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Many of the higher mountains of the world have rivers of ice flowing for some distance down their sides. You wonder how they were formed?

If you squeeze a snowball very hard and work it for some time with your hands, it becomes almost a ball of ice. This is caused by the pressure and warmth of your hands.

In mountainous localities where there is a great fall of snow, the snow does not all disappear through the summer months. More snow falls each winter for several years than can melt during the summer, so that the depth is constantly increasing. The great weight of this accumulation, together with the heat from

the sun's rays, causes the snow to change to ice. This ice forms into streams which flow slowly down the mountain sides. Ice streams tear up trees, plants, and soil, and break off large rock masses in

their descent. They carry these in the ice to lower, warmer sections, where the

ice melts, leaving the rock fragments and other material strewn over the ground. Large rivers full of fine soil come from these ice streams. The soil is carried to the floodplain or to the sea. Many gravel and sand hills are formed by the material brought down by these rivers.

[graphic]

Rains wash the sand from these sand

hills to the lower land, covering it with a sandy, barren soil.

Glaciers, or ice rivers, are in Alaska, Greenland, western Canada and United States, and on the mountains of Europe, South America, and Asia.

There was a time in the Earth's history when the cold belts extended much farther towards the

Equator than at the present time. After many, many years there was a great accumulation of snow. Through pressure and heat this snow changed to ice, and flowed slowly down the slopes in streams, spread out on the plains in a broad, continuous

or

sheet of ice. This ice sheet covered all of the northern parts of North America and Europe,

extending across the continent of North America in a westerly direction from New Jersey.

courses down the mountain side. Many people visit the regions where the ice

How do we know that there were once rivers and ice sheets now are. They do this

ice-sheets

in the

[graphic]

world? We

know this

because of

the great amount of material

which was

left when

the ice was

melted by the warmer weather.

Large pieces

of rocks,

which we

call bowlders, were left

because of the grandeur and beauty

which they present, and also because the history of the past conditions may be read through what is taking place to-day.

The ice from some of the glaciers of to-day is utilized by man as an article of trade. Men cut it into blocks and transport it to cities, where it is sold to supply people with ice during the

summer

months.

When the

strewn over the surface at this time. ice river descends to the sea the weight

Do you know of any bowlders in your school district?

In some cases the valleys were filled and the mountains completely buried by this mate

[blocks in formation]

of the ice, together with the pressure of the water underneath, causes great masses of ice to break off.

These are icebergs.

They float

away, and are dan gerous to steamers

and boats because of

their great bulk. (P. 117.)

[graphic]

Describe each of the pictures. Note the great chasms or gorges in the ice which make traveling over the glaciers very dangerous. Visit sand hills,

clay beds, and bowlder-strewn surfaces. Learn all you can about them. Describe and sketch them.

Here is the picture of a lake. It lies in the lowest part of a hollow in the land surface high up in the mountains. The entire hollow is a lake basin. The lake is

fed by the streams which form from the rains and melting snow, and flow down the inside slopes of the basin. The land which borders the water of a lake is a lake shore. The shore-line is the line where the land slopes under the water. The higher and lower land of the lake shore

causes many irregularities

in the shore-line. In places where the shores are high the land projects out into the water; in places where the shore is low the water flows over the land, making indenta tions of the lake into the land.

If you could look down on this lake you should see its true shape or map. Trace the shore-line of the lake pictures. Tell where there are projections and indentations. Model this lake-basin.

On the next page is the picture of a lake which lies in a basin in the lowland. Tell how this lowland lake basin differs from the mountain lake basin. Trace its shore-line. Tell what plants are growing on its shore. What evidences of life are there?

[graphic]

MAP OF A MOUNTAIN LAKE.

On the next

page there are pictures of ponds; one is in the mountains, and one

is in the lowlands.

Trace around each. Trace the slopes of each. What evidences of life are there in these pictures?

You

see

ponds are like lakes in form, only they are

smaller.

A l l

LAKES and

PONDS are

fed by

streams

and springs. Some lakes

and some ponds have only one large feeder.

Lakes and ponds usually have OUTLETS

Tell which part is occupied by the lake. Represent which carry the water away from them to

the streams which feed it.

lower land and to the sea.

The feeders are usually muddy. This

is because they carry a great deal of soil.

They carry much more soil during heavy rains or melting snows

than at any other time. The dirt or soil is washed from the mountain sides as the streams descend to the

All lakes and ponds of the world are filling up.

[graphic]

We can find

old lake bot

toms in almost

any locality. Observe the pictures on the next page. Both are fine illustrations of a lake basin in the process of filling. You see villages are

built on the mud plains.

During flood-time the hollows occupied by the lakes and ponds are completely filled with water. The water often reaches far up on the shore. In the highland region the basin overflows at its lowest point and the water flows away to lower land. The

A LOWLAND LAKE.

[graphic]

lake.

This soil settles in the bottom of that part of the pond or lake which is nearest the entrance of the stream.

Streams continue to carry soil to the pond or lake until it is filled up. It first becomes swampy, and then a solid, fertile plain. Such plains are usually drained by one or more

streams.

A LOWLAND POND.

water from the lake in the lowland spreads far out over the low-lying land.

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