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TPO 7 Lecture 3 Anthropology 04:45

Anthropology , archeology, paleontology/ palaeontology

Native, local , aborigine原生種 , aboriginal

Region , area , district

focus on Iroquois and Hooray (Huron) peoples. They lived in the northeastern great lakes region of

North America. Now, back then, their lives depended on the natural resources of the

forests, especially the birch tree. The birch tree can grow in many different types of soils

and it's prevalent in that area. Now can anyone here describe the birch tree?

Stu: They are tall and white, the bark, I mean.

Pro: Yes. The birch tree has white bark, and this tough protective outer layer of the tree,

this white bark, is waterproof. And this waterproof quality of the bark, it made it useful for

** things like cooking containers, a variety of utensils. And if you peel birch bark in

the winter, we call it ‗the winter bark', another layer a tougher inner layer of the tree

adheres to the bark, producing a stronger material. So the winter bark was used for larger

utensils and containers.

Stu: I know people make utensils out of wood, but utensils out of tree bark?

Pro: Well, birch bark is pliable and very easy to bend. The Native Americans would cut

the bark and fold it into any shape they needed, then secure with cords until it dried. They

could fold the bark into many shapes.

Stu: So if they cooked in bowls made of birch bark, wouldn't that make the food taste

funny?

Pro: Oh, that's one of the great things of birch bark. The taste of the birch tree doesn't get

transferred to the food. So it was perfect for cooking containers. But the most important

use of the bark, by far, was the canoe. Since the northeastern region of North American is

interconnected by many streams and waterways, water transportation by vessels like a

canoe was most essential. The paths through the woods were often over-grown, so water

travel was much faster. And here's what the Native Americans did. They would peel large

sheets of bark from the tree to form light-weight yet sturdy canoes. The bark was

stretched over frames made from tree branches, stitched together and sealed with resin

（current, currant, resin, raisin ; any of several viscous organic substances derived from plants）.

You know that sticky liquid that comes out of the tree? And when it dries, it's watertight.

One great thing of these birch bark canoes was that they could carry a large amount of

cargo. For example, a canoe weighing about 50 pounds could carry up to nine people and

250 pounds of cargo.

Stu: Wow! But how far could they drive that way?

Pro: Well like I said, the northeastern region is interconnected by rivers and streams and

the ocean at the coast. The canoes allow them to travel over a vast area that today it

would take a few hours to fly over. You see, the Native Americans made canoes of all

types, for travel on small streams or on large open ocean waters. For small streams, they

made narrow, maneuverable boats, while a large canoe was needed for the ocean. They

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could travel throughout the area only occasionally having to portage, to carry the canoe

over a land short distance to another nearby stream. And since the canoes were so light,

this wasn't a difficult task. Now how do you think this affected their lives?

Stu: Well if they could travel so easily over such a large area, they could trade with people

from other areas which I guess would lead them to form alliances?

Pro: Exactly. Having an efficient means of transportation, well, that helps the Iroquois to

form a federation linked by natural waterways. And this federation expanded from what is

now Southern Canada all the way south to the Dalever River. And this efficiency of birch

bark canoe also made an impression on (impressed) newcomers of the area. French traders in the 17 century modeled their...well they adopted the design of Iroquois birch bark canoes, and

they found they could travel great distances more than 15 hundred kilometers a month. Now

besides the bark, Native Americans also used the wood of the birch tree. The young trees

were used to support for loggings with the waterproof bark used as roofing. Branches

were folded into snow shoes and the Native American people were all adept to running

very fast over the snow in these birch brand snow shoes which if you ever tried walking in

snow shoes you know wasn't easy.

L

TPO 7 Lecture 4 Geology 11:50

Last time, we started to talk about the glaciers, and how these masses(large amount of unspecified size) ice forms from crystallized snow, and some of you were amazed at how huge

some of the these glaciers are. Now, even though it may be difficult to

understand how a huge mass less can move or flow, in another word for it, it‘s

really known that the secret that the glaciers flow, because of gravity. But how

they flow, and why they flow needs some explaining. Now, the first type of the

glaciers flow is called: basal slip.

Basal slip or its sliding as it‘s often called, basically refers to the slipping or

sliding of glacier across bedrock, actually across the thin layer of water, on top

of the bedrock. So, this process shouldn‘t be too hard to imagine. What

happens is that the ice of the base of the glacier is under gradual depression--the depression coming from the weights of the overlaying ice. And you

probably know that the under pressure, the melting temperature of water as

the ice I mean, is reduced. So, ice at the basis(bases) of glacier melts, even though it‘s

below zero degree (Celsius / Fahrenheit ) thaws. And this results in thin layer of water between the

glacier and ground. This layer of water reduces friction is... is like a lubricant.

And it allows the glacier to slat/slide or slip over the bedrock.

Ok, now the next type movement we will talk about is called: deformation. You

already known that the ice brittle, if you heated with hammer, it will shatter

glass. But ice also plastic(flexible / pliable ), you can change the shapes without breaking. If you

leave, for example, a bar of ice supported only at one end, they end, they

unsupported end will deform under its own way due---kind of flatten out one in

to get stored it deformed it. Think deformation a very slow oozing(ooze

v. flow slowly; emit, discharge, give off light or liquid; leak information; exude, radiate

). Depending on the stresses on the glacier, the ice crystal was in the re-organized. And

during this re-organization the ice crystal re-allied in a way that allows them to

slide pass each other. And so the glacier oozes downhill without any ice

actually melting.

Now, there are a couple of the factors that affects the

amounts of deformation that takes place or the speed of the glaciers

movement for example. Deformation is more likely to occur the thicker the ices,

because at the gravity of the weight its ice. And temperature also plays part

here, in that XXcold ice does not moves easily. As the ice that is close to the mounting

points, in fact, it is not to different from… the weight oil is, thicker at the lower

temperature. So, if you had a glacier in the slightly warmer region, it will flow

faster than the glacier in the cooler region.

Ok, um… Now, let‘s touch briefly on extension and compression. You textbook

includes this as type as a particular type of glacier movement, but you will see

that these are … cause many textbooks that omitted as type of movement as

included. And I might not include right now, if there won‘t in your textbooks. But,

basically, the upper parts of the glacier have less pressure on them. So, they

don‘t deform easily, they tend to be more brittle. And crevasses (crevice, fissure)can form in this

upper layer of glacier. When the glacier comes into contact with bedrock walls

or the otherwise under some kinds of stresses, but can (can’t)deform quickly enough.

So, the ice would expand or constrict, and that can cause XXX the fissures be crack to

form in the surface of the layer of ice, and that brittle the surface ice moving, is

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sometimes considered a type of glacier movement depending on which source

you can thaw(consult) to. Now, as you probably know, glaciers generally move really

slowly. But sometimes, they experience surges, and during these surges, in

some places, they can move its speeds as high as 7000 meters per year. Now,

a speed like that are pretty unusual, 100 of times faster than the regular

movement of glaciers, but you can actually see glacier move during these

surges, though it is rare.