1
99:59:59,999 --> 99:59:59,999
Okay, so this is the difference between uh, glacial till,

2
99:59:59,999 --> 99:59:59,999
which is unstratified,

3
99:59:59,999 --> 99:59:59,999
and non-glacial till.

4
99:59:59,999 --> 99:59:59,999
So, hopefully you can see that this uh, gravel here

5
99:59:59,999 --> 99:59:59,999
is well-stratified.

6
99:59:59,999 --> 99:59:59,999
There are a lot of sedimentary features here.

7
99:59:59,999 --> 99:59:59,999
Um, you can see graded bedding.

8
99:59:59,999 --> 99:59:59,999
You can also see cross bedding.

9
99:59:59,999 --> 99:59:59,999
Maybe I can just sort of zoom in on that.

10
99:59:59,999 --> 99:59:59,999
So there's cross bedding right there.

11
99:59:59,999 --> 99:59:59,999
Very coarse uh, cross bedding.

12
99:59:59,999 --> 99:59:59,999
However, the stratification or the horizontal layering,

13
99:59:59,999 --> 99:59:59,999
the general horizontal here,

14
99:59:59,999 --> 99:59:59,999
indicates that this is not glacial gravel.

15
99:59:59,999 --> 99:59:59,999
Even though it's approximately the correct size

16
99:59:59,999 --> 99:59:59,999
and sorting distribution.

17
99:59:59,999 --> 99:59:59,999
The presence of sedimentary features

18
99:59:59,999 --> 99:59:59,999
as well as uh, the stratification,

19
99:59:59,999 --> 99:59:59,999
that's the horizontal layering,

20
99:59:59,999 --> 99:59:59,999
indicated as not glacial gravel.

21
99:59:59,999 --> 99:59:59,999
Okay. I'll try and show you glacial gravel a little later.

22
99:59:59,999 --> 99:59:59,999
So this is uh, glacial till.

23
99:59:59,999 --> 99:59:59,999
It is gravel that is deposited by a glacier.

24
99:59:59,999 --> 99:59:59,999
Um, and the identifying characteristics of it

25
99:59:59,999 --> 99:59:59,999
is well-rounded clasts,

26
99:59:59,999 --> 99:59:59,999
however they're not really really well-rounded.

27
99:59:59,999 --> 99:59:59,999
They are definitely rounded to some extent.

28
99:59:59,999 --> 99:59:59,999
Um, oftentimes there are striations on each individual clast,

29
99:59:59,999 --> 99:59:59,999
maybe I can show you that later.

30
99:59:59,999 --> 99:59:59,999
Um, those are scratches that are produced

31
99:59:59,999 --> 99:59:59,999
when gravel bounces or scrapes against

32
99:59:59,999 --> 99:59:59,999
other pieces of gravel or the bedrock.

33
99:59:59,999 --> 99:59:59,999
And the other identifying characteristic

34
99:59:59,999 --> 99:59:59,999
is that the gravel itself is unstratified.

35
99:59:59,999 --> 99:59:59,999
There is no layering, no horizontal stratification.

36
99:59:59,999 --> 99:59:59,999
Um, and there really are no sedimentary features here,

37
99:59:59,999 --> 99:59:59,999
other than the lack of sedimentary features,

38
99:59:59,999 --> 99:59:59,999
which indicates that it was deposited by a glacier.

39
99:59:59,999 --> 99:59:59,999
Now hopefully you'll be able to see,

40
99:59:59,999 --> 99:59:59,999
if it'll focus on that,

41
99:59:59,999 --> 99:59:59,999
the scratches on the surface of this clast.

42
99:59:59,999 --> 99:59:59,999
Those parallel scratches are glacial striations,

43
99:59:59,999 --> 99:59:59,999
which are present on a clast.

44
99:59:59,999 --> 99:59:59,999
It's stuck in there pretty hard. Argghh.

45
99:59:59,999 --> 99:59:59,999
It won't come out.

46
99:59:59,999 --> 99:59:59,999
And in addition to the lack of uh, sedimentary features,

47
99:59:59,999 --> 99:59:59,999
um, one of the characteristics that you always look for

48
99:59:59,999 --> 99:59:59,999
is a very very poor degree of sorting

49
99:59:59,999 --> 99:59:59,999
in terms of clast size.

50
99:59:59,999 --> 99:59:59,999
And so, maybe I can zoom in on that a little bit.

51
99:59:59,999 --> 99:59:59,999
You've got clasts of all different, uh, sizes.

52
99:59:59,999 --> 99:59:59,999
Very poorly distributed.

53
99:59:59,999 --> 99:59:59,999
I suppose even down to these sizes,

54
99:59:59,999 --> 99:59:59,999
which have fallen down from the cliff face, I suppose,

55
99:59:59,999 --> 99:59:59,999
the gravel face anyways.

56
99:59:59,999 --> 99:59:59,999
Very poor sorting.

57
99:59:59,999 --> 99:59:59,999
Okay. Since we're talking about till,

58
99:59:59,999 --> 99:59:59,999
I thought I'd show you what happens when till, um,

59
99:59:59,999 --> 99:59:59,999
becomes a rock, when it comes consolidated or indurated.

60
99:59:59,999 --> 99:59:59,999
This is called tillite, which is uh,

61
99:59:59,999 --> 99:59:59,999
the rock, I suppose, from glacial till, a conglomerate.

62
99:59:59,999 --> 99:59:59,999
This one is very old.

63
99:59:59,999 --> 99:59:59,999
It is on the side of the Trans Canada, here. [cars going by]

64
99:59:59,999 --> 99:59:59,999
As you can tell by the traffic.

65
99:59:59,999 --> 99:59:59,999
And it is south of Wawa in Ontario, Canada.

66
99:59:59,999 --> 99:59:59,999
[traffic in background]

67
99:59:59,999 --> 99:59:59,999
This particular crop has been highly metamorphosed,

68
99:59:59,999 --> 99:59:59,999
so these in the Canadian shield.

69
99:59:59,999 --> 99:59:59,999
Um, so strongly metamorphosed.

70
99:59:59,999 --> 99:59:59,999
And this tillite is uh, weathering very rapidly

71
99:59:59,999 --> 99:59:59,999
as a result of the intense metamorphism,

72
99:59:59,999 --> 99:59:59,999
which has caused cracks and fractures

73
99:59:59,999 --> 99:59:59,999
which increase surface area, of course,

74
99:59:59,999 --> 99:59:59,999
and cause weathering to accelerate.

75
99:59:59,999 --> 99:59:59,999
[traffic in background]

76
99:59:59,999 --> 99:59:59,999
Now realize I'm looking at a shadow here,

77
99:59:59,999 --> 99:59:59,999
but hopefully you can see that the clasts are well-rounded.

78
99:59:59,999 --> 99:59:59,999
Very poorly sorted, in terms of size distribution.

79
99:59:59,999 --> 99:59:59,999
And are not layered. They are unstratified.

80
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.

81
99:59:59,999 --> 99:59:59,999
That is Lake Superior,

82
99:59:59,999 --> 99:59:59,999
about an hour south of Wawa, Ontario.

83
99:59:59,999 --> 99:59:59,999
Pretty big lake, eh? Kind of looks like the ocean.

84
99:59:59,999 --> 99:59:59,999
You can't see the other side of Lake Superior,

85
99:59:59,999 --> 99:59:59,999
even though we're way the heck up on the roadside.

86
99:59:59,999 --> 99:59:59,999
There you can see down to the beach.

87
99:59:59,999 --> 99:59:59,999
Alright, that's it. Bye for now.