WEBVTT 99:59:59.999 --> 99:59:59.999 Okay, so this is the difference between uh, glacial till, 99:59:59.999 --> 99:59:59.999 which is unstratified, 99:59:59.999 --> 99:59:59.999 and non-glacial till. 99:59:59.999 --> 99:59:59.999 So, hopefully you can see that this uh, gravel here 99:59:59.999 --> 99:59:59.999 is well-stratified. 99:59:59.999 --> 99:59:59.999 There are a lot of sedimentary features here. 99:59:59.999 --> 99:59:59.999 Um, you can see graded bedding. 99:59:59.999 --> 99:59:59.999 You can also see cross bedding. 99:59:59.999 --> 99:59:59.999 Maybe I can just sort of zoom in on that. 99:59:59.999 --> 99:59:59.999 So there's cross bedding right there. 99:59:59.999 --> 99:59:59.999 Very coarse uh, cross bedding. 99:59:59.999 --> 99:59:59.999 However, the stratification or the horizontal layering, 99:59:59.999 --> 99:59:59.999 the general horizontal here, 99:59:59.999 --> 99:59:59.999 indicates that this is not glacial gravel. 99:59:59.999 --> 99:59:59.999 Even though it's approximately the correct size 99:59:59.999 --> 99:59:59.999 and sorting distribution. 99:59:59.999 --> 99:59:59.999 The presence of sedimentary features 99:59:59.999 --> 99:59:59.999 as well as uh, the stratification, 99:59:59.999 --> 99:59:59.999 that's the horizontal layering, 99:59:59.999 --> 99:59:59.999 indicated as not glacial gravel. 99:59:59.999 --> 99:59:59.999 Okay. I'll try and show you glacial gravel a little later. 99:59:59.999 --> 99:59:59.999 So this is uh, glacial till. 99:59:59.999 --> 99:59:59.999 It is gravel that is deposited by a glacier. 99:59:59.999 --> 99:59:59.999 Um, and the identifying characteristics of it 99:59:59.999 --> 99:59:59.999 is well-rounded clasts, 99:59:59.999 --> 99:59:59.999 however they're not really really well-rounded. 99:59:59.999 --> 99:59:59.999 They are definitely rounded to some extent. 99:59:59.999 --> 99:59:59.999 Um, oftentimes there are striations on each individual clast, 99:59:59.999 --> 99:59:59.999 maybe I can show you that later. 99:59:59.999 --> 99:59:59.999 Um, those are scratches that are produced 99:59:59.999 --> 99:59:59.999 when gravel bounces or scrapes against 99:59:59.999 --> 99:59:59.999 other pieces of gravel or the bedrock. 99:59:59.999 --> 99:59:59.999 And the other identifying characteristic 99:59:59.999 --> 99:59:59.999 is that the gravel itself is unstratified. 99:59:59.999 --> 99:59:59.999 There is no layering, no horizontal stratification. 99:59:59.999 --> 99:59:59.999 Um, and there really are no sedimentary features here, 99:59:59.999 --> 99:59:59.999 other than the lack of sedimentary features, 99:59:59.999 --> 99:59:59.999 which indicates that it was deposited by a glacier. 99:59:59.999 --> 99:59:59.999 Now hopefully you'll be able to see, 99:59:59.999 --> 99:59:59.999 if it'll focus on that, 99:59:59.999 --> 99:59:59.999 the scratches on the surface of this clast. 99:59:59.999 --> 99:59:59.999 Those parallel scratches are glacial striations, 99:59:59.999 --> 99:59:59.999 which are present on a clast. 99:59:59.999 --> 99:59:59.999 It's stuck in there pretty hard. Argghh. 99:59:59.999 --> 99:59:59.999 It won't come out. 99:59:59.999 --> 99:59:59.999 And in addition to the lack of uh, sedimentary features, 99:59:59.999 --> 99:59:59.999 um, one of the characteristics that you always look for 99:59:59.999 --> 99:59:59.999 is a very very poor degree of sorting 99:59:59.999 --> 99:59:59.999 in terms of clast size. 99:59:59.999 --> 99:59:59.999 And so, maybe I can zoom in on that a little bit. 99:59:59.999 --> 99:59:59.999 You've got clasts of all different, uh, sizes. 99:59:59.999 --> 99:59:59.999 Very poorly distributed. 99:59:59.999 --> 99:59:59.999 I suppose even down to these sizes, 99:59:59.999 --> 99:59:59.999 which have fallen down from the cliff face, I suppose, 99:59:59.999 --> 99:59:59.999 the gravel face anyways. 99:59:59.999 --> 99:59:59.999 Very poor sorting. 99:59:59.999 --> 99:59:59.999 Okay. Since we're talking about till, 99:59:59.999 --> 99:59:59.999 I thought I'd show you what happens when till, um, 99:59:59.999 --> 99:59:59.999 becomes a rock, when it comes consolidated or indurated. 99:59:59.999 --> 99:59:59.999 This is called tillite, which is uh, 99:59:59.999 --> 99:59:59.999 the rock, I suppose, from glacial till, a conglomerate. 99:59:59.999 --> 99:59:59.999 This one is very old. 99:59:59.999 --> 99:59:59.999 It is on the side of the Trans Canada, here. [cars going by] 99:59:59.999 --> 99:59:59.999 As you can tell by the traffic. 99:59:59.999 --> 99:59:59.999 And it is south of Wawa in Ontario, Canada. 99:59:59.999 --> 99:59:59.999 [traffic in background] 99:59:59.999 --> 99:59:59.999 This particular crop has been highly metamorphosed, 99:59:59.999 --> 99:59:59.999 so these in the Canadian shield. 99:59:59.999 --> 99:59:59.999 Um, so strongly metamorphosed. 99:59:59.999 --> 99:59:59.999 And this tillite is uh, weathering very rapidly 99:59:59.999 --> 99:59:59.999 as a result of the intense metamorphism, 99:59:59.999 --> 99:59:59.999 which has caused cracks and fractures 99:59:59.999 --> 99:59:59.999 which increase surface area, of course, 99:59:59.999 --> 99:59:59.999 and cause weathering to accelerate. 99:59:59.999 --> 99:59:59.999 [traffic in background] 99:59:59.999 --> 99:59:59.999 Now realize I'm looking at a shadow here, 99:59:59.999 --> 99:59:59.999 but hopefully you can see that the clasts are well-rounded. 99:59:59.999 --> 99:59:59.999 Very poorly sorted, in terms of size distribution. 99:59:59.999 --> 99:59:59.999 And are not layered. They are unstratified. 99:59:59.999 --> 99:59:59.999 I just thought you might want to see what's on the other side of the road. 99:59:59.999 --> 99:59:59.999 That is Lake Superior, 99:59:59.999 --> 99:59:59.999 about an hour south of Wawa, Ontario. 99:59:59.999 --> 99:59:59.999 Pretty big lake, eh? Kind of looks like the ocean. 99:59:59.999 --> 99:59:59.999 You can't see the other side of Lake Superior, 99:59:59.999 --> 99:59:59.999 even though we're way the heck up on the roadside. 99:59:59.999 --> 99:59:59.999 There you can see down to the beach. 99:59:59.999 --> 99:59:59.999 Alright, that's it. Bye for now.