behind JD is the quarry!"
Understanding the truth to his comment, all of the college students followed the path around. They found themselves on a 30-foot high bedrock outcropping with a 15-foot loess cap looming above them. At the top of the pile of unweathered loess was the profile they were to judge. The only way for them to access the profile was a pallet hanging down the pit face, dangling from ropes that were tied to something at the top.
"Oh my," was all Professor Travis said, looking at the three foot ledge separating the edge of the bedrock from the face of the profile, which angled away from them towards the top. "Boys, be careful. I'm not sure if the university's liability insurance covers rock quarries. Let's do this as a group pit, following the contest times. Start in the pits for 10 minutes, out for 10, back in for 10 and then 30 minutes to finish. Who's writing?"
"Ezra is. JD, Nathan and Josiah need to shoot slope, then get ready to start to color and texture when the samples come out. Vin and Buck'll be up in the pit with me. We'll start pullin samples for horizons 1,3 and 4 and then find boundaries."
"Good plan. There are 5 horizons to a depth of 127 cm. The nail is at the boundary of the 3 and 4 at 56 cm. Ten minutes is starting now." Travis watched as the team started up, settling down into his camp chair for the hour.
The three who weren't going into the pit climbed up to the slope states to do their part. Ezra stood at the edge of the pit as the other three carefully climbed up the hanging pallet one at a time. As soon as the slope was taken care of Josiah, Nathan and JD were waiting with Ezra for the first set of samples. Above them the boundaries between the different horizons were being discussed and eventually Vin came down with the five different cups of the various samples.
"Well, maybe you should have done it yourself."
As they worked up the samples into texture balls, they could hear Chris and Buck calling down different answers to Ezra.
"Ez, mark no effervescence in the top two horizons, yes in the bottom three."
"Of course, Mr. Wilmington. Have you and Mr. Larabee decided on the structure for the first horizon yet?"
"Call it moderate granular," Chris' voice floated down from above them as Prof. Travis called the first 10 minutes. He and Buck slide down the loose soil of the cliff, joing the other five students on the wider part of the rock ledge.
"Call it moderate granular," Chris' voice floated down from above them as Prof. Travis called the first 10 minutes. He and Buck slide down the loose soil of the cliff, joining the other five students on the wider part of the rock ledge.
"What happened here?" He swept his arm across the landscape. "How did this get here?"
Chris could see Vin roll his eyes at the older student's more philosophical approach to the parent materials. But Josiah did have a point. If you understood just how the soil got where it was, you had a better handle on the parent material. Here it wasn't the problem it could be elsewhere, it was so obviously a loess cap that they were looking at.
He listened with one ear as he watched Buck explain the decisions they had made up in the pit to JD. The kid was new to soil judging, having been recruited by the older boy who had been his Introductory Soils lab TA. The soil profile they were looking at now was a bit easier than some of the others they had seen, the horizons clearly defined and such. That helped reinforce things with the younger student, boosted his confidence. Not that it really needed any major boosting, he was definitely picking things up fast.
"Chris looked up to see JD half running, half sliding down the loess pile. He held in his hand a ped from one of the horizons and was obviously excited over what he found. Between his momentum and the loose soil he didn't have a chance as he hit the rock ledge the others stood on and slid on over.
"JD!" Buck wasn't far behind him, yet a bit more careful, as was leaning over the edge of the cliff looking at him. He was joined by the others and Professor Travis. They all breathed a sigh of relief to see that he hadn't gone all the way down, managing to catch hold of a small shelf not far below them.
"Oh my," Professor Travis was looking decidedly green as he backed away from the edge. "Chris, Vin, get that pallet down from the profile face, we're going to need the rope. Josiah, do you think that you can pull him up?"
"I may need help, but we have seven people here, we should be able to get him back up."
"Umm, guys, can you hurry? I don't know how much longer I can hang on." JD's arms were getting tired, his fingers hurt and there were scrapes down his side from the fall that he didn't even want to think about. He already knew that Nathan was going to pester him to no end about his injuries, and knowing his luck he'd have to go to the hospital. And he hated hospitals.
It wasn't long before Chris and Vin had the ropes from the pallet dangling down the rock face near where JD hung. Digging his toes as far into two small cracks as he could, JD let go of his handholds to try to swipe at the rope. The first try was a miss, with him loosing his balance and sliding a bit further down. "Guys, you gotta get it closer to me, and lower."
Above him on the cliff top, Josiah looked at the little much abused rope. Now, as he held it in his hands, he could see the various weak spots from where it had been supporting the weight of numerous soil judgers for the last week. Praying that it would hold JD's weight while scraping against the limestone cliff, he shifted it closer to his young friend and let out a little more of the slack. He was rewarded with a pull on the rope when JD was finally able to latch on.
He could feel the line jerk in his hands, unsure of what was causing the movements until he heard Vin calling something down to JD. "Just relax and let Josiah pull ya up. Ya may think yer helping, but it makin' it harder for him."
The line stopped jerking, but Josiah could feel his muscles rebel against him, a quick nod to Nathan had the rest of the guys adding their strength to the line. A few long minutes later they could see a pair of hands and a dust-covered head at the edge of the cliff.
"Umm, guys, ya think ya can give me a hand?"
A sharp laugh from Buck was his reply. "Even with his life in danger, he's still a smart-ass."
Moments later found them all lounging against the pile of soil that they had been judging, Professor Travis angrily barking into his cell phone. They all cringed when he snapped it shut and swore loudly. Orrin Travis wasn't a man to get upset easily and this was not a good sign.
"I just got done speaking to Terry," he looked over JD one more time, not sure if he believed Nathan that he was just bumped and bruised. "He says there had been a safety rope at the edge of the cliff to prevent this happening."
"Yeah, I saw it," JD piped up and motioned to where he had been precariously hanging earlier. "It's down there."
Travis made himself count to ten before continuing. "Well, Terry sends his apologies and says he's going to close this practice pit. I say we're done for the day. Gather your stuff and let's head back to the hotel. Let's see if we can find something a bit less stressful to do back in Red Wing."
What is loess? (according to the USGS - http://pubs.usgs.gov/info-handout/loess/> )
Loess (pronounced "luss"), is German for loose or crumbly. It is a gritty, lightweight, porous material composed of tightly packed grains of quartz, feldspar, mica, and other minerals. Loess is the source of most of our Nation's rich agricultural soils and is common in the U.S. and around the world.
Although early geologists assumed loess was either fluvial (deposited by a river) or lacustrine (formed in a lake), today we know that loess was eolian (deposited by the wind). During the Ice Age, glaciers advanced down into the mid-continent of North America, grinding underlying rock into a fine powderlike sediment called "glacial flour." As temperatures warmed, the glaciers melted and enormous amounts of water and sediment rushed down the Missouri River valley. The sediment was eventually deposited on flood plains downstream, creating huge mud flats.
During the winters the meltwaters would recede, leaving the mud flats exposed. As they dried, fine-grained mud material called silt was picked up and carried by strong winds. These large dust clouds were moved eastward by prevailing westerly winds and were redeposited over broad areas. Heavier, coarser silt, deposited closest to its Missouri River flood plain source, formed sharp, high bluffs on the western margin of the Loess Hills. Finer, lighter silt, deposited farther east, created gently sloping hills on the eastern margin. This process repeated for thousands of years, building layer upon layer until the loess reached thicknesses of 60 feet or more and became the dominant feature of the terrain.
What does a loess look like?
What is Soil Judging?
The NC State team has posted pictures from last year's contest here:
Typical soil judging pit/profile -sort of
This is the type of thing we look at
Here are a few more soil profiles